Patch that refactors global read lock implementation and fixes

bug #57006 "Deadlock between HANDLER and FLUSH TABLES WITH READ
LOCK" and bug #54673 "It takes too long to get readlock for
'FLUSH TABLES WITH READ LOCK'".

The first bug manifested itself as a deadlock which occurred
when a connection, which had some table open through HANDLER
statement, tried to update some data through DML statement
while another connection tried to execute FLUSH TABLES WITH
READ LOCK concurrently.

What happened was that FTWRL in the second connection managed
to perform first step of GRL acquisition and thus blocked all
upcoming DML. After that it started to wait for table open
through HANDLER statement to be flushed. When the first connection
tried to execute DML it has started to wait for GRL/the second
connection creating deadlock.

The second bug manifested itself as starvation of FLUSH TABLES
WITH READ LOCK statements in cases when there was a constant
stream of concurrent DML statements (in two or more
connections).

This has happened because requests for protection against GRL
which were acquired by DML statements were ignoring presence of
pending GRL and thus the latter was starved.

This patch solves both these problems by re-implementing GRL
using metadata locks.

Similar to the old implementation acquisition of GRL in new
implementation is two-step. During the first step we block
all concurrent DML and DDL statements by acquiring global S
metadata lock (each DML and DDL statement acquires global IX
lock for its duration). During the second step we block commits
by acquiring global S lock in COMMIT namespace (commit code
acquires global IX lock in this namespace).

Note that unlike in old implementation acquisition of
protection against GRL in DML and DDL is semi-automatic.
We assume that any statement which should be blocked by GRL
will either open and acquires write-lock on tables or acquires
metadata locks on objects it is going to modify. For any such
statement global IX metadata lock is automatically acquired
for its duration.

The first problem is solved because waits for GRL become
visible to deadlock detector in metadata locking subsystem
and thus deadlocks like one in the first bug become impossible.

The second problem is solved because global S locks which
are used for GRL implementation are given preference over
IX locks which are acquired by concurrent DML (and we can
switch to fair scheduling in future if needed).

Important change:
FTWRL/GRL no longer blocks DML and DDL on temporary tables.
Before this patch behavior was not consistent in this respect:
in some cases DML/DDL statements on temporary tables were
blocked while in others they were not. Since the main use cases
for FTWRL are various forms of backups and temporary tables are
not preserved during backups we have opted for consistently
allowing DML/DDL on temporary tables during FTWRL/GRL.

Important change:
This patch changes thread state names which are used when
DML/DDL of FTWRL is waiting for global read lock. It is now
either "Waiting for global read lock" or "Waiting for commit
lock" depending on the stage on which FTWRL is.

Incompatible change:
To solve deadlock in events code which was exposed by this
patch we have to replace LOCK_event_metadata mutex with
metadata locks on events. As result we have to prohibit
DDL on events under LOCK TABLES.

This patch also adds extensive test coverage for interaction
of DML/DDL and FTWRL.

Performance of new and old global read lock implementations
in sysbench tests were compared. There were no significant
difference between new and old implementations.

mysql-test/include/check_ftwrl_compatible.inc:
  Added helper script which allows to check that a statement is
  compatible with FLUSH TABLES WITH READ LOCK.
mysql-test/include/check_ftwrl_incompatible.inc:
  Added helper script which allows to check that a statement is
  incompatible with FLUSH TABLES WITH READ LOCK.
mysql-test/include/handler.inc:
  Adjusted test case to the fact that now DROP TABLE closes
  open HANDLERs for the table to be dropped before checking
  if there active FTWRL in this connection.
mysql-test/include/wait_show_condition.inc:
  Fixed small error in the timeout message. The correct name
  of variable used as parameter for this script is "$condition"
  and not "$wait_condition".
mysql-test/r/delayed.result:
  Added test coverage for scenario which triggered assert in
  metadata locking subsystem.
mysql-test/r/events_2.result:
  Updated test results after prohibiting event DDL operations
  under LOCK TABLES.
mysql-test/r/flush.result:
  Added test coverage for bug #57006 "Deadlock between HANDLER
  and FLUSH TABLES WITH READ LOCK".
mysql-test/r/flush_read_lock.result:
  Added test coverage for various aspects of FLUSH TABLES WITH
  READ LOCK functionality.
mysql-test/r/flush_read_lock_kill.result:
  Adjusted test case after replacing custom global read lock
  implementation with one based on metadata locks. Use new
  debug_sync point. Do not disable concurrent inserts as now
  InnoDB we always use InnoDB table.
mysql-test/r/handler_innodb.result:
  Adjusted test case to the fact that now DROP TABLE closes
  open HANDLERs for the table to be dropped before checking
  if there active FTWRL in this connection.
mysql-test/r/handler_myisam.result:
  Adjusted test case to the fact that now DROP TABLE closes
  open HANDLERs for the table to be dropped before checking
  if there active FTWRL in this connection.
mysql-test/r/mdl_sync.result:
  Adjusted test case after replacing custom global read lock
  implementation with one based on metadata locks. Replaced
  usage of GRL-specific debug_sync's with appropriate sync
  points in MDL subsystem.
mysql-test/suite/perfschema/r/dml_setup_instruments.result:
  Updated test results after removing global
  COND_global_read_lock condition variable.
mysql-test/suite/perfschema/r/func_file_io.result:
  Ensure that this test doesn't affect subsequent tests.
  At the end of its execution enable back P_S instrumentation
  which this test disables at some point.
mysql-test/suite/perfschema/r/func_mutex.result:
  Ensure that this test doesn't affect subsequent tests.
  At the end of its execution enable back P_S instrumentation
  which this test disables at some point.
mysql-test/suite/perfschema/r/global_read_lock.result:
  Adjusted test case to take into account that new GRL
  implementation is based on MDL.
mysql-test/suite/perfschema/r/server_init.result:
  Adjusted test case after replacing custom global read
  lock implementation with one based on MDL and replacing
  LOCK_event_metadata mutex with metadata lock.
mysql-test/suite/perfschema/t/func_file_io.test:
  Ensure that this test doesn't affect subsequent tests.
  At the end of its execution enable back P_S instrumentation
  which this test disables at some point.
mysql-test/suite/perfschema/t/func_mutex.test:
  Ensure that this test doesn't affect subsequent tests.
  At the end of its execution enable back P_S instrumentation
  which this test disables at some point.
mysql-test/suite/perfschema/t/global_read_lock.test:
  Adjusted test case to take into account that new GRL
  implementation is based on MDL.
mysql-test/suite/perfschema/t/server_init.test:
  Adjusted test case after replacing custom global read
  lock implementation with one based on MDL and replacing
  LOCK_event_metadata mutex with metadata lock.
mysql-test/suite/rpl/r/rpl_tmp_table_and_DDL.result:
  Updated test results after prohibiting event DDL under
  LOCK TABLES.
mysql-test/t/delayed.test:
  Added test coverage for scenario which triggered assert in
  metadata locking subsystem.
mysql-test/t/events_2.test:
  Updated test case after prohibiting event DDL operations
  under LOCK TABLES.
mysql-test/t/flush.test:
  Added test coverage for bug #57006 "Deadlock between HANDLER
  and FLUSH TABLES WITH READ LOCK".
mysql-test/t/flush_block_commit.test:
  Adjusted test case after changing thread state name which
  is used when COMMIT waits for FLUSH TABLES WITH READ LOCK
  from "Waiting for release of readlock" to "Waiting for commit
  lock".
mysql-test/t/flush_block_commit_notembedded.test:
  Adjusted test case after changing thread state name which is
  used when DML waits for FLUSH TABLES WITH READ LOCK. Now we
  use "Waiting for global read lock" in this case.
mysql-test/t/flush_read_lock.test:
  Added test coverage for various aspects of FLUSH TABLES WITH
  READ LOCK functionality.
mysql-test/t/flush_read_lock_kill-master.opt:
  We no longer need to use make_global_read_lock_block_commit_loop
  debug tag in this test. Instead we rely on an appropriate
  debug_sync point in MDL code.
mysql-test/t/flush_read_lock_kill.test:
  Adjusted test case after replacing custom global read lock
  implementation with one based on metadata locks. Use new
  debug_sync point. Do not disable concurrent inserts as now
  InnoDB we always use InnoDB table.
mysql-test/t/lock_multi.test:
  Adjusted test case after changing thread state names which
  are used when DML or DDL waits for FLUSH TABLES WITH READ
  LOCK to "Waiting for global read lock".
mysql-test/t/mdl_sync.test:
  Adjusted test case after replacing custom global read lock
  implementation with one based on metadata locks. Replaced
  usage of GRL-specific debug_sync's with appropriate sync
  points in MDL subsystem. Updated thread state names which
  are used when DDL waits for FTWRL.
mysql-test/t/trigger_notembedded.test:
  Adjusted test case after changing thread state names which
  are used when DML or DDL waits for FLUSH TABLES WITH READ
  LOCK to "Waiting for global read lock".
sql/event_data_objects.cc:
  Removed Event_queue_element::status/last_executed_changed
  members and Event_queue_element::update_timing_fields()
  method. We no longer use this class for updating mysql.events
  once event is chosen for execution. Accesses to instances of
  this class in scheduler thread require protection by
  Event_queue::LOCK_event_queue mutex and we try to avoid
  updating table while holding this lock.
sql/event_data_objects.h:
  Removed Event_queue_element::status/last_executed_changed
  members and Event_queue_element::update_timing_fields()
  method. We no longer use this class for updating mysql.events
  once event is chosen for execution. Accesses to instances of
  this class in scheduler thread require protection by
  Event_queue::LOCK_event_queue mutex and we try to avoid
  updating table while holding this lock.
sql/event_db_repository.cc:
  - Changed Event_db_repository methods to not release all
    metadata locks once they are done updating mysql.events
    table. This allows to keep metadata lock protecting
    against GRL and lock protecting particular event around
    until corresponding DDL statement is written to the binary
    log.
  - Removed logic for conditional update of "status" and
    "last_executed" fields from update_timing_fields_for_event()
    method. In the only case when this method is called now
    "last_executed" is always modified and tracking change
    of "status" is too much hassle.
sql/event_db_repository.h:
  Removed logic for conditional update of "status" and
  "last_executed" fields from Event_db_repository::
  update_timing_fields_for_event() method.
  In the only case when this method is called now "last_executed"
  is always modified and tracking change of "status" field is
  too much hassle.
sql/event_queue.cc:
  Changed event scheduler code not to update mysql.events
  table while holding Event_queue::LOCK_event_queue mutex.
  Doing so led to a deadlock with a new GRL implementation.
  This deadlock didn't occur with old implementation due to
  fact that code acquiring protection against GRL ignored
  pending GRL requests (which lead to GRL starvation).
  One of goals of new implementation is to disallow GRL
  starvation and so we have to solve problem with this
  deadlock in a different way.
sql/events.cc:
  Changed methods of Events class to acquire protection
  against GRL while perfoming DDL statement and keep it
  until statement is written to the binary log.
  Unfortunately this step together with new GRL implementation
  exposed deadlock involving Events::LOCK_event_metadata
  and GRL. To solve it Events::LOCK_event_metadata mutex was
  replaced with a metadata lock on event. As a side-effect
  events DDL has to be prohibited under LOCK TABLES even in
  cases when mysql.events table was explicitly locked for
  write.
sql/events.h:
  Replaced Events::LOCK_event_metadata mutex with a metadata
  lock on event.
sql/ha_ndbcluster.cc:
  Updated code after replacing custom global read lock
  implementation with one based on MDL. Since MDL subsystem
  should now be able to detect deadlocks involving metadata
  locks and GRL there is no need for special handling of
  active GRL.
sql/handler.cc:
  Replaced custom implementation of global read lock with
  one based on metadata locks. Consequently when doing
  commit instead of calling method of Global_read_lock
  class to acquire protection against GRL we simply acquire
  IX in COMMIT namespace.
sql/lock.cc:
  Replaced custom implementation of global read lock with
  one based on metadata locks. This step allows to expose
  wait for GRL to deadlock detector of MDL subsystem and
  thus succesfully resolve deadlocks similar to one behind
  bug #57006 "Deadlock between HANDLER and FLUSH TABLES
  WITH READ LOCK". It also solves problem with GRL starvation
  described in bug #54673 "It takes too long to get readlock
  for 'FLUSH TABLES WITH READ LOCK'" since metadata locks used
  by GRL give preference to FTWRL statement instead of DML
  statements (if needed in future this can be changed to
  fair scheduling).
  
  Similar to old implementation of acquisition of GRL is
  two-step. During the first step we block all concurrent
  DML and DDL statements by acquiring global S metadata lock
  (each DML and DDL statement acquires global IX lock for
  its duration). During the second step we block commits by
  acquiring global S lock in COMMIT namespace (commit code
  acquires global IX lock in this namespace).
  
  Note that unlike in old implementation acquisition of
  protection against GRL in DML and DDL is semi-automatic.
  We assume that any statement which should be blocked by GRL
  will either open and acquires write-lock on tables or acquires
  metadata locks on objects it is going to modify. For any such
  statement global IX metadata lock is automatically acquired
  for its duration.
  
  To support this change:
  - Global_read_lock::lock/unlock_global_read_lock and
    make_global_read_lock_block_commit methods were changed
    accordingly.
  - Global_read_lock::wait_if_global_read_lock() and
    start_waiting_global_read_lock() methods were dropped.
    It is now responsibility of code acquiring metadata locks
    opening tables to acquire protection against GRL by
    explicitly taking global IX lock with statement duration.
  - Global variables, mutex and condition variable used by
    old implementation was removed.
  - lock_routine_name() was changed to use statement duration for
    its global IX lock. It was also renamed to lock_object_name()
    as it now also used to take metadata locks on events.
  - Global_read_lock::set_explicit_lock_duration() was added which
    allows not to release locks used for GRL when leaving prelocked
    mode.
sql/lock.h:
  - Renamed lock_routine_name() to lock_object_name() and changed
    its signature to allow its usage for events.
  - Removed broadcast_refresh() function. It is no longer needed
    with new GRL implementation.
sql/log_event.cc:
  Release metadata locks with statement duration at the end
  of processing legacy event for LOAD DATA. This ensures that
  replication thread processing such event properly releases
  its protection against global read lock.
sql/mdl.cc:
  Changed MDL subsystem to support new MDL-based implementation
  of global read lock.
  
  Added COMMIT and EVENTS namespaces for metadata locks. Changed
  thread state name for GLOBAL namespace to "Waiting for global
  read lock".
  
  Optimized MDL_map::find_or_insert() method to avoid taking
  m_mutex mutex when looking up MDL_lock objects for GLOBAL
  or COMMIT namespaces. We keep pre-created MDL_lock objects
  for these namespaces around and simply return pointers to
  these global objects when needed.
  
  Changed MDL_lock/MDL_scoped_lock to properly handle
  notification of insert delayed handler threads when FTWRL
  takes global S lock.
  
  Introduced concept of lock duration. In addition to locks with
  transaction duration which work in the way which is similar to
  how locks worked before (i.e. they are released at the end of
  transaction), locks with statement and explicit duration were
  introduced.
  Locks with statement duration are automatically released at the
  end of statement. Locks with explicit duration require explicit
  release and obsolete concept of transactional sentinel.
  
  * Changed MDL_request and MDL_ticket classes to support notion
    of duration.
  * Changed MDL_context to keep locks with different duration in
    different lists. Changed code handling ticket list to take
    this into account.
  * Changed methods responsible for releasing locks to take into
    account duration of tickets. Particularly public
    MDL_context::release_lock() method now only can release
    tickets with explicit duration (there is still internal
    method which allows to specify duration). To release locks
    with statement or transaction duration one have to use
    release_statement/transactional_locks() methods.
  * Concept of savepoint for MDL subsystem now has to take into
    account locks with statement duration. Consequently
    MDL_savepoint class was introduced and methods working with
    savepoints were updated accordingly.
  * Added methods which allow to set duration for one or all
    locks in the context.
sql/mdl.h:
  Changed MDL subsystem to support new MDL-based implementation
  of global read lock.
  
  Added COMMIT and EVENTS namespaces for metadata locks.
  
  Introduced concept of lock duration. In addition to locks with
  transaction duration which work in the way which is similar to
  how locks worked before (i.e. they are released at the end of
  transaction), locks with statement and explicit duration were
  introduced.
  Locks with statement duration are automatically released at the
  end of statement. Locks with explicit duration require explicit
  release and obsolete concept of transactional sentinel.
  
  * Changed MDL_request and MDL_ticket classes to support notion
    of duration.
  * Changed MDL_context to keep locks with different duration in
    different lists. Changed code handling ticket list to take
    this into account.
  * Changed methods responsible for releasing locks to take into
    account duration of tickets. Particularly public
    MDL_context::release_lock() method now only can release
    tickets with explicit duration (there is still internal
    method which allows to specify duration). To release locks
    with statement or transaction duration one have to use
    release_statement/transactional_locks() methods.
  * Concept of savepoint for MDL subsystem now has to take into
    account locks with statement duration. Consequently
    MDL_savepoint class was introduced and methods working with
    savepoints were updated accordingly.
  * Added methods which allow to set duration for one or all
    locks in the context.
sql/mysqld.cc:
  Removed global mutex and condition variables which were used
  by old implementation of GRL.
  Also we no longer need to initialize Events::LOCK_event_metadata
  mutex as it was replaced with metadata locks on events.
sql/mysqld.h:
  Removed global variable, mutex and condition variables which
  were used by old implementation of GRL.
sql/rpl_rli.cc:
  When slave thread closes tables which were open for handling
  of RBR events ensure that it releases global IX lock which
  was acquired as protection against GRL.
sql/sp.cc:
  Adjusted code to the new signature of lock_object/routine_name(),
  to the fact that one now needs specify duration of lock when
  initializing MDL_request and to the fact that savepoints for MDL
  subsystem are now represented by MDL_savepoint class.
sql/sp_head.cc:
  Ensure that statements in stored procedures release statement
  metadata locks and thus release their protectiong against GRL
  in proper moment in time.
  Adjusted code to the fact that one now needs specify duration
  of lock when initializing MDL_request.
sql/sql_admin.cc:
  Adjusted code to the fact that one now needs specify duration
  of lock when initializing MDL_request.
sql/sql_base.cc:
  - Implemented support for new approach to acquiring protection
    against global read lock. We no longer acquire such protection
    explicitly on the basis of statement flags. Instead we always
    rely on code which is responsible for acquiring metadata locks
    on object to be changed acquiring this protection. This is
    achieved by acquiring global IX metadata lock with statement
    duration. Code doing this also responsible for checking that
    current connection has no active GRL by calling an
    Global_read_lock::can_acquire_protection() method.
    Changed code in open_table() and lock_table_names()
    accordingly.
    Note that as result of this change DDL and DML on temporary
    tables is always compatible with GRL (before it was
    incompatible in some cases and compatible in other cases).
  - To speed-up code acquiring protection against GRL introduced
    m_has_protection_against_grl member in Open_table_context
    class. It indicates that protection was already acquired
    sometime during open_tables() execution and new attempts
    can be skipped.
  - Thanks to new GRL implementation calls to broadcast_refresh()
    became unnecessary and were removed.
  - Adjusted code to the fact that one now needs specify duration
    of lock when initializing MDL_request and to the fact that
    savepoints for MDL subsystem are now represented by
    MDL_savepoint class.
sql/sql_base.h:
  Adjusted code to the fact that savepoints for MDL subsystem are
  now represented by MDL_savepoint class.
  Also introduced Open_table_context::m_has_protection_against_grl
  member which allows to avoid acquiring protection against GRL
  while opening tables if such protection was already acquired.
sql/sql_class.cc:
  Changed THD::leave_locked_tables_mode() after transactional
  sentinel for metadata locks was obsoleted by introduction of
  locks with explicit duration.
sql/sql_class.h:
  - Adjusted code to the fact that savepoints for MDL subsystem
    are now represented by MDL_savepoint class.
  - Changed Global_read_lock class according to changes in
    global read lock implementation:
    * wait_if_global_read_lock and start_waiting_global_read_lock
      are now gone. Instead code needing protection against GRL
      has to acquire global IX metadata lock with statement
      duration itself. To help it new can_acquire_protection()
      was introduced. Also as result of the above change
      m_protection_count member is gone too.
    * Added m_mdl_blocks_commits_lock member to store metadata
      lock blocking commits.
    * Adjusted code to the fact that concept of transactional
      sentinel was obsoleted by concept of lock duration.
  - Removed CF_PROTECT_AGAINST_GRL flag as it is no longer
    necessary. New GRL implementation acquires protection
    against global read lock automagically when statement
    acquires metadata locks on tables or other objects it
    is going to change.
sql/sql_db.cc:
  Adjusted code to the fact that one now needs specify duration
  of lock when initializing MDL_request.
sql/sql_handler.cc:
  Removed call to broadcast_refresh() function. It is no longer
  needed with new GRL implementation.
  Adjusted code after introducing duration concept for metadata
  locks. Particularly to the fact transactional sentinel was
  replaced with explicit duration.
sql/sql_handler.h:
  Renamed mysql_ha_move_tickets_after_trans_sentinel() to
  mysql_ha_set_explicit_lock_duration() after transactional
  sentinel was obsoleted by locks with explicit duration.
sql/sql_insert.cc:
  Adjusted code handling delaying inserts after switching to
  new GRL implementation. Now connection thread initiating
  delayed insert has to acquire global IX lock in addition
  to metadata lock on table being inserted into. This IX lock
  protects against GRL and similarly to SW lock on table being
  inserted into has to be passed to handler thread in order to
  avoid deadlocks.
sql/sql_lex.cc:
  LEX::protect_against_global_read_lock member is no longer
  necessary since protection against GRL is automatically
  taken by code acquiring metadata locks/opening tables.
sql/sql_lex.h:
  LEX::protect_against_global_read_lock member is no longer
  necessary since protection against GRL is automatically
  taken by code acquiring metadata locks/opening tables.
sql/sql_parse.cc:
  - Implemented support for new approach to acquiring protection
    against global read lock. We no longer acquire such protection
    explicitly on the basis of statement flags. Instead we always
    rely on code which is responsible for acquiring metadata locks
    on object to be changed acquiring this protection. This is
    achieved by acquiring global IX metadata lock with statement
    duration. This lock is automatically released at the end of
    statement execution.
  - Changed implementation of CREATE/DROP PROCEDURE/FUNCTION not
    to release metadata locks and thus protection against of GRL
    in the middle of statement execution.
  - Adjusted code to the fact that one now needs specify duration
    of lock when initializing MDL_request and to the fact that
    savepoints for MDL subsystem are now represented by
    MDL_savepoint class.
sql/sql_prepare.cc:
  Adjusted code to the to the fact that savepoints for MDL
  subsystem are now represented by MDL_savepoint class.
sql/sql_rename.cc:
  With new GRL implementation there is no need to explicitly
  acquire protection against GRL before renaming tables.
  This happens automatically in code which acquires metadata
  locks on tables being renamed.
sql/sql_show.cc:
  Adjusted code to the fact that one now needs specify duration
  of lock when initializing MDL_request and to the fact that
  savepoints for MDL subsystem are now represented by
  MDL_savepoint class.
sql/sql_table.cc:
  - With new GRL implementation there is no need to explicitly
    acquire protection against GRL before dropping tables.
    This happens automatically in code which acquires metadata
    locks on tables being dropped.
  - Changed mysql_alter_table() not to release lock on new table
    name explicitly and to rely on automatic release of locks
    at the end of statement instead. This was necessary since
    now MDL_context::release_lock() is supported only for locks
    for explicit duration.
sql/sql_trigger.cc:
  With new GRL implementation there is no need to explicitly
  acquire protection against GRL before changing table triggers.
  This happens automatically in code which acquires metadata
  locks on tables which triggers are to be changed.
sql/sql_update.cc:
  Fix bug exposed by GRL testing. During prepare phase acquire
  only S metadata locks instead of SW locks to keep prepare of
  multi-UPDATE compatible with concurrent LOCK TABLES WRITE
  and global read lock.
sql/sql_view.cc:
  With new GRL implementation there is no need to explicitly
  acquire protection against GRL before creating view.
  This happens automatically in code which acquires metadata
  lock on view to be created.
sql/sql_yacc.yy:
  LEX::protect_against_global_read_lock member is no longer
  necessary since protection against GRL is automatically
  taken by code acquiring metadata locks/opening tables.
sql/table.cc:
  Adjusted code to the fact that one now needs specify duration
  of lock when initializing MDL_request.
sql/table.h:
  Adjusted code to the fact that one now needs specify duration
  of lock when initializing MDL_request.
sql/transaction.cc:
  Replaced custom implementation of global read lock with
  one based on metadata locks. Consequently when doing
  commit instead of calling method of Global_read_lock
  class to acquire protection against GRL we simply acquire
  IX in COMMIT namespace.
  Also adjusted code to the fact that MDL savepoint is now
  represented by MDL_savepoint class.

42 files changed, 988 insertions, 1096 deletions

diff --git a/sql/event_data_objects.cc b/sql/event_data_objects.cc
index 52c509621ac..bdc79dcbcfd 100644
--- a/sql/event_data_objects.cc
+++ b/sql/event_data_objects.cc
@@ -290,7 +290,6 @@ Event_basic::load_time_zone(THD *thd, const LEX_STRING tz_name)
 */
 
 Event_queue_element::Event_queue_element():
-  status_changed(FALSE), last_executed_changed(FALSE),
   on_completion(Event_parse_data::ON_COMPLETION_DROP),
   status(Event_parse_data::ENABLED), expression(0), dropped(FALSE),
   execution_count(0)
@@ -539,7 +538,6 @@ Event_queue_element::load_from_row(THD *thd, TABLE *table)
                                                    TIME_NO_ZERO_DATE);
     last_executed= my_tz_OFFSET0->TIME_to_gmt_sec(&time,&not_used);
   }
-  last_executed_changed= FALSE;
 
   if ((ptr= get_field(&mem_root, table->field[ET_FIELD_STATUS])) == NullS)
     DBUG_RETURN(TRUE);
@@ -935,7 +933,6 @@ Event_queue_element::compute_next_execution_time()
       DBUG_PRINT("info",("One-time event will be dropped: %d.", dropped));
 
       status= Event_parse_data::DISABLED;
-      status_changed= TRUE;
     }
     goto ret;
   }
@@ -955,7 +952,6 @@ Event_queue_element::compute_next_execution_time()
       dropped= TRUE;
     DBUG_PRINT("info", ("Dropped: %d", dropped));
     status= Event_parse_data::DISABLED;
-    status_changed= TRUE;
 
     goto ret;
   }
@@ -1018,7 +1014,6 @@ Event_queue_element::compute_next_execution_time()
         if (on_completion == Event_parse_data::ON_COMPLETION_DROP)
           dropped= TRUE;
         status= Event_parse_data::DISABLED;
-        status_changed= TRUE;
       }
       else
       {
@@ -1108,7 +1103,6 @@ Event_queue_element::compute_next_execution_time()
           execute_at= 0;
           execute_at_null= TRUE;
           status= Event_parse_data::DISABLED;
-          status_changed= TRUE;
           if (on_completion == Event_parse_data::ON_COMPLETION_DROP)
             dropped= TRUE;
         }
@@ -1144,50 +1138,11 @@ void
 Event_queue_element::mark_last_executed(THD *thd)
 {
   last_executed= (my_time_t) thd->query_start();
-  last_executed_changed= TRUE;
 
   execution_count++;
 }
 
 
-/*
-  Saves status and last_executed_at to the disk if changed.
-
-  SYNOPSIS
-    Event_queue_element::update_timing_fields()
-      thd - thread context
-
-  RETURN VALUE
-    FALSE   OK
-    TRUE    Error while opening mysql.event for writing or during
-            write on disk
-*/
-
-bool
-Event_queue_element::update_timing_fields(THD *thd)
-{
-  Event_db_repository *db_repository= Events::get_db_repository();
-  int ret;
-
-  DBUG_ENTER("Event_queue_element::update_timing_fields");
-
-  DBUG_PRINT("enter", ("name: %*s", (int) name.length, name.str));
-
-  /* No need to update if nothing has changed */
-  if (!(status_changed || last_executed_changed))
-    DBUG_RETURN(0);
-
-  ret= db_repository->update_timing_fields_for_event(thd,
-                                                     dbname, name,
-                                                     last_executed_changed,
-                                                     last_executed,
-                                                     status_changed,
-                                                     (ulonglong) status);
-  last_executed_changed= status_changed= FALSE;
-  DBUG_RETURN(ret);
-}
-
-
 static
 void
 append_datetime(String *buf, Time_zone *time_zone, my_time_t secs,
diff --git a/sql/event_data_objects.h b/sql/event_data_objects.h
index 9d17213bcb8..46740812d31 100644
--- a/sql/event_data_objects.h
+++ b/sql/event_data_objects.h
@@ -82,10 +82,6 @@ protected:
 
 class Event_queue_element : public Event_basic
 {
-protected:
-  bool status_changed;
-  bool last_executed_changed;
-
 public:
   int on_completion;
   int status;
@@ -117,9 +113,6 @@ public:
 
   void
   mark_last_executed(THD *thd);
-
-  bool
-  update_timing_fields(THD *thd);
 };
 
 
diff --git a/sql/event_db_repository.cc b/sql/event_db_repository.cc
index db508e4ea41..053558aa0c3 100644
--- a/sql/event_db_repository.cc
+++ b/sql/event_db_repository.cc
@@ -622,6 +622,12 @@ Event_db_repository::create_event(THD *thd, Event_parse_data *parse_data,
   TABLE *table= NULL;
   sp_head *sp= thd->lex->sphead;
   ulong saved_mode= thd->variables.sql_mode;
+  /*
+    Take a savepoint to release only the lock on mysql.event
+    table at the end but keep the global read lock and
+    possible other locks taken by the caller.
+  */
+  MDL_savepoint mdl_savepoint= thd->mdl_context.mdl_savepoint();
 
   DBUG_ENTER("Event_db_repository::create_event");
 
@@ -699,8 +705,8 @@ Event_db_repository::create_event(THD *thd, Event_parse_data *parse_data,
   ret= 0;
 
 end:
-  if (table)
-    close_mysql_tables(thd);
+  close_thread_tables(thd);
+  thd->mdl_context.rollback_to_savepoint(mdl_savepoint);
 
   thd->variables.sql_mode= saved_mode;
   DBUG_RETURN(test(ret));
@@ -734,6 +740,12 @@ Event_db_repository::update_event(THD *thd, Event_parse_data *parse_data,
   TABLE *table= NULL;
   sp_head *sp= thd->lex->sphead;
   ulong saved_mode= thd->variables.sql_mode;
+  /*
+    Take a savepoint to release only the lock on mysql.event
+    table at the end but keep the global read lock and
+    possible other locks taken by the caller.
+  */
+  MDL_savepoint mdl_savepoint= thd->mdl_context.mdl_savepoint();
   int ret= 1;
 
   DBUG_ENTER("Event_db_repository::update_event");
@@ -811,8 +823,8 @@ Event_db_repository::update_event(THD *thd, Event_parse_data *parse_data,
   ret= 0;
 
 end:
-  if (table)
-    close_mysql_tables(thd);
+  close_thread_tables(thd);
+  thd->mdl_context.rollback_to_savepoint(mdl_savepoint);
 
   thd->variables.sql_mode= saved_mode;
   DBUG_RETURN(test(ret));
@@ -838,6 +850,12 @@ Event_db_repository::drop_event(THD *thd, LEX_STRING db, LEX_STRING name,
                                 bool drop_if_exists)
 {
   TABLE *table= NULL;
+  /*
+    Take a savepoint to release only the lock on mysql.event
+    table at the end but keep the global read lock and
+    possible other locks taken by the caller.
+  */
+  MDL_savepoint mdl_savepoint= thd->mdl_context.mdl_savepoint();
   int ret= 1;
 
   DBUG_ENTER("Event_db_repository::drop_event");
@@ -866,8 +884,8 @@ Event_db_repository::drop_event(THD *thd, LEX_STRING db, LEX_STRING name,
   ret= 0;
 
 end:
-  if (table)
-    close_mysql_tables(thd);
+  close_thread_tables(thd);
+  thd->mdl_context.rollback_to_savepoint(mdl_savepoint);
 
   DBUG_RETURN(test(ret));
 }
@@ -940,7 +958,7 @@ Event_db_repository::drop_schema_events(THD *thd, LEX_STRING schema)
   TABLE *table= NULL;
   READ_RECORD read_record_info;
   enum enum_events_table_field field= ET_FIELD_DB;
-  MDL_ticket *mdl_savepoint= thd->mdl_context.mdl_savepoint();
+  MDL_savepoint mdl_savepoint= thd->mdl_context.mdl_savepoint();
   DBUG_ENTER("Event_db_repository::drop_schema_events");
   DBUG_PRINT("enter", ("field=%d schema=%s", field, schema.str));
 
@@ -1042,15 +1060,14 @@ Event_db_repository::
 update_timing_fields_for_event(THD *thd,
                                LEX_STRING event_db_name,
                                LEX_STRING event_name,
-                               bool update_last_executed,
                                my_time_t last_executed,
-                               bool update_status,
                                ulonglong status)
 {
   TABLE *table= NULL;
   Field **fields;
   int ret= 1;
   bool save_binlog_row_based;
+  MYSQL_TIME time;
 
   DBUG_ENTER("Event_db_repository::update_timing_fields_for_event");
 
@@ -1075,20 +1092,12 @@ update_timing_fields_for_event(THD *thd,
   /* Don't update create on row update. */
   table->timestamp_field_type= TIMESTAMP_NO_AUTO_SET;
 
-  if (update_last_executed)
-  {
-    MYSQL_TIME time;
-    my_tz_OFFSET0->gmt_sec_to_TIME(&time, last_executed);
+  my_tz_OFFSET0->gmt_sec_to_TIME(&time, last_executed);
+  fields[ET_FIELD_LAST_EXECUTED]->set_notnull();
+  fields[ET_FIELD_LAST_EXECUTED]->store_time(&time, MYSQL_TIMESTAMP_DATETIME);
 
-    fields[ET_FIELD_LAST_EXECUTED]->set_notnull();
-    fields[ET_FIELD_LAST_EXECUTED]->store_time(&time,
-                                               MYSQL_TIMESTAMP_DATETIME);
-  }
-  if (update_status)
-  {
-    fields[ET_FIELD_STATUS]->set_notnull();
-    fields[ET_FIELD_STATUS]->store(status, TRUE);
-  }
+  fields[ET_FIELD_STATUS]->set_notnull();
+  fields[ET_FIELD_STATUS]->store(status, TRUE);
 
   if ((ret= table->file->ha_update_row(table->record[1], table->record[0])))
   {
diff --git a/sql/event_db_repository.h b/sql/event_db_repository.h
index ea7f3bbac0e..58484d17f06 100644
--- a/sql/event_db_repository.h
+++ b/sql/event_db_repository.h
@@ -101,9 +101,7 @@ public:
   update_timing_fields_for_event(THD *thd,
                                  LEX_STRING event_db_name,
                                  LEX_STRING event_name,
-                                 bool update_last_executed,
                                  my_time_t last_executed,
-                                 bool update_status,
                                  ulonglong status);
 public:
   static bool
diff --git a/sql/event_queue.cc b/sql/event_queue.cc
index 458a7c1defd..92b8a2c9071 100644
--- a/sql/event_queue.cc
+++ b/sql/event_queue.cc
@@ -17,6 +17,8 @@
 #include "unireg.h"
 #include "event_queue.h"
 #include "event_data_objects.h"
+#include "event_db_repository.h"
+#include "events.h"
 #include "sql_audit.h"
 #include "tztime.h"     // my_tz_find, my_tz_OFFSET0, struct Time_zone
 #include "log.h"        // sql_print_error
@@ -444,7 +446,6 @@ Event_queue::recalculate_activation_times(THD *thd)
   for (i= 0; i < queue.elements; i++)
   {
     ((Event_queue_element*)queue_element(&queue, i))->compute_next_execution_time();
-    ((Event_queue_element*)queue_element(&queue, i))->update_timing_fields(thd);
   }
   queue_fix(&queue);
   /*
@@ -567,6 +568,8 @@ Event_queue::get_top_for_execution_if_time(THD *thd,
 {
   bool ret= FALSE;
   *event_name= NULL;
+  my_time_t last_executed;
+  int status;
   DBUG_ENTER("Event_queue::get_top_for_execution_if_time");
 
   LOCK_QUEUE_DATA();
@@ -632,8 +635,14 @@ Event_queue::get_top_for_execution_if_time(THD *thd,
 
     top->execution_count++;
     (*event_name)->dropped= top->dropped;
+    /*
+      Save new values of last_executed timestamp and event status on stack
+      in order to be able to update event description in system table once
+      QUEUE_DATA lock is released.
+    */
+    last_executed= top->last_executed;
+    status= top->status;
 
-    top->update_timing_fields(thd);
     if (top->status == Event_parse_data::DISABLED)
     {
       DBUG_PRINT("info", ("removing from the queue"));
@@ -656,9 +665,16 @@ end:
                       ret, (long) *event_name));
 
   if (*event_name)
+  {
     DBUG_PRINT("info", ("db: %s  name: %s",
                         (*event_name)->dbname.str, (*event_name)->name.str));
 
+    Event_db_repository *db_repository= Events::get_db_repository();
+    (void) db_repository->update_timing_fields_for_event(thd,
+                            (*event_name)->dbname, (*event_name)->name,
+                            last_executed, (ulonglong) status);
+  }
+
   DBUG_RETURN(ret);
 }
 
diff --git a/sql/events.cc b/sql/events.cc
index e7e47801586..23a0dc9eb52 100644
--- a/sql/events.cc
+++ b/sql/events.cc
@@ -30,6 +30,7 @@
 #include "event_scheduler.h"
 #include "sp_head.h" // for Stored_program_creation_ctx
 #include "set_var.h"
+#include "lock.h"   // lock_object_name
 
 /**
   @addtogroup Event_Scheduler
@@ -77,7 +78,6 @@ Event_queue *Events::event_queue;
 Event_scheduler *Events::scheduler;
 Event_db_repository *Events::db_repository;
 ulong Events::opt_event_scheduler= Events::EVENTS_OFF;
-mysql_mutex_t Events::LOCK_event_metadata;
 bool Events::check_system_tables_error= FALSE;
 
 
@@ -340,7 +340,9 @@ Events::create_event(THD *thd, Event_parse_data *parse_data,
   if ((save_binlog_row_based= thd->is_current_stmt_binlog_format_row()))
     thd->clear_current_stmt_binlog_format_row();
 
-  mysql_mutex_lock(&LOCK_event_metadata);
+  if (lock_object_name(thd, MDL_key::EVENT,
+                       parse_data->dbname.str, parse_data->name.str))
+    DBUG_RETURN(TRUE);
 
   /* On error conditions my_error() is called so no need to handle here */
   if (!(ret= db_repository->create_event(thd, parse_data, if_not_exists)))
@@ -388,7 +390,6 @@ Events::create_event(THD *thd, Event_parse_data *parse_data,
       }
     }
   }
-  mysql_mutex_unlock(&LOCK_event_metadata);
   /* Restore the state of binlog format */
   DBUG_ASSERT(!thd->is_current_stmt_binlog_format_row());
   if (save_binlog_row_based)
@@ -472,7 +473,9 @@ Events::update_event(THD *thd, Event_parse_data *parse_data,
   if ((save_binlog_row_based= thd->is_current_stmt_binlog_format_row()))
     thd->clear_current_stmt_binlog_format_row();
 
-  mysql_mutex_lock(&LOCK_event_metadata);
+  if (lock_object_name(thd, MDL_key::EVENT,
+                       parse_data->dbname.str, parse_data->name.str))
+    DBUG_RETURN(TRUE);
 
   /* On error conditions my_error() is called so no need to handle here */
   if (!(ret= db_repository->update_event(thd, parse_data,
@@ -502,7 +505,6 @@ Events::update_event(THD *thd, Event_parse_data *parse_data,
       ret= write_bin_log(thd, TRUE, thd->query(), thd->query_length());
     }
   }
-  mysql_mutex_unlock(&LOCK_event_metadata);
   /* Restore the state of binlog format */
   DBUG_ASSERT(!thd->is_current_stmt_binlog_format_row());
   if (save_binlog_row_based)
@@ -556,7 +558,9 @@ Events::drop_event(THD *thd, LEX_STRING dbname, LEX_STRING name, bool if_exists)
   if ((save_binlog_row_based= thd->is_current_stmt_binlog_format_row()))
     thd->clear_current_stmt_binlog_format_row();
 
-  mysql_mutex_lock(&LOCK_event_metadata);
+  if (lock_object_name(thd, MDL_key::EVENT,
+                       dbname.str, name.str))
+    DBUG_RETURN(TRUE);
   /* On error conditions my_error() is called so no need to handle here */
   if (!(ret= db_repository->drop_event(thd, dbname, name, if_exists)))
   {
@@ -566,7 +570,6 @@ Events::drop_event(THD *thd, LEX_STRING dbname, LEX_STRING name, bool if_exists)
     DBUG_ASSERT(thd->query() && thd->query_length());
     ret= write_bin_log(thd, TRUE, thd->query(), thd->query_length());
   }
-  mysql_mutex_unlock(&LOCK_event_metadata);
   /* Restore the state of binlog format */
   DBUG_ASSERT(!thd->is_current_stmt_binlog_format_row());
   if (save_binlog_row_based)
@@ -595,15 +598,12 @@ Events::drop_schema_events(THD *thd, char *db)
   DBUG_PRINT("enter", ("dropping events from %s", db));
 
   /*
-    sic: no check if the scheduler is disabled or system tables
+    Sic: no check if the scheduler is disabled or system tables
     are damaged, as intended.
   */
-
-  mysql_mutex_lock(&LOCK_event_metadata);
   if (event_queue)
     event_queue->drop_schema_events(thd, db_lex);
   db_repository->drop_schema_events(thd, db_lex);
-  mysql_mutex_unlock(&LOCK_event_metadata);
 
   DBUG_VOID_RETURN;
 }
@@ -915,12 +915,11 @@ Events::deinit()
 }
 
 #ifdef HAVE_PSI_INTERFACE
-PSI_mutex_key key_LOCK_event_metadata, key_LOCK_event_queue,
+PSI_mutex_key key_LOCK_event_queue,
               key_event_scheduler_LOCK_scheduler_state;
 
 static PSI_mutex_info all_events_mutexes[]=
 {
-  { &key_LOCK_event_metadata, "LOCK_event_metadata", PSI_FLAG_GLOBAL},
   { &key_LOCK_event_queue, "LOCK_event_queue", PSI_FLAG_GLOBAL},
   { &key_event_scheduler_LOCK_scheduler_state, "Event_scheduler::LOCK_scheduler_state", PSI_FLAG_GLOBAL}
 };
@@ -974,23 +973,6 @@ Events::init_mutexes()
 #ifdef HAVE_PSI_INTERFACE
   init_events_psi_keys();
 #endif
-
-  mysql_mutex_init(key_LOCK_event_metadata,
-                   &LOCK_event_metadata, MY_MUTEX_INIT_FAST);
-}
-
-
-/*
-  Destroys Events mutexes
-
-  SYNOPSIS
-    Events::destroy_mutexes()
-*/
-
-void
-Events::destroy_mutexes()
-{
-  mysql_mutex_destroy(&LOCK_event_metadata);
 }
 
 
diff --git a/sql/events.h b/sql/events.h
index f3ebc6da4ad..a337b29049a 100644
--- a/sql/events.h
+++ b/sql/events.h
@@ -26,8 +26,7 @@
 */
 
 #ifdef HAVE_PSI_INTERFACE
-extern PSI_mutex_key key_LOCK_event_metadata,
-                     key_event_scheduler_LOCK_scheduler_state;
+extern PSI_mutex_key key_event_scheduler_LOCK_scheduler_state;
 extern PSI_cond_key key_event_scheduler_COND_state;
 extern PSI_thread_key key_thread_event_scheduler, key_thread_event_worker;
 #endif /* HAVE_PSI_INTERFACE */
@@ -79,7 +78,6 @@ public:
   enum enum_opt_event_scheduler { EVENTS_OFF, EVENTS_ON, EVENTS_DISABLED };
   /* Protected using LOCK_global_system_variables only. */
   static ulong opt_event_scheduler;
-  static mysql_mutex_t LOCK_event_metadata;
   static bool check_if_system_tables_error();
   static bool start();
   static bool stop();
diff --git a/sql/ha_ndbcluster.cc b/sql/ha_ndbcluster.cc
index 6b07cf76d79..20745db9ce9 100644
--- a/sql/ha_ndbcluster.cc
+++ b/sql/ha_ndbcluster.cc
@@ -7382,38 +7382,35 @@ int ndbcluster_find_files(handlerton *hton, THD *thd,
   }
 
   /*
+    Delete old files.
+
     ndbcluster_find_files() may be called from I_S code and ndbcluster_binlog
     thread in situations when some tables are already open. This means that
     code below will try to obtain exclusive metadata lock on some table
-    while holding shared meta-data lock on other tables. This might lead to
-    a deadlock, and therefore is disallowed by assertions of the metadata
-    locking subsystem. This is violation of metadata
-    locking protocol which has to be closed ASAP.
+    while holding shared meta-data lock on other tables. This might lead to a
+    deadlock but such a deadlock should be detected by MDL deadlock detector.
+
     XXX: the scenario described above is not covered with any test.
   */
-  if (!global_read_lock)
-  {
-    // Delete old files
-    List_iterator_fast<char> it3(delete_list);
-    while ((file_name_str= it3++))
-    {
-      DBUG_PRINT("info", ("Remove table %s/%s", db, file_name_str));
-      // Delete the table and all related files
-      TABLE_LIST table_list;
-      table_list.init_one_table(db, strlen(db), file_name_str,
-                                strlen(file_name_str), file_name_str,
-                                TL_WRITE);
-      table_list.mdl_request.set_type(MDL_EXCLUSIVE);
-      (void)mysql_rm_table_part2(thd, &table_list,
-                                 FALSE,   /* if_exists */
-                                 FALSE,   /* drop_temporary */ 
-                                 FALSE,   /* drop_view */
-                                 TRUE     /* dont_log_query*/);
-      trans_commit_implicit(thd); /* Safety, should be unnecessary. */
-      thd->mdl_context.release_transactional_locks();
-      /* Clear error message that is returned when table is deleted */
-      thd->clear_error();
-    }
+  List_iterator_fast<char> it3(delete_list);
+  while ((file_name_str= it3++))
+  {
+    DBUG_PRINT("info", ("Remove table %s/%s", db, file_name_str));
+    /* Delete the table and all related files. */
+    TABLE_LIST table_list;
+    table_list.init_one_table(db, strlen(db), file_name_str,
+                              strlen(file_name_str), file_name_str,
+                              TL_WRITE);
+    table_list.mdl_request.set_type(MDL_EXCLUSIVE);
+    (void)mysql_rm_table_part2(thd, &table_list,
+                               FALSE,   /* if_exists */
+                               FALSE,   /* drop_temporary */
+                               FALSE,   /* drop_view */
+                               TRUE     /* dont_log_query*/);
+    trans_commit_implicit(thd); /* Safety, should be unnecessary. */
+    thd->mdl_context.release_transactional_locks();
+    /* Clear error message that is returned when table is deleted */
+    thd->clear_error();
   }
 
   /* Lock mutex before creating .FRM files. */
diff --git a/sql/handler.cc b/sql/handler.cc
index eb060002f48..22bb3069a9f 100644
--- a/sql/handler.cc
+++ b/sql/handler.cc
@@ -29,8 +29,6 @@
 #include "sql_cache.h"                   // query_cache, query_cache_*
 #include "key.h"     // key_copy, key_unpack, key_cmp_if_same, key_cmp
 #include "sql_table.h"                   // build_table_filename
-#include "lock.h"               // wait_if_global_read_lock,
-                                // start_waiting_global_read_lock
 #include "sql_parse.h"                          // check_stack_overrun
 #include "sql_acl.h"            // SUPER_ACL
 #include "sql_base.h"           // free_io_cache
@@ -41,6 +39,7 @@
 #include "transaction.h"
 #include <errno.h>
 #include "probes_mysql.h"
+#include "debug_sync.h"         // DEBUG_SYNC
 
 #ifdef WITH_PARTITION_STORAGE_ENGINE
 #include "ha_partition.h"
@@ -1155,6 +1154,7 @@ int ha_commit_trans(THD *thd, bool all)
   {
     uint rw_ha_count;
     bool rw_trans;
+    MDL_request mdl_request;
 
     DBUG_EXECUTE_IF("crash_commit_before", DBUG_SUICIDE(););
 
@@ -1166,11 +1166,27 @@ int ha_commit_trans(THD *thd, bool all)
     /* rw_trans is TRUE when we in a transaction changing data */
     rw_trans= is_real_trans && (rw_ha_count > 0);
 
-    if (rw_trans &&
-        thd->global_read_lock.wait_if_global_read_lock(thd, FALSE, FALSE))
+    if (rw_trans)
     {
-      ha_rollback_trans(thd, all);
-      DBUG_RETURN(1);
+      /*
+        Acquire a metadata lock which will ensure that COMMIT is blocked
+        by an active FLUSH TABLES WITH READ LOCK (and vice versa:
+        COMMIT in progress blocks FTWRL).
+
+        We allow the owner of FTWRL to COMMIT; we assume that it knows
+        what it does.
+      */
+      mdl_request.init(MDL_key::COMMIT, "", "", MDL_INTENTION_EXCLUSIVE,
+                       MDL_EXPLICIT);
+
+      if (thd->mdl_context.acquire_lock(&mdl_request,
+                                        thd->variables.lock_wait_timeout))
+      {
+        ha_rollback_trans(thd, all);
+        DBUG_RETURN(1);
+      }
+
+      DEBUG_SYNC(thd, "ha_commit_trans_after_acquire_commit_lock");
     }
 
     if (rw_trans &&
@@ -1225,8 +1241,16 @@ int ha_commit_trans(THD *thd, bool all)
     DBUG_EXECUTE_IF("crash_commit_after", DBUG_SUICIDE(););
     RUN_HOOK(transaction, after_commit, (thd, FALSE));
 end:
-    if (rw_trans)
-      thd->global_read_lock.start_waiting_global_read_lock(thd);
+    if (rw_trans && mdl_request.ticket)
+    {
+      /*
+        We do not always immediately release transactional locks
+        after ha_commit_trans() (see uses of ha_enable_transaction()),
+        thus we release the commit blocker lock as soon as it's
+        not needed.
+      */
+      thd->mdl_context.release_lock(mdl_request.ticket);
+    }
   }
   /* Free resources and perform other cleanup even for 'empty' transactions. */
   else if (is_real_trans)
diff --git a/sql/lock.cc b/sql/lock.cc
index 84cc24b3f61..2e141e1c9fb 100644
--- a/sql/lock.cc
+++ b/sql/lock.cc
@@ -777,8 +777,11 @@ bool lock_schema_name(THD *thd, const char *db)
     return TRUE;
   }
 
-  global_request.init(MDL_key::GLOBAL, "", "", MDL_INTENTION_EXCLUSIVE);
-  mdl_request.init(MDL_key::SCHEMA, db, "", MDL_EXCLUSIVE);
+  if (thd->global_read_lock.can_acquire_protection())
+    return TRUE;
+  global_request.init(MDL_key::GLOBAL, "", "", MDL_INTENTION_EXCLUSIVE,
+                      MDL_STATEMENT);
+  mdl_request.init(MDL_key::SCHEMA, db, "", MDL_EXCLUSIVE, MDL_TRANSACTION);
 
   mdl_requests.push_front(&mdl_request);
   mdl_requests.push_front(&global_request);
@@ -793,13 +796,13 @@ bool lock_schema_name(THD *thd, const char *db)
 
 
 /**
-  Obtain an exclusive metadata lock on the stored routine name.
+  Obtain an exclusive metadata lock on an object name.
 
   @param thd         Thread handle.
-  @param is_function Stored routine type (only functions or procedures
-                     are name-locked.
-  @param db          The schema the routine belongs to.
-  @param name        Routine name.
+  @param mdl_type    Object type (currently functions, procedures
+                     and events can be name-locked).
+  @param db          The schema the object belongs to.
+  @param name        Object name in the schema.
 
   This function assumes that no metadata locks were acquired
   before calling it. Additionally, it cannot be called while
@@ -815,12 +818,9 @@ bool lock_schema_name(THD *thd, const char *db)
                  or this connection was killed.
 */
 
-bool lock_routine_name(THD *thd, bool is_function,
+bool lock_object_name(THD *thd, MDL_key::enum_mdl_namespace mdl_type,
                        const char *db, const char *name)
 {
-  MDL_key::enum_mdl_namespace mdl_type= (is_function ?
-                                         MDL_key::FUNCTION :
-                                         MDL_key::PROCEDURE);
   MDL_request_list mdl_requests;
   MDL_request global_request;
   MDL_request schema_request;
@@ -836,9 +836,13 @@ bool lock_routine_name(THD *thd, bool is_function,
   DBUG_ASSERT(name);
   DEBUG_SYNC(thd, "before_wait_locked_pname");
 
-  global_request.init(MDL_key::GLOBAL, "", "", MDL_INTENTION_EXCLUSIVE);
-  schema_request.init(MDL_key::SCHEMA, db, "", MDL_INTENTION_EXCLUSIVE);
-  mdl_request.init(mdl_type, db, name, MDL_EXCLUSIVE);
+  if (thd->global_read_lock.can_acquire_protection())
+    return TRUE;
+  global_request.init(MDL_key::GLOBAL, "", "", MDL_INTENTION_EXCLUSIVE,
+                      MDL_STATEMENT);
+  schema_request.init(MDL_key::SCHEMA, db, "", MDL_INTENTION_EXCLUSIVE,
+                      MDL_TRANSACTION);
+  mdl_request.init(mdl_type, db, name, MDL_EXCLUSIVE, MDL_TRANSACTION);
 
   mdl_requests.push_front(&mdl_request);
   mdl_requests.push_front(&schema_request);
@@ -888,45 +892,24 @@ static void print_lock_error(int error, const char *table)
 /****************************************************************************
   Handling of global read locks
 
+  Global read lock is implemented using metadata lock infrastructure.
+
   Taking the global read lock is TWO steps (2nd step is optional; without
   it, COMMIT of existing transactions will be allowed):
   lock_global_read_lock() THEN make_global_read_lock_block_commit().
 
-  The global locks are handled through the global variables:
-  global_read_lock
-    count of threads which have the global read lock (i.e. have completed at
-    least the first step above)
-  global_read_lock_blocks_commit
-    count of threads which have the global read lock and block
-    commits (i.e. are in or have completed the second step above)
-  waiting_for_read_lock
-    count of threads which want to take a global read lock but cannot
-  protect_against_global_read_lock
-    count of threads which have set protection against global read lock.
-
-  access to them is protected with a mutex LOCK_global_read_lock
-
-  (XXX: one should never take LOCK_open if LOCK_global_read_lock is
-  taken, otherwise a deadlock may occur. Other mutexes could be a
-  problem too - grep the code for global_read_lock if you want to use
-  any other mutex here) Also one must not hold LOCK_open when calling
-  wait_if_global_read_lock(). When the thread with the global read lock
-  tries to close its tables, it needs to take LOCK_open in
-  close_thread_table().
-
   How blocking of threads by global read lock is achieved: that's
-  advisory. Any piece of code which should be blocked by global read lock must
-  be designed like this:
-  - call to wait_if_global_read_lock(). When this returns 0, no global read
-  lock is owned; if argument abort_on_refresh was 0, none can be obtained.
-  - job
-  - if abort_on_refresh was 0, call to start_waiting_global_read_lock() to
-  allow other threads to get the global read lock. I.e. removal of the
-  protection.
-  (Note: it's a bit like an implementation of rwlock).
-
-  [ I am sorry to mention some SQL syntaxes below I know I shouldn't but found
-  no better descriptive way ]
+  semi-automatic. We assume that any statement which should be blocked
+  by global read lock will either open and acquires write-lock on tables
+  or acquires metadata locks on objects it is going to modify. For any
+  such statement global IX metadata lock is automatically acquired for
+  its duration (in case of LOCK TABLES until end of LOCK TABLES mode).
+  And lock_global_read_lock() simply acquires global S metadata lock
+  and thus prohibits execution of statements which modify data (unless
+  they modify only temporary tables). If deadlock happens it is detected
+  by MDL subsystem and resolved in the standard fashion (by backing-off
+  metadata locks acquired so far and restarting open tables process
+  if possible).
 
   Why does FLUSH TABLES WITH READ LOCK need to block COMMIT: because it's used
   to read a non-moving SHOW MASTER STATUS, and a COMMIT writes to the binary
@@ -960,11 +943,6 @@ static void print_lock_error(int error, const char *table)
 
 ****************************************************************************/
 
-volatile uint global_read_lock=0;
-volatile uint global_read_lock_blocks_commit=0;
-static volatile uint protect_against_global_read_lock=0;
-static volatile uint waiting_for_read_lock=0;
-
 /**
   Take global read lock, wait if there is protection against lock.
 
@@ -985,84 +963,17 @@ bool Global_read_lock::lock_global_read_lock(THD *thd)
   if (!m_state)
   {
     MDL_request mdl_request;
-    const char *old_message;
-    const char *new_message= "Waiting to get readlock";
-    (void) mysql_mutex_lock(&LOCK_global_read_lock);
-
-    old_message= thd->enter_cond(&COND_global_read_lock,
-                                 &LOCK_global_read_lock, new_message);
-    DBUG_PRINT("info",
-               ("waiting_for: %d  protect_against: %d",
-                waiting_for_read_lock, protect_against_global_read_lock));
-
-    waiting_for_read_lock++;
-
-#if defined(ENABLED_DEBUG_SYNC)
-    /*
-      The below sync point fires if we have to wait for
-      protect_against_global_read_lock.
-
-      WARNING: Beware to use WAIT_FOR with this sync point. We hold
-      LOCK_global_read_lock here.
-
-      The sync point is after enter_cond() so that proc_info is
-      available immediately after the sync point sends a SIGNAL. This
-      can make tests more reliable.
-
-      The sync point is before the loop so that it is executed only once.
-    */
-    if (protect_against_global_read_lock && !thd->killed)
-    {
-      DEBUG_SYNC(thd, "wait_lock_global_read_lock");
-    }
-#endif /* defined(ENABLED_DEBUG_SYNC) */
-
-    while (protect_against_global_read_lock && !thd->killed)
-      mysql_cond_wait(&COND_global_read_lock, &LOCK_global_read_lock);
-    waiting_for_read_lock--;
-    if (thd->killed)
-    {
-      thd->exit_cond(old_message);
-      DBUG_RETURN(1);
-    }
-    m_state= GRL_ACQUIRED;
-    global_read_lock++;
-    thd->exit_cond(old_message); // this unlocks LOCK_global_read_lock
-    /*
-      When we perform FLUSH TABLES or ALTER TABLE under LOCK TABLES,
-      tables being reopened are protected only by meta-data locks at
-      some point. To avoid sneaking in with our global read lock at
-      this moment we have to take global shared meta data lock.
-
-      TODO: We should change this code to acquire global shared metadata
-            lock before acquiring global read lock. But in order to do
-            this we have to get rid of all those places in which
-            wait_if_global_read_lock() is called before acquiring
-            metadata locks first. Also long-term we should get rid of
-            redundancy between metadata locks, global read lock and DDL
-            blocker (see WL#4399 and WL#4400).
-    */
 
     DBUG_ASSERT(! thd->mdl_context.is_lock_owner(MDL_key::GLOBAL, "", "",
                                                  MDL_SHARED));
-    mdl_request.init(MDL_key::GLOBAL, "", "", MDL_SHARED);
+    mdl_request.init(MDL_key::GLOBAL, "", "", MDL_SHARED, MDL_EXPLICIT);
 
     if (thd->mdl_context.acquire_lock(&mdl_request,
                                       thd->variables.lock_wait_timeout))
-    {
-      /* Our thread was killed -- return back to initial state. */
-      mysql_mutex_lock(&LOCK_global_read_lock);
-      if (!(--global_read_lock))
-      {
-        DBUG_PRINT("signal", ("Broadcasting COND_global_read_lock"));
-        mysql_cond_broadcast(&COND_global_read_lock);
-      }
-      mysql_mutex_unlock(&LOCK_global_read_lock);
-      m_state= GRL_NONE;
       DBUG_RETURN(1);
-    }
-    thd->mdl_context.move_ticket_after_trans_sentinel(mdl_request.ticket);
+
     m_mdl_global_shared_lock= mdl_request.ticket;
+    m_state= GRL_ACQUIRED;
   }
   /*
     We DON'T set global_read_lock_blocks_commit now, it will be set after
@@ -1088,166 +999,22 @@ bool Global_read_lock::lock_global_read_lock(THD *thd)
 
 void Global_read_lock::unlock_global_read_lock(THD *thd)
 {
-  uint tmp;
   DBUG_ENTER("unlock_global_read_lock");
-  DBUG_PRINT("info",
-             ("global_read_lock: %u  global_read_lock_blocks_commit: %u",
-              global_read_lock, global_read_lock_blocks_commit));
 
   DBUG_ASSERT(m_mdl_global_shared_lock && m_state);
 
-  thd->mdl_context.release_lock(m_mdl_global_shared_lock);
-  m_mdl_global_shared_lock= NULL;
-
-  mysql_mutex_lock(&LOCK_global_read_lock);
-  tmp= --global_read_lock;
-  if (m_state == GRL_ACQUIRED_AND_BLOCKS_COMMIT)
-    --global_read_lock_blocks_commit;
-  mysql_mutex_unlock(&LOCK_global_read_lock);
-  /* Send the signal outside the mutex to avoid a context switch */
-  if (!tmp)
+  if (m_mdl_blocks_commits_lock)
   {
-    DBUG_PRINT("signal", ("Broadcasting COND_global_read_lock"));
-    mysql_cond_broadcast(&COND_global_read_lock);
+    thd->mdl_context.release_lock(m_mdl_blocks_commits_lock);
+    m_mdl_blocks_commits_lock= NULL;
   }
+  thd->mdl_context.release_lock(m_mdl_global_shared_lock);
+  m_mdl_global_shared_lock= NULL;
   m_state= GRL_NONE;
 
   DBUG_VOID_RETURN;
 }
 
-/**
-  Wait if the global read lock is set, and optionally seek protection against
-  global read lock.
-
-  See also "Handling of global read locks" above.
-
-  @param thd              Reference to thread.
-  @param abort_on_refresh If True, abort waiting if a refresh occurs,
-                          do NOT seek protection against GRL.
-                          If False, wait until the GRL is released and seek
-                          protection against GRL.
-  @param is_not_commit    If False, called from a commit operation,
-                          wait only if commit blocking is also enabled.
-
-  @retval False  Success, protection against global read lock is set
-                          (if !abort_on_refresh)
-  @retval True   Failure, wait was aborted or thread was killed.
-*/
-
-#define must_wait (global_read_lock &&                             \
-                   (is_not_commit ||                               \
-                    global_read_lock_blocks_commit))
-
-bool Global_read_lock::
-wait_if_global_read_lock(THD *thd, bool abort_on_refresh,
-                         bool is_not_commit)
-{
-  const char *UNINIT_VAR(old_message);
-  bool result= 0, need_exit_cond;
-  DBUG_ENTER("wait_if_global_read_lock");
-
-  /*
-    If we already have protection against global read lock,
-    just increment the counter.
-  */
-  if (unlikely(m_protection_count > 0))
-  {
-    if (!abort_on_refresh)
-      m_protection_count++;
-    DBUG_RETURN(FALSE);
-  }
-  /*
-    Assert that we do not own LOCK_open. If we would own it, other
-    threads could not close their tables. This would make a pretty
-    deadlock.
-  */
-  mysql_mutex_assert_not_owner(&LOCK_open);
-
-  mysql_mutex_lock(&LOCK_global_read_lock);
-  if ((need_exit_cond= must_wait))
-  {
-    if (m_state)		// This thread had the read locks
-    {
-      if (is_not_commit)
-        my_message(ER_CANT_UPDATE_WITH_READLOCK,
-                   ER(ER_CANT_UPDATE_WITH_READLOCK), MYF(0));
-      mysql_mutex_unlock(&LOCK_global_read_lock);
-      /*
-        We allow FLUSHer to COMMIT; we assume FLUSHer knows what it does.
-        This allowance is needed to not break existing versions of innobackup
-        which do a BEGIN; INSERT; FLUSH TABLES WITH READ LOCK; COMMIT.
-      */
-      DBUG_RETURN(is_not_commit);
-    }
-    old_message=thd->enter_cond(&COND_global_read_lock, &LOCK_global_read_lock,
-				"Waiting for release of readlock");
-    while (must_wait && ! thd->killed &&
-	   (!abort_on_refresh || !thd->open_tables ||
-            thd->open_tables->s->version == refresh_version))
-    {
-      DBUG_PRINT("signal", ("Waiting for COND_global_read_lock"));
-      mysql_cond_wait(&COND_global_read_lock, &LOCK_global_read_lock);
-      DBUG_PRINT("signal", ("Got COND_global_read_lock"));
-    }
-    if (thd->killed)
-      result=1;
-  }
-  if (!abort_on_refresh && !result)
-  {
-    m_protection_count++;
-    protect_against_global_read_lock++;
-    DBUG_PRINT("sql_lock", ("protect_against_global_read_lock incr: %u",
-                            protect_against_global_read_lock));
-  }
-  /*
-    The following is only true in case of a global read locks (which is rare)
-    and if old_message is set
-  */
-  if (unlikely(need_exit_cond))
-    thd->exit_cond(old_message); // this unlocks LOCK_global_read_lock
-  else
-    mysql_mutex_unlock(&LOCK_global_read_lock);
-  DBUG_RETURN(result);
-}
-
-
-/**
-  Release protection against global read lock and restart
-  global read lock waiters.
-
-  Should only be called if we have protection against global read lock.
-
-  See also "Handling of global read locks" above.
-
-  @param thd     Reference to thread.
-*/
-
-void Global_read_lock::start_waiting_global_read_lock(THD *thd)
-{
-  bool tmp;
-  DBUG_ENTER("start_waiting_global_read_lock");
-  /*
-    Ignore request if we do not have protection against global read lock.
-    (Note that this is a violation of the interface contract, hence the assert).
-  */
-  DBUG_ASSERT(m_protection_count > 0);
-  if (unlikely(m_protection_count == 0))
-    DBUG_VOID_RETURN;
-  /* Decrement local read lock protection counter, return if we still have it */
-  if (unlikely(--m_protection_count > 0))
-    DBUG_VOID_RETURN;
-  if (unlikely(m_state))
-    DBUG_VOID_RETURN;
-  mysql_mutex_lock(&LOCK_global_read_lock);
-  DBUG_ASSERT(protect_against_global_read_lock);
-  tmp= (!--protect_against_global_read_lock &&
-        (waiting_for_read_lock || global_read_lock_blocks_commit));
-  mysql_mutex_unlock(&LOCK_global_read_lock);
-  if (tmp)
-    mysql_cond_broadcast(&COND_global_read_lock);
-  DBUG_VOID_RETURN;
-}
-
 
 /**
   Make global read lock also block commits.
@@ -1266,8 +1033,7 @@ void Global_read_lock::start_waiting_global_read_lock(THD *thd)
 
 bool Global_read_lock::make_global_read_lock_block_commit(THD *thd)
 {
-  bool error;
-  const char *old_message;
+  MDL_request mdl_request;
   DBUG_ENTER("make_global_read_lock_block_commit");
   /*
     If we didn't succeed lock_global_read_lock(), or if we already suceeded
@@ -1275,42 +1041,32 @@ bool Global_read_lock::make_global_read_lock_block_commit(THD *thd)
   */
   if (m_state != GRL_ACQUIRED)
     DBUG_RETURN(0);
-  mysql_mutex_lock(&LOCK_global_read_lock);
-  /* increment this BEFORE waiting on cond (otherwise race cond) */
-  global_read_lock_blocks_commit++;
-  /* For testing we set up some blocking, to see if we can be killed */
-  DBUG_EXECUTE_IF("make_global_read_lock_block_commit_loop",
-                  protect_against_global_read_lock++;);
-  old_message= thd->enter_cond(&COND_global_read_lock, &LOCK_global_read_lock,
-                               "Waiting for all running commits to finish");
-  while (protect_against_global_read_lock && !thd->killed)
-    mysql_cond_wait(&COND_global_read_lock, &LOCK_global_read_lock);
-  DBUG_EXECUTE_IF("make_global_read_lock_block_commit_loop",
-                  protect_against_global_read_lock--;);
-  if ((error= test(thd->killed)))
-    global_read_lock_blocks_commit--; // undo what we did
-  else
-    m_state= GRL_ACQUIRED_AND_BLOCKS_COMMIT;
-  thd->exit_cond(old_message); // this unlocks LOCK_global_read_lock
-  DBUG_RETURN(error);
+
+  mdl_request.init(MDL_key::COMMIT, "", "", MDL_SHARED, MDL_EXPLICIT);
+
+  if (thd->mdl_context.acquire_lock(&mdl_request,
+                                    thd->variables.lock_wait_timeout))
+    DBUG_RETURN(TRUE);
+
+  m_mdl_blocks_commits_lock= mdl_request.ticket;
+  m_state= GRL_ACQUIRED_AND_BLOCKS_COMMIT;
+
+  DBUG_RETURN(FALSE);
 }
 
 
 /**
-  Broadcast COND_global_read_lock.
-
-  TODO/FIXME: Dmitry thinks that we broadcast on COND_global_read_lock
-              when old instance of table is closed to avoid races
-              between incrementing refresh_version and
-              wait_if_global_read_lock(thd, TRUE, FALSE) call.
-              Once global read lock implementation starts using MDL
-              infrastructure this will became unnecessary and should
-              be removed.
+  Set explicit duration for metadata locks which are used to implement GRL.
+
+  @param thd     Reference to thread.
 */
 
-void broadcast_refresh(void)
+void Global_read_lock::set_explicit_lock_duration(THD *thd)
 {
-  mysql_cond_broadcast(&COND_global_read_lock);
+  if (m_mdl_global_shared_lock)
+    thd->mdl_context.set_lock_duration(m_mdl_global_shared_lock, MDL_EXPLICIT);
+  if (m_mdl_blocks_commits_lock)
+    thd->mdl_context.set_lock_duration(m_mdl_blocks_commits_lock, MDL_EXPLICIT);
 }
 
 /**
diff --git a/sql/lock.h b/sql/lock.h
index c097c8d269e..6f779595af8 100644
--- a/sql/lock.h
+++ b/sql/lock.h
@@ -2,6 +2,7 @@
 #define LOCK_INCLUDED
 
 #include "thr_lock.h"                           /* thr_lock_type */
+#include "mdl.h"
 
 // Forward declarations
 struct TABLE;
@@ -18,11 +19,10 @@ void mysql_lock_remove(THD *thd, MYSQL_LOCK *locked,TABLE *table);
 void mysql_lock_abort(THD *thd, TABLE *table, bool upgrade_lock);
 bool mysql_lock_abort_for_thread(THD *thd, TABLE *table);
 MYSQL_LOCK *mysql_lock_merge(MYSQL_LOCK *a,MYSQL_LOCK *b);
-void broadcast_refresh(void);
 /* Lock based on name */
 bool lock_schema_name(THD *thd, const char *db);
 /* Lock based on stored routine name */
-bool lock_routine_name(THD *thd, bool is_function, const char *db,
-                       const char *name);
+bool lock_object_name(THD *thd, MDL_key::enum_mdl_namespace mdl_type,
+                      const char *db, const char *name);
 
 #endif /* LOCK_INCLUDED */
diff --git a/sql/log_event.cc b/sql/log_event.cc
index b4641af07c5..2feb69493a8 100644
--- a/sql/log_event.cc
+++ b/sql/log_event.cc
@@ -4961,6 +4961,8 @@ error:
   */
   if (! thd->in_multi_stmt_transaction_mode())
     thd->mdl_context.release_transactional_locks();
+  else
+    thd->mdl_context.release_statement_locks();
 
   DBUG_EXECUTE_IF("LOAD_DATA_INFILE_has_fatal_error",
                   thd->is_slave_error= 0; thd->is_fatal_error= 1;);
diff --git a/sql/mdl.cc b/sql/mdl.cc
index d53ddcee0c8..3aed54ce12d 100644
--- a/sql/mdl.cc
+++ b/sql/mdl.cc
@@ -68,8 +68,6 @@ static void init_mdl_psi_keys(void)
 }
 #endif /* HAVE_PSI_INTERFACE */
 
-void notify_shared_lock(THD *thd, MDL_ticket *conflicting_ticket);
-
 
 /**
   Thread state names to be used in case when we have to wait on resource
@@ -78,12 +76,14 @@ void notify_shared_lock(THD *thd, MDL_ticket *conflicting_ticket);
 
 const char *MDL_key::m_namespace_to_wait_state_name[NAMESPACE_END]=
 {
-  "Waiting for global metadata lock",
+  "Waiting for global read lock",
   "Waiting for schema metadata lock",
   "Waiting for table metadata lock",
   "Waiting for stored function metadata lock",
   "Waiting for stored procedure metadata lock",
-  NULL
+  "Waiting for trigger metadata lock",
+  "Waiting for event metadata lock",
+  "Waiting for commit lock"
 };
 
 static bool mdl_initialized= 0;
@@ -100,7 +100,6 @@ class MDL_map
 public:
   void init();
   void destroy();
-  MDL_lock *find(const MDL_key *key);
   MDL_lock *find_or_insert(const MDL_key *key);
   void remove(MDL_lock *lock);
 private:
@@ -110,6 +109,10 @@ private:
   HASH m_locks;
   /* Protects access to m_locks hash. */
   mysql_mutex_t m_mutex;
+  /** Pre-allocated MDL_lock object for GLOBAL namespace. */
+  MDL_lock *m_global_lock;
+  /** Pre-allocated MDL_lock object for COMMIT namespace. */
+  MDL_lock *m_commit_lock;
 };
 
 
@@ -354,18 +357,6 @@ public:
 
   inline static MDL_lock *create(const MDL_key *key);
 
-  void notify_shared_locks(MDL_context *ctx)
-  {
-    Ticket_iterator it(m_granted);
-    MDL_ticket *conflicting_ticket;
-
-    while ((conflicting_ticket= it++))
-    {
-      if (conflicting_ticket->get_ctx() != ctx)
-        notify_shared_lock(ctx->get_thd(), conflicting_ticket);
-    }
-  }
-
   void reschedule_waiters();
 
   void remove_ticket(Ticket_list MDL_lock::*queue, MDL_ticket *ticket);
@@ -373,6 +364,9 @@ public:
   bool visit_subgraph(MDL_ticket *waiting_ticket,
                       MDL_wait_for_graph_visitor *gvisitor);
 
+  virtual bool needs_notification(const MDL_ticket *ticket) const = 0;
+  virtual void notify_conflicting_locks(MDL_context *ctx) = 0;
+
   /** List of granted tickets for this lock. */
   Ticket_list m_granted;
   /** Tickets for contexts waiting to acquire a lock. */
@@ -442,6 +436,11 @@ public:
   {
     return m_waiting_incompatible;
   }
+  virtual bool needs_notification(const MDL_ticket *ticket) const
+  {
+    return (ticket->get_type() == MDL_SHARED);
+  }
+  virtual void notify_conflicting_locks(MDL_context *ctx);
 
 private:
   static const bitmap_t m_granted_incompatible[MDL_TYPE_END];
@@ -469,6 +468,11 @@ public:
   {
     return m_waiting_incompatible;
   }
+  virtual bool needs_notification(const MDL_ticket *ticket) const
+  {
+    return ticket->is_upgradable_or_exclusive();
+  }
+  virtual void notify_conflicting_locks(MDL_context *ctx);
 
 private:
   static const bitmap_t m_granted_incompatible[MDL_TYPE_END];
@@ -536,9 +540,14 @@ void mdl_destroy()
 
 void MDL_map::init()
 {
+  MDL_key global_lock_key(MDL_key::GLOBAL, "", "");
+  MDL_key commit_lock_key(MDL_key::COMMIT, "", "");
+
   mysql_mutex_init(key_MDL_map_mutex, &m_mutex, NULL);
   my_hash_init(&m_locks, &my_charset_bin, 16 /* FIXME */, 0, 0,
                mdl_locks_key, 0, 0);
+  m_global_lock= MDL_lock::create(&global_lock_key);
+  m_commit_lock= MDL_lock::create(&commit_lock_key);
 }
 
 
@@ -552,6 +561,8 @@ void MDL_map::destroy()
   DBUG_ASSERT(!m_locks.records);
   mysql_mutex_destroy(&m_mutex);
   my_hash_free(&m_locks);
+  MDL_lock::destroy(m_global_lock);
+  MDL_lock::destroy(m_commit_lock);
 }
 
 
@@ -569,43 +580,28 @@ MDL_lock* MDL_map::find_or_insert(const MDL_key *mdl_key)
   MDL_lock *lock;
   my_hash_value_type hash_value;
 
-  hash_value= my_calc_hash(&m_locks, mdl_key->ptr(), mdl_key->length());
-
-retry:
-  mysql_mutex_lock(&m_mutex);
-  if (!(lock= (MDL_lock*) my_hash_search_using_hash_value(&m_locks,
-                                                          hash_value,
-                                                          mdl_key->ptr(),
-                                                          mdl_key->length())))
+  if (mdl_key->mdl_namespace() == MDL_key::GLOBAL ||
+      mdl_key->mdl_namespace() == MDL_key::COMMIT)
   {
-    lock= MDL_lock::create(mdl_key);
-    if (!lock || my_hash_insert(&m_locks, (uchar*)lock))
-    {
-      mysql_mutex_unlock(&m_mutex);
-      MDL_lock::destroy(lock);
-      return NULL;
-    }
-  }
-
-  if (move_from_hash_to_lock_mutex(lock))
-    goto retry;
+    /*
+      Avoid locking m_mutex when lock for GLOBAL or COMMIT namespace is
+      requested. Return pointer to pre-allocated MDL_lock instance instead.
+      Such an optimization allows to save one mutex lock/unlock for any
+      statement changing data.
 
-  return lock;
-}
+      It works since these namespaces contain only one element so keys
+      for them look like '<namespace-id>\0\0'.
+    */
+    DBUG_ASSERT(mdl_key->length() == 3);
 
+    lock= (mdl_key->mdl_namespace() == MDL_key::GLOBAL) ? m_global_lock :
+                                                          m_commit_lock;
 
-/**
-  Find MDL_lock object corresponding to the key.
+    mysql_prlock_wrlock(&lock->m_rwlock);
 
-  @retval non-NULL - MDL_lock instance for the key with locked
-                     MDL_lock::m_rwlock.
-  @retval NULL     - There was no MDL_lock for the key.
-*/
+    return lock;
+  }
 
-MDL_lock* MDL_map::find(const MDL_key *mdl_key)
-{
-  MDL_lock *lock;
-  my_hash_value_type hash_value;
 
   hash_value= my_calc_hash(&m_locks, mdl_key->ptr(), mdl_key->length());
 
@@ -616,8 +612,13 @@ retry:
                                                           mdl_key->ptr(),
                                                           mdl_key->length())))
   {
-    mysql_mutex_unlock(&m_mutex);
-    return NULL;
+    lock= MDL_lock::create(mdl_key);
+    if (!lock || my_hash_insert(&m_locks, (uchar*)lock))
+    {
+      mysql_mutex_unlock(&m_mutex);
+      MDL_lock::destroy(lock);
+      return NULL;
+    }
   }
 
   if (move_from_hash_to_lock_mutex(lock))
@@ -684,6 +685,17 @@ void MDL_map::remove(MDL_lock *lock)
 {
   uint ref_usage, ref_release;
 
+  if (lock->key.mdl_namespace() == MDL_key::GLOBAL ||
+      lock->key.mdl_namespace() == MDL_key::COMMIT)
+  {
+    /*
+      Never destroy pre-allocated MDL_lock objects for GLOBAL and
+      COMMIT namespaces.
+    */
+    mysql_prlock_unlock(&lock->m_rwlock);
+    return;
+  }
+
   /*
     Destroy the MDL_lock object, but ensure that anyone that is
     holding a reference to the object is not remaining, if so he
@@ -719,8 +731,7 @@ void MDL_map::remove(MDL_lock *lock)
 */
 
 MDL_context::MDL_context()
-  :m_trans_sentinel(NULL),
-  m_thd(NULL),
+  : m_thd(NULL),
   m_needs_thr_lock_abort(FALSE),
   m_waiting_for(NULL)
 {
@@ -742,7 +753,9 @@ MDL_context::MDL_context()
 
 void MDL_context::destroy()
 {
-  DBUG_ASSERT(m_tickets.is_empty());
+  DBUG_ASSERT(m_tickets[MDL_STATEMENT].is_empty() &&
+              m_tickets[MDL_TRANSACTION].is_empty() &&
+              m_tickets[MDL_EXPLICIT].is_empty());
 
   mysql_prlock_destroy(&m_LOCK_waiting_for);
 }
@@ -771,10 +784,12 @@ void MDL_context::destroy()
 void MDL_request::init(MDL_key::enum_mdl_namespace mdl_namespace,
                        const char *db_arg,
                        const char *name_arg,
-                       enum enum_mdl_type mdl_type_arg)
+                       enum_mdl_type mdl_type_arg,
+                       enum_mdl_duration mdl_duration_arg)
 {
   key.mdl_key_init(mdl_namespace, db_arg, name_arg);
   type= mdl_type_arg;
+  duration= mdl_duration_arg;
   ticket= NULL;
 }
 
@@ -789,49 +804,17 @@ void MDL_request::init(MDL_key::enum_mdl_namespace mdl_namespace,
 */
 
 void MDL_request::init(const MDL_key *key_arg,
-                       enum enum_mdl_type mdl_type_arg)
+                       enum_mdl_type mdl_type_arg,
+                       enum_mdl_duration mdl_duration_arg)
 {
   key.mdl_key_init(key_arg);
   type= mdl_type_arg;
+  duration= mdl_duration_arg;
   ticket= NULL;
 }
 
 
 /**
-  Allocate and initialize one lock request.
-
-  Same as mdl_init_lock(), but allocates the lock and the key buffer
-  on a memory root. Necessary to lock ad-hoc tables, e.g.
-  mysql.* tables of grant and data dictionary subsystems.
-
-  @param  mdl_namespace  Id of namespace of object to be locked
-  @param  db             Name of database to which object belongs
-  @param  name           Name of of object
-  @param  root           MEM_ROOT on which object should be allocated
-
-  @note The allocated lock request will have MDL_SHARED type.
-
-  @retval 0      Error if out of memory
-  @retval non-0  Pointer to an object representing a lock request
-*/
-
-MDL_request *
-MDL_request::create(MDL_key::enum_mdl_namespace mdl_namespace, const char *db,
-                    const char *name, enum_mdl_type mdl_type,
-                    MEM_ROOT *root)
-{
-  MDL_request *mdl_request;
-
-  if (!(mdl_request= (MDL_request*) alloc_root(root, sizeof(MDL_request))))
-    return NULL;
-
-  mdl_request->init(mdl_namespace, db, name, mdl_type);
-
-  return mdl_request;
-}
-
-
-/**
   Auxiliary functions needed for creation/destruction of MDL_lock objects.
 
   @note Also chooses an MDL_lock descendant appropriate for object namespace.
@@ -846,6 +829,7 @@ inline MDL_lock *MDL_lock::create(const MDL_key *mdl_key)
   {
     case MDL_key::GLOBAL:
     case MDL_key::SCHEMA:
+    case MDL_key::COMMIT:
       return new MDL_scoped_lock(mdl_key);
     default:
       return new MDL_object_lock(mdl_key);
@@ -867,9 +851,17 @@ void MDL_lock::destroy(MDL_lock *lock)
         on memory allocation by reusing released objects.
 */
 
-MDL_ticket *MDL_ticket::create(MDL_context *ctx_arg, enum_mdl_type type_arg)
+MDL_ticket *MDL_ticket::create(MDL_context *ctx_arg, enum_mdl_type type_arg
+#ifndef DBUG_OFF
+                               , enum_mdl_duration duration_arg
+#endif
+                               )
 {
-  return new MDL_ticket(ctx_arg, type_arg);
+  return new MDL_ticket(ctx_arg, type_arg
+#ifndef DBUG_OFF
+                        , duration_arg
+#endif
+                        );
 }
 
 
@@ -1438,13 +1430,11 @@ bool MDL_ticket::is_incompatible_when_waiting(enum_mdl_type type) const
 /**
   Check whether the context already holds a compatible lock ticket
   on an object.
-  Start searching the transactional locks. If not
-  found in the list of transactional locks, look at LOCK TABLES
-  and HANDLER locks.
+  Start searching from list of locks for the same duration as lock
+  being requested. If not look at lists for other durations.
 
   @param mdl_request  Lock request object for lock to be acquired
-  @param[out] is_transactional FALSE if we pass beyond m_trans_sentinel
-                      while searching for ticket, otherwise TRUE.
+  @param[out] result_duration  Duration of lock which was found.
 
   @note Tickets which correspond to lock types "stronger" than one
         being requested are also considered compatible.
@@ -1454,24 +1444,28 @@ bool MDL_ticket::is_incompatible_when_waiting(enum_mdl_type type) const
 
 MDL_ticket *
 MDL_context::find_ticket(MDL_request *mdl_request,
-                         bool *is_transactional)
+                         enum_mdl_duration *result_duration)
 {
   MDL_ticket *ticket;
-  Ticket_iterator it(m_tickets);
-
-  *is_transactional= TRUE;
+  int i;
 
-  while ((ticket= it++))
+  for (i= 0; i < MDL_DURATION_END; i++)
   {
-    if (ticket == m_trans_sentinel)
-      *is_transactional= FALSE;
+    enum_mdl_duration duration= (enum_mdl_duration)((mdl_request->duration+i) %
+                                                    MDL_DURATION_END);
+    Ticket_iterator it(m_tickets[duration]);
 
-    if (mdl_request->key.is_equal(&ticket->m_lock->key) &&
-        ticket->has_stronger_or_equal_type(mdl_request->type))
-      break;
+    while ((ticket= it++))
+    {
+      if (mdl_request->key.is_equal(&ticket->m_lock->key) &&
+          ticket->has_stronger_or_equal_type(mdl_request->type))
+      {
+        *result_duration= duration;
+        return ticket;
+      }
+    }
   }
-
-  return ticket;
+  return NULL;
 }
 
 
@@ -1549,7 +1543,7 @@ MDL_context::try_acquire_lock_impl(MDL_request *mdl_request,
   MDL_lock *lock;
   MDL_key *key= &mdl_request->key;
   MDL_ticket *ticket;
-  bool is_transactional;
+  enum_mdl_duration found_duration;
 
   DBUG_ASSERT(mdl_request->type != MDL_EXCLUSIVE ||
               is_lock_owner(MDL_key::GLOBAL, "", "", MDL_INTENTION_EXCLUSIVE));
@@ -1563,7 +1557,7 @@ MDL_context::try_acquire_lock_impl(MDL_request *mdl_request,
     Check whether the context already holds a shared lock on the object,
     and if so, grant the request.
   */
-  if ((ticket= find_ticket(mdl_request, &is_transactional)))
+  if ((ticket= find_ticket(mdl_request, &found_duration)))
   {
     DBUG_ASSERT(ticket->m_lock);
     DBUG_ASSERT(ticket->has_stronger_or_equal_type(mdl_request->type));
@@ -1585,7 +1579,9 @@ MDL_context::try_acquire_lock_impl(MDL_request *mdl_request,
       a different alias.
     */
     mdl_request->ticket= ticket;
-    if (!is_transactional && clone_ticket(mdl_request))
+    if ((found_duration != mdl_request->duration ||
+         mdl_request->duration == MDL_EXPLICIT) &&
+        clone_ticket(mdl_request))
     {
       /* Clone failed. */
       mdl_request->ticket= NULL;
@@ -1594,7 +1590,11 @@ MDL_context::try_acquire_lock_impl(MDL_request *mdl_request,
     return FALSE;
   }
 
-  if (!(ticket= MDL_ticket::create(this, mdl_request->type)))
+  if (!(ticket= MDL_ticket::create(this, mdl_request->type
+#ifndef DBUG_OFF
+                                   , mdl_request->duration
+#endif
+                                   )))
     return TRUE;
 
   /* The below call implicitly locks MDL_lock::m_rwlock on success. */
@@ -1612,7 +1612,7 @@ MDL_context::try_acquire_lock_impl(MDL_request *mdl_request,
 
     mysql_prlock_unlock(&lock->m_rwlock);
 
-    m_tickets.push_front(ticket);
+    m_tickets[mdl_request->duration].push_front(ticket);
 
     mdl_request->ticket= ticket;
   }
@@ -1647,7 +1647,11 @@ MDL_context::clone_ticket(MDL_request *mdl_request)
     we effectively downgrade the cloned lock to the level of
     the request.
   */
-  if (!(ticket= MDL_ticket::create(this, mdl_request->type)))
+  if (!(ticket= MDL_ticket::create(this, mdl_request->type
+#ifndef DBUG_OFF
+                                   , mdl_request->duration
+#endif
+                                   )))
     return TRUE;
 
   /* clone() is not supposed to be used to get a stronger lock. */
@@ -1660,36 +1664,74 @@ MDL_context::clone_ticket(MDL_request *mdl_request)
   ticket->m_lock->m_granted.add_ticket(ticket);
   mysql_prlock_unlock(&ticket->m_lock->m_rwlock);
 
-  m_tickets.push_front(ticket);
+  m_tickets[mdl_request->duration].push_front(ticket);
 
   return FALSE;
 }
 
 
 /**
-  Notify a thread holding a shared metadata lock which
-  conflicts with a pending exclusive lock.
+  Notify threads holding a shared metadata locks on object which
+  conflict with a pending X, SNW or SNRW lock.
 
-  @param thd               Current thread context
-  @param conflicting_ticket  Conflicting metadata lock
+  @param  ctx  MDL_context for current thread.
 */
 
-void notify_shared_lock(THD *thd, MDL_ticket *conflicting_ticket)
+void MDL_object_lock::notify_conflicting_locks(MDL_context *ctx)
 {
-  /* Only try to abort locks on which we back off. */
-  if (conflicting_ticket->get_type() < MDL_SHARED_NO_WRITE)
+  Ticket_iterator it(m_granted);
+  MDL_ticket *conflicting_ticket;
+
+  while ((conflicting_ticket= it++))
   {
-    MDL_context *conflicting_ctx= conflicting_ticket->get_ctx();
-    THD *conflicting_thd= conflicting_ctx->get_thd();
-    DBUG_ASSERT(thd != conflicting_thd); /* Self-deadlock */
+    /* Only try to abort locks on which we back off. */
+    if (conflicting_ticket->get_ctx() != ctx &&
+        conflicting_ticket->get_type() < MDL_SHARED_NO_WRITE)
 
-    /*
-      If thread which holds conflicting lock is waiting on table-level
-      lock or some other non-MDL resource we might need to wake it up
-      by calling code outside of MDL.
-    */
-    mysql_notify_thread_having_shared_lock(thd, conflicting_thd,
-                               conflicting_ctx->get_needs_thr_lock_abort());
+    {
+      MDL_context *conflicting_ctx= conflicting_ticket->get_ctx();
+
+      /*
+        If thread which holds conflicting lock is waiting on table-level
+        lock or some other non-MDL resource we might need to wake it up
+        by calling code outside of MDL.
+      */
+      mysql_notify_thread_having_shared_lock(ctx->get_thd(),
+                                 conflicting_ctx->get_thd(),
+                                 conflicting_ctx->get_needs_thr_lock_abort());
+    }
+  }
+}
+
+
+/**
+  Notify threads holding scoped IX locks which conflict with a pending S lock.
+
+  @param  ctx  MDL_context for current thread.
+*/
+
+void MDL_scoped_lock::notify_conflicting_locks(MDL_context *ctx)
+{
+  Ticket_iterator it(m_granted);
+  MDL_ticket *conflicting_ticket;
+
+  while ((conflicting_ticket= it++))
+  {
+    if (conflicting_ticket->get_ctx() != ctx &&
+        conflicting_ticket->get_type() == MDL_INTENTION_EXCLUSIVE)
+
+    {
+      MDL_context *conflicting_ctx= conflicting_ticket->get_ctx();
+
+      /*
+        Thread which holds global IX lock can be a handler thread for
+        insert delayed. We need to kill such threads in order to get
+        global shared lock. We do this my calling code outside of MDL.
+      */
+      mysql_notify_thread_having_shared_lock(ctx->get_thd(),
+                                 conflicting_ctx->get_thd(),
+                                 conflicting_ctx->get_needs_thr_lock_abort());
+    }
   }
 }
 
@@ -1747,8 +1789,8 @@ MDL_context::acquire_lock(MDL_request *mdl_request, ulong lock_wait_timeout)
   */
   m_wait.reset_status();
 
-  if (ticket->is_upgradable_or_exclusive())
-    lock->notify_shared_locks(this);
+  if (lock->needs_notification(ticket))
+    lock->notify_conflicting_locks(this);
 
   mysql_prlock_unlock(&lock->m_rwlock);
 
@@ -1759,7 +1801,7 @@ MDL_context::acquire_lock(MDL_request *mdl_request, ulong lock_wait_timeout)
 
   find_deadlock();
 
-  if (ticket->is_upgradable_or_exclusive())
+  if (lock->needs_notification(ticket))
   {
     struct timespec abs_shortwait;
     set_timespec(abs_shortwait, 1);
@@ -1775,7 +1817,7 @@ MDL_context::acquire_lock(MDL_request *mdl_request, ulong lock_wait_timeout)
         break;
 
       mysql_prlock_wrlock(&lock->m_rwlock);
-      lock->notify_shared_locks(this);
+      lock->notify_conflicting_locks(this);
       mysql_prlock_unlock(&lock->m_rwlock);
       set_timespec(abs_shortwait, 1);
     }
@@ -1818,7 +1860,7 @@ MDL_context::acquire_lock(MDL_request *mdl_request, ulong lock_wait_timeout)
   */
   DBUG_ASSERT(wait_status == MDL_wait::GRANTED);
 
-  m_tickets.push_front(ticket);
+  m_tickets[mdl_request->duration].push_front(ticket);
 
   mdl_request->ticket= ticket;
 
@@ -1859,7 +1901,7 @@ bool MDL_context::acquire_locks(MDL_request_list *mdl_requests,
 {
   MDL_request_list::Iterator it(*mdl_requests);
   MDL_request **sort_buf, **p_req;
-  MDL_ticket *mdl_svp= mdl_savepoint();
+  MDL_savepoint mdl_svp= mdl_savepoint();
   ssize_t req_count= static_cast<ssize_t>(mdl_requests->elements());
 
   if (req_count == 0)
@@ -1928,7 +1970,7 @@ MDL_context::upgrade_shared_lock_to_exclusive(MDL_ticket *mdl_ticket,
                                               ulong lock_wait_timeout)
 {
   MDL_request mdl_xlock_request;
-  MDL_ticket *mdl_svp= mdl_savepoint();
+  MDL_savepoint mdl_svp= mdl_savepoint();
   bool is_new_ticket;
 
   DBUG_ENTER("MDL_ticket::upgrade_shared_lock_to_exclusive");
@@ -1945,7 +1987,8 @@ MDL_context::upgrade_shared_lock_to_exclusive(MDL_ticket *mdl_ticket,
   DBUG_ASSERT(mdl_ticket->m_type == MDL_SHARED_NO_WRITE ||
               mdl_ticket->m_type == MDL_SHARED_NO_READ_WRITE);
 
-  mdl_xlock_request.init(&mdl_ticket->m_lock->key, MDL_EXCLUSIVE);
+  mdl_xlock_request.init(&mdl_ticket->m_lock->key, MDL_EXCLUSIVE,
+                         MDL_TRANSACTION);
 
   if (acquire_lock(&mdl_xlock_request, lock_wait_timeout))
     DBUG_RETURN(TRUE);
@@ -1969,7 +2012,7 @@ MDL_context::upgrade_shared_lock_to_exclusive(MDL_ticket *mdl_ticket,
 
   if (is_new_ticket)
   {
-    m_tickets.remove(mdl_xlock_request.ticket);
+    m_tickets[MDL_TRANSACTION].remove(mdl_xlock_request.ticket);
     MDL_ticket::destroy(mdl_xlock_request.ticket);
   }
 
@@ -2230,10 +2273,12 @@ void MDL_context::find_deadlock()
 /**
   Release lock.
 
-  @param ticket Ticket for lock to be released.
+  @param duration Lock duration.
+  @param ticket   Ticket for lock to be released.
+
 */
 
-void MDL_context::release_lock(MDL_ticket *ticket)
+void MDL_context::release_lock(enum_mdl_duration duration, MDL_ticket *ticket)
 {
   MDL_lock *lock= ticket->m_lock;
   DBUG_ENTER("MDL_context::release_lock");
@@ -2243,12 +2288,9 @@ void MDL_context::release_lock(MDL_ticket *ticket)
   DBUG_ASSERT(this == ticket->get_ctx());
   mysql_mutex_assert_not_owner(&LOCK_open);
 
-  if (ticket == m_trans_sentinel)
-    m_trans_sentinel= ++Ticket_list::Iterator(m_tickets, ticket);
-
   lock->remove_ticket(&MDL_lock::m_granted, ticket);
 
-  m_tickets.remove(ticket);
+  m_tickets[duration].remove(ticket);
   MDL_ticket::destroy(ticket);
 
   DBUG_VOID_RETURN;
@@ -2256,50 +2298,56 @@ void MDL_context::release_lock(MDL_ticket *ticket)
 
 
 /**
+  Release lock with explicit duration.
+
+  @param ticket   Ticket for lock to be released.
+
+*/
+
+void MDL_context::release_lock(MDL_ticket *ticket)
+{
+  DBUG_ASSERT(ticket->m_duration == MDL_EXPLICIT);
+
+  release_lock(MDL_EXPLICIT, ticket);
+}
+
+
+/**
   Release all locks associated with the context. If the sentinel
   is not NULL, do not release locks stored in the list after and
   including the sentinel.
 
-  Transactional locks are added to the beginning of the list, i.e.
-  stored in reverse temporal order. This allows to employ this
-  function to:
+  Statement and transactional locks are added to the beginning of
+  the corresponding lists, i.e. stored in reverse temporal order.
+  This allows to employ this function to:
   - back off in case of a lock conflict.
-  - release all locks in the end of a transaction
+  - release all locks in the end of a statment or transaction
   - rollback to a savepoint.
-
-  The sentinel semantics is used to support LOCK TABLES
-  mode and HANDLER statements: locks taken by these statements
-  survive COMMIT, ROLLBACK, ROLLBACK TO SAVEPOINT.
 */
 
-void MDL_context::release_locks_stored_before(MDL_ticket *sentinel)
+void MDL_context::release_locks_stored_before(enum_mdl_duration duration,
+                                              MDL_ticket *sentinel)
 {
   MDL_ticket *ticket;
-  Ticket_iterator it(m_tickets);
+  Ticket_iterator it(m_tickets[duration]);
   DBUG_ENTER("MDL_context::release_locks_stored_before");
 
-  if (m_tickets.is_empty())
+  if (m_tickets[duration].is_empty())
     DBUG_VOID_RETURN;
 
   while ((ticket= it++) && ticket != sentinel)
   {
     DBUG_PRINT("info", ("found lock to release ticket=%p", ticket));
-    release_lock(ticket);
+    release_lock(duration, ticket);
   }
-  /*
-    If all locks were released, then the sentinel was not present
-    in the list. It must never happen because the sentinel was
-    bogus, i.e. pointed to a ticket that no longer exists.
-  */
-  DBUG_ASSERT(! m_tickets.is_empty() || sentinel == NULL);
 
   DBUG_VOID_RETURN;
 }
 
 
 /**
-  Release all locks in the context which correspond to the same name/
-  object as this lock request.
+  Release all explicit locks in the context which correspond to the
+  same name/object as this lock request.
 
   @param ticket    One of the locks for the name/object for which all
                    locks should be released.
@@ -2312,17 +2360,13 @@ void MDL_context::release_all_locks_for_name(MDL_ticket *name)
 
   /* Remove matching lock tickets from the context. */
   MDL_ticket *ticket;
-  Ticket_iterator it_ticket(m_tickets);
+  Ticket_iterator it_ticket(m_tickets[MDL_EXPLICIT]);
 
   while ((ticket= it_ticket++))
   {
     DBUG_ASSERT(ticket->m_lock);
-    /*
-      We rarely have more than one ticket in this loop,
-      let's not bother saving on pthread_cond_broadcast().
-    */
     if (ticket->m_lock == lock)
-      release_lock(ticket);
+      release_lock(MDL_EXPLICIT, ticket);
   }
 }
 
@@ -2377,9 +2421,10 @@ MDL_context::is_lock_owner(MDL_key::enum_mdl_namespace mdl_namespace,
                            enum_mdl_type mdl_type)
 {
   MDL_request mdl_request;
-  bool is_transactional_unused;
-  mdl_request.init(mdl_namespace, db, name, mdl_type);
-  MDL_ticket *ticket= find_ticket(&mdl_request, &is_transactional_unused);
+  enum_mdl_duration not_unused;
+  /* We don't care about exact duration of lock here. */
+  mdl_request.init(mdl_namespace, db, name, mdl_type, MDL_TRANSACTION);
+  MDL_ticket *ticket= find_ticket(&mdl_request, &not_unused);
 
   DBUG_ASSERT(ticket == NULL || ticket->m_lock);
 
@@ -2408,18 +2453,15 @@ bool MDL_ticket::has_pending_conflicting_lock() const
   @note It's safe to iterate and unlock any locks after taken after this
         savepoint because other statements that take other special locks
         cause a implicit commit (ie LOCK TABLES).
-
-  @param mdl_savepont  The last acquired MDL lock when the
-                       savepoint was set.
 */
 
-void MDL_context::rollback_to_savepoint(MDL_ticket *mdl_savepoint)
+void MDL_context::rollback_to_savepoint(const MDL_savepoint &mdl_savepoint)
 {
   DBUG_ENTER("MDL_context::rollback_to_savepoint");
 
   /* If savepoint is NULL, it is from the start of the transaction. */
-  release_locks_stored_before(mdl_savepoint ?
-                              mdl_savepoint : m_trans_sentinel);
+  release_locks_stored_before(MDL_STATEMENT, mdl_savepoint.m_stmt_ticket);
+  release_locks_stored_before(MDL_TRANSACTION, mdl_savepoint.m_trans_ticket);
 
   DBUG_VOID_RETURN;
 }
@@ -2437,65 +2479,150 @@ void MDL_context::rollback_to_savepoint(MDL_ticket *mdl_savepoint)
 void MDL_context::release_transactional_locks()
 {
   DBUG_ENTER("MDL_context::release_transactional_locks");
-  release_locks_stored_before(m_trans_sentinel);
+  release_locks_stored_before(MDL_STATEMENT, NULL);
+  release_locks_stored_before(MDL_TRANSACTION, NULL);
+  DBUG_VOID_RETURN;
+}
+
+
+void MDL_context::release_statement_locks()
+{
+  DBUG_ENTER("MDL_context::release_transactional_locks");
+  release_locks_stored_before(MDL_STATEMENT, NULL);
   DBUG_VOID_RETURN;
 }
 
 
 /**
   Does this savepoint have this lock?
-  
-  @retval TRUE  The ticket is older than the savepoint and
-                is not LT, HA or GLR ticket. Thus it belongs
-                to the savepoint.
-  @retval FALSE The ticket is newer than the savepoint
-                or is an LT, HA or GLR ticket.
+
+  @retval TRUE  The ticket is older than the savepoint or
+                is an LT, HA or GLR ticket. Thus it belongs
+                to the savepoint or has explicit duration.
+  @retval FALSE The ticket is newer than the savepoint.
+                and is not an LT, HA or GLR ticket.
 */
 
-bool MDL_context::has_lock(MDL_ticket *mdl_savepoint,
+bool MDL_context::has_lock(const MDL_savepoint &mdl_savepoint,
                            MDL_ticket *mdl_ticket)
 {
   MDL_ticket *ticket;
   /* Start from the beginning, most likely mdl_ticket's been just acquired. */
-  MDL_context::Ticket_iterator it(m_tickets);
-  bool found_savepoint= FALSE;
+  MDL_context::Ticket_iterator s_it(m_tickets[MDL_STATEMENT]);
+  MDL_context::Ticket_iterator t_it(m_tickets[MDL_TRANSACTION]);
 
-  while ((ticket= it++) && ticket != m_trans_sentinel)
+  while ((ticket= s_it++) && ticket != mdl_savepoint.m_stmt_ticket)
   {
-    /*
-      First met the savepoint. The ticket must be
-      somewhere after it.
-    */
-    if (ticket == mdl_savepoint)
-      found_savepoint= TRUE;
-    /*
-      Met the ticket. If we haven't yet met the savepoint,
-      the ticket is newer than the savepoint.
-    */
     if (ticket == mdl_ticket)
-      return found_savepoint;
+      return FALSE;
   }
-  /* Reached m_trans_sentinel. The ticket must be LT, HA or GRL ticket. */
-  return FALSE;
+
+  while ((ticket= t_it++) && ticket != mdl_savepoint.m_trans_ticket)
+  {
+    if (ticket == mdl_ticket)
+      return FALSE;
+  }
+  return TRUE;
+}
+
+
+/**
+  Change lock duration for transactional lock.
+
+  @param ticket   Ticket representing lock.
+  @param duration Lock duration to be set.
+
+  @note This method only supports changing duration of
+        transactional lock to some other duration.
+*/
+
+void MDL_context::set_lock_duration(MDL_ticket *mdl_ticket,
+                                    enum_mdl_duration duration)
+{
+  DBUG_ASSERT(mdl_ticket->m_duration == MDL_TRANSACTION &&
+              duration != MDL_TRANSACTION);
+
+  m_tickets[MDL_TRANSACTION].remove(mdl_ticket);
+  m_tickets[duration].push_front(mdl_ticket);
+#ifndef DBUG_OFF
+  mdl_ticket->m_duration= duration;
+#endif
 }
 
 
 /**
-  Rearrange the ticket to reside in the part of the list that's
-  beyond m_trans_sentinel. This effectively changes the ticket
-  life cycle, from automatic to manual: i.e. the ticket is no
-  longer released by MDL_context::release_transactional_locks() or
-  MDL_context::rollback_to_savepoint(), it must be released manually.
+  Set explicit duration for all locks in the context.
 */
 
-void MDL_context::move_ticket_after_trans_sentinel(MDL_ticket *mdl_ticket)
+void MDL_context::set_explicit_duration_for_all_locks()
 {
-  m_tickets.remove(mdl_ticket);
-  if (m_trans_sentinel == NULL)
+  int i;
+  MDL_ticket *ticket;
+
+  /*
+    In the most common case when this function is called list
+    of transactional locks is bigger than list of locks with
+    explicit duration. So we start by swapping these two lists
+    and then move elements from new list of transactional
+    locks and list of statement locks to list of locks with
+    explicit duration.
+  */
+
+  m_tickets[MDL_EXPLICIT].swap(m_tickets[MDL_TRANSACTION]);
+
+  for (i= 0; i < MDL_EXPLICIT; i++)
   {
-    m_trans_sentinel= mdl_ticket;
-    m_tickets.push_back(mdl_ticket);
+    Ticket_iterator it_ticket(m_tickets[i]);
+
+    while ((ticket= it_ticket++))
+    {
+      m_tickets[i].remove(ticket);
+      m_tickets[MDL_EXPLICIT].push_front(ticket);
+    }
   }
-  else
-    m_tickets.insert_after(m_trans_sentinel, mdl_ticket);
+
+#ifndef DBUG_OFF
+  Ticket_iterator exp_it(m_tickets[MDL_EXPLICIT]);
+
+  while ((ticket= exp_it++))
+    ticket->m_duration= MDL_EXPLICIT;
+#endif
+}
+
+
+/**
+  Set transactional duration for all locks in the context.
+*/
+
+void MDL_context::set_transaction_duration_for_all_locks()
+{
+  MDL_ticket *ticket;
+
+  /*
+    In the most common case when this function is called list
+    of explicit locks is bigger than two other lists (in fact,
+    list of statement locks is always empty). So we start by
+    swapping list of explicit and transactional locks and then
+    move contents of new list of explicit locks to list of
+    locks with transactional duration.
+  */
+
+  DBUG_ASSERT(m_tickets[MDL_STATEMENT].is_empty());
+
+  m_tickets[MDL_TRANSACTION].swap(m_tickets[MDL_EXPLICIT]);
+
+  Ticket_iterator it_ticket(m_tickets[MDL_EXPLICIT]);
+
+  while ((ticket= it_ticket++))
+  {
+    m_tickets[MDL_EXPLICIT].remove(ticket);
+    m_tickets[MDL_TRANSACTION].push_front(ticket);
+  }
+
+#ifndef DBUG_OFF
+  Ticket_iterator trans_it(m_tickets[MDL_TRANSACTION]);
+
+  while ((ticket= trans_it++))
+    ticket->m_duration= MDL_TRANSACTION;
+#endif
 }
diff --git a/sql/mdl.h b/sql/mdl.h
index 7938d833eac..ff30746e739 100644
--- a/sql/mdl.h
+++ b/sql/mdl.h
@@ -150,6 +150,15 @@ enum enum_mdl_type {
   MDL_TYPE_END};
 
 
+/** Duration of metadata lock. */
+
+enum enum_mdl_duration { MDL_STATEMENT= 0,
+                         MDL_TRANSACTION,
+                         MDL_EXPLICIT,
+                         /* This should be the last ! */
+                         MDL_DURATION_END };
+
+
 /** Maximal length of key for metadata locking subsystem. */
 #define MAX_MDLKEY_LENGTH (1 + NAME_LEN + 1 + NAME_LEN + 1)
 
@@ -167,13 +176,16 @@ class MDL_key
 {
 public:
   /**
-    Object namespaces
+    Object namespaces.
+    Sic: when adding a new member to this enum make sure to
+    update m_namespace_to_wait_state_name array in mdl.cc!
 
     Different types of objects exist in different namespaces
      - TABLE is for tables and views.
      - FUNCTION is for stored functions.
      - PROCEDURE is for stored procedures.
      - TRIGGER is for triggers.
+     - EVENT is for event scheduler events
     Note that although there isn't metadata locking on triggers,
     it's necessary to have a separate namespace for them since
     MDL_key is also used outside of the MDL subsystem.
@@ -184,6 +196,8 @@ public:
                             FUNCTION,
                             PROCEDURE,
                             TRIGGER,
+                            EVENT,
+                            COMMIT,
                             /* This should be the last ! */
                             NAMESPACE_END };
 
@@ -305,6 +319,8 @@ class MDL_request
 public:
   /** Type of metadata lock. */
   enum          enum_mdl_type type;
+  /** Duration for requested lock. */
+  enum enum_mdl_duration duration;
 
   /**
     Pointers for participating in the list of lock requests for this context.
@@ -327,17 +343,16 @@ public:
 
   void init(MDL_key::enum_mdl_namespace namespace_arg,
             const char *db_arg, const char *name_arg,
-            enum_mdl_type mdl_type_arg);
-  void init(const MDL_key *key_arg, enum_mdl_type mdl_type_arg);
+            enum_mdl_type mdl_type_arg,
+            enum_mdl_duration mdl_duration_arg);
+  void init(const MDL_key *key_arg, enum_mdl_type mdl_type_arg,
+            enum_mdl_duration mdl_duration_arg);
   /** Set type of lock request. Can be only applied to pending locks. */
   inline void set_type(enum_mdl_type type_arg)
   {
     DBUG_ASSERT(ticket == NULL);
     type= type_arg;
   }
-  static MDL_request *create(MDL_key::enum_mdl_namespace mdl_namespace,
-                             const char *db, const char *name,
-                             enum_mdl_type mdl_type, MEM_ROOT *root);
 
   /*
     This is to work around the ugliness of TABLE_LIST
@@ -363,6 +378,7 @@ public:
 
   MDL_request(const MDL_request *rhs)
     :type(rhs->type),
+    duration(rhs->duration),
     ticket(NULL),
     key(&rhs->key)
   {}
@@ -484,17 +500,35 @@ public:
 private:
   friend class MDL_context;
 
-  MDL_ticket(MDL_context *ctx_arg, enum_mdl_type type_arg)
+  MDL_ticket(MDL_context *ctx_arg, enum_mdl_type type_arg
+#ifndef DBUG_OFF
+             , enum_mdl_duration duration_arg
+#endif
+            )
    : m_type(type_arg),
+#ifndef DBUG_OFF
+     m_duration(duration_arg),
+#endif
      m_ctx(ctx_arg),
      m_lock(NULL)
   {}
 
-  static MDL_ticket *create(MDL_context *ctx_arg, enum_mdl_type type_arg);
+  static MDL_ticket *create(MDL_context *ctx_arg, enum_mdl_type type_arg
+#ifndef DBUG_OFF
+                            , enum_mdl_duration duration_arg
+#endif
+                            );
   static void destroy(MDL_ticket *ticket);
 private:
   /** Type of metadata lock. Externally accessible. */
   enum enum_mdl_type m_type;
+#ifndef DBUG_OFF
+  /**
+    Duration of lock represented by this ticket.
+    Context private. Debug-only.
+  */
+  enum_mdl_duration m_duration;
+#endif
   /**
     Context of the owner of the metadata lock ticket. Externally accessible.
   */
@@ -512,6 +546,39 @@ private:
 
 
 /**
+  Savepoint for MDL context.
+
+  Doesn't include metadata locks with explicit duration as
+  they are not released during rollback to savepoint.
+*/
+
+class MDL_savepoint
+{
+public:
+  MDL_savepoint() {};
+
+private:
+  MDL_savepoint(MDL_ticket *stmt_ticket, MDL_ticket *trans_ticket)
+    : m_stmt_ticket(stmt_ticket), m_trans_ticket(trans_ticket)
+  {}
+
+  friend class MDL_context;
+
+private:
+  /**
+    Pointer to last lock with statement duration which was taken
+    before creation of savepoint.
+  */
+  MDL_ticket *m_stmt_ticket;
+  /**
+    Pointer to last lock with transaction duration which was taken
+    before creation of savepoint.
+  */
+  MDL_ticket *m_trans_ticket;
+};
+
+
+/**
   A reliable way to wait on an MDL lock.
 */
 
@@ -559,9 +626,7 @@ public:
   typedef I_P_List<MDL_ticket,
                    I_P_List_adapter<MDL_ticket,
                                     &MDL_ticket::next_in_context,
-                                    &MDL_ticket::prev_in_context>,
-                   I_P_List_null_counter,
-                   I_P_List_fast_push_back<MDL_ticket> >
+                                    &MDL_ticket::prev_in_context> >
           Ticket_list;
 
   typedef Ticket_list::Iterator Ticket_iterator;
@@ -584,37 +649,28 @@ public:
                      const char *db, const char *name,
                      enum_mdl_type mdl_type);
 
-  bool has_lock(MDL_ticket *mdl_savepoint, MDL_ticket *mdl_ticket);
+  bool has_lock(const MDL_savepoint &mdl_savepoint, MDL_ticket *mdl_ticket);
 
   inline bool has_locks() const
   {
-    return !m_tickets.is_empty();
-  }
-
-  MDL_ticket *mdl_savepoint()
-  {
-    /*
-      NULL savepoint represents the start of the transaction.
-      Checking for m_trans_sentinel also makes sure we never
-      return a pointer to HANDLER ticket as a savepoint.
-    */
-    return m_tickets.front() == m_trans_sentinel ? NULL : m_tickets.front();
+    return !(m_tickets[MDL_STATEMENT].is_empty() &&
+             m_tickets[MDL_TRANSACTION].is_empty() &&
+             m_tickets[MDL_EXPLICIT].is_empty());
   }
 
-  void set_trans_sentinel()
+  MDL_savepoint mdl_savepoint()
   {
-    m_trans_sentinel= m_tickets.front();
+    return MDL_savepoint(m_tickets[MDL_STATEMENT].front(),
+                         m_tickets[MDL_TRANSACTION].front());
   }
-  MDL_ticket *trans_sentinel() const { return m_trans_sentinel; }
 
-  void reset_trans_sentinel(MDL_ticket *sentinel_arg)
-  {
-    m_trans_sentinel= sentinel_arg;
-  }
-  void move_ticket_after_trans_sentinel(MDL_ticket *mdl_ticket);
+  void set_explicit_duration_for_all_locks();
+  void set_transaction_duration_for_all_locks();
+  void set_lock_duration(MDL_ticket *mdl_ticket, enum_mdl_duration duration);
 
+  void release_statement_locks();
   void release_transactional_locks();
-  void rollback_to_savepoint(MDL_ticket *mdl_savepoint);
+  void rollback_to_savepoint(const MDL_savepoint &mdl_savepoint);
 
   inline THD *get_thd() const { return m_thd; }
 
@@ -655,46 +711,43 @@ public:
   MDL_wait m_wait;
 private:
   /**
-    All MDL tickets acquired by this connection.
-
-    The order of tickets in m_tickets list.
-    ---------------------------------------
-    The entire set of locks acquired by a connection
-    can be separated in two subsets: transactional and
-    non-transactional locks.
-
-    Transactional locks are locks with automatic scope. They
-    are accumulated in the course of a transaction, and
-    released only on COMMIT, ROLLBACK or ROLLBACK TO SAVEPOINT.
-    They must not be (and never are) released manually,
+    Lists of all MDL tickets acquired by this connection.
+
+    Lists of MDL tickets:
+    ---------------------
+    The entire set of locks acquired by a connection can be separated
+    in three subsets according to their: locks released at the end of
+    statement, at the end of transaction and locks are released
+    explicitly.
+
+    Statement and transactional locks are locks with automatic scope.
+    They are accumulated in the course of a transaction, and released
+    either at the end of uppermost statement (for statement locks) or
+    on COMMIT, ROLLBACK or ROLLBACK TO SAVEPOINT (for transactional
+    locks). They must not be (and never are) released manually,
     i.e. with release_lock() call.
 
-    Non-transactional locks are taken for locks that span
+    Locks with explicit duration are taken for locks that span
     multiple transactions or savepoints.
     These are: HANDLER SQL locks (HANDLER SQL is
     transaction-agnostic), LOCK TABLES locks (you can COMMIT/etc
     under LOCK TABLES, and the locked tables stay locked), and
-    SET GLOBAL READ_ONLY=1 global shared lock.
+    locks implementing "global read lock".
 
-    Transactional locks are always prepended to the beginning
-    of the list. In other words, they are stored in reverse
-    temporal order. Thus, when we rollback to a savepoint,
-    we start popping and releasing tickets from the front
-    until we reach the last ticket acquired after the
-    savepoint.
+    Statement/transactional locks are always prepended to the
+    beginning of the appropriate list. In other words, they are
+    stored in reverse temporal order. Thus, when we rollback to
+    a savepoint, we start popping and releasing tickets from the
+    front until we reach the last ticket acquired after the savepoint.
 
-    Non-transactional locks are always stored after
-    transactional ones, and among each other can be
-    split into three sets:
+    Locks with explicit duration stored are not stored in any
+    particular order, and among each other can be split into
+    three sets:
 
     [LOCK TABLES locks] [HANDLER locks] [GLOBAL READ LOCK locks]
 
     The following is known about these sets:
 
-    * we can never have both HANDLER and LOCK TABLES locks
-      together -- HANDLER statements are prohibited under LOCK
-      TABLES, entering LOCK TABLES implicitly closes all open
-      HANDLERs.
     * GLOBAL READ LOCK locks are always stored after LOCK TABLES
       locks and after HANDLER locks. This is because one can't say
       SET GLOBAL read_only=1 or FLUSH TABLES WITH READ LOCK
@@ -709,14 +762,9 @@ private:
       However, one can open a few HANDLERs after entering the
       read only mode.
     * LOCK TABLES locks include intention exclusive locks on
-      involved schemas.
-  */
-  Ticket_list m_tickets;
-  /**
-    Separates transactional and non-transactional locks
-    in m_tickets list, @sa m_tickets.
+      involved schemas and global intention exclusive lock.
   */
-  MDL_ticket *m_trans_sentinel;
+  Ticket_list m_tickets[MDL_DURATION_END];
   THD *m_thd;
   /**
     TRUE -  if for this context we will break protocol and try to
@@ -747,8 +795,9 @@ private:
   MDL_wait_for_subgraph *m_waiting_for;
 private:
   MDL_ticket *find_ticket(MDL_request *mdl_req,
-                          bool *is_transactional);
-  void release_locks_stored_before(MDL_ticket *sentinel);
+                          enum_mdl_duration *duration);
+  void release_locks_stored_before(enum_mdl_duration duration, MDL_ticket *sentinel);
+  void release_lock(enum_mdl_duration duration, MDL_ticket *ticket);
   bool try_acquire_lock_impl(MDL_request *mdl_request,
                              MDL_ticket **out_ticket);
 
diff --git a/sql/mysqld.cc b/sql/mysqld.cc
index 21754b23940..9e4026f3a1c 100644
--- a/sql/mysqld.cc
+++ b/sql/mysqld.cc
@@ -604,8 +604,7 @@ pthread_key(MEM_ROOT**,THR_MALLOC);
 pthread_key(THD*, THR_THD);
 mysql_mutex_t LOCK_thread_count;
 mysql_mutex_t
-  LOCK_status, LOCK_global_read_lock,
-  LOCK_error_log, LOCK_uuid_generator,
+  LOCK_status, LOCK_error_log, LOCK_uuid_generator,
   LOCK_delayed_insert, LOCK_delayed_status, LOCK_delayed_create,
   LOCK_crypt,
   LOCK_global_system_variables,
@@ -625,7 +624,6 @@ mysql_mutex_t LOCK_des_key_file;
 mysql_rwlock_t LOCK_grant, LOCK_sys_init_connect, LOCK_sys_init_slave;
 mysql_rwlock_t LOCK_system_variables_hash;
 mysql_cond_t COND_thread_count;
-mysql_cond_t COND_global_read_lock;
 pthread_t signal_thread;
 pthread_attr_t connection_attrib;
 mysql_mutex_t LOCK_server_started;
@@ -1542,7 +1540,6 @@ static void clean_up_mutexes()
   mysql_mutex_destroy(&LOCK_crypt);
   mysql_mutex_destroy(&LOCK_user_conn);
   mysql_mutex_destroy(&LOCK_connection_count);
-  Events::destroy_mutexes();
 #ifdef HAVE_OPENSSL
   mysql_mutex_destroy(&LOCK_des_key_file);
 #ifndef HAVE_YASSL
@@ -1560,12 +1557,10 @@ static void clean_up_mutexes()
   mysql_rwlock_destroy(&LOCK_sys_init_slave);
   mysql_mutex_destroy(&LOCK_global_system_variables);
   mysql_rwlock_destroy(&LOCK_system_variables_hash);
-  mysql_mutex_destroy(&LOCK_global_read_lock);
   mysql_mutex_destroy(&LOCK_uuid_generator);
   mysql_mutex_destroy(&LOCK_prepared_stmt_count);
   mysql_mutex_destroy(&LOCK_error_messages);
   mysql_cond_destroy(&COND_thread_count);
-  mysql_cond_destroy(&COND_global_read_lock);
   mysql_cond_destroy(&COND_thread_cache);
   mysql_cond_destroy(&COND_flush_thread_cache);
   mysql_cond_destroy(&COND_manager);
@@ -3524,8 +3519,6 @@ static int init_thread_environment()
                    &LOCK_global_system_variables, MY_MUTEX_INIT_FAST);
   mysql_rwlock_init(key_rwlock_LOCK_system_variables_hash,
                     &LOCK_system_variables_hash);
-  mysql_mutex_init(key_LOCK_global_read_lock,
-                   &LOCK_global_read_lock, MY_MUTEX_INIT_FAST);
   mysql_mutex_init(key_LOCK_prepared_stmt_count,
                    &LOCK_prepared_stmt_count, MY_MUTEX_INIT_FAST);
   mysql_mutex_init(key_LOCK_error_messages,
@@ -3553,7 +3546,6 @@ static int init_thread_environment()
   mysql_rwlock_init(key_rwlock_LOCK_sys_init_slave, &LOCK_sys_init_slave);
   mysql_rwlock_init(key_rwlock_LOCK_grant, &LOCK_grant);
   mysql_cond_init(key_COND_thread_count, &COND_thread_count, NULL);
-  mysql_cond_init(key_COND_global_read_lock, &COND_global_read_lock, NULL);
   mysql_cond_init(key_COND_thread_cache, &COND_thread_cache, NULL);
   mysql_cond_init(key_COND_flush_thread_cache, &COND_flush_thread_cache, NULL);
   mysql_cond_init(key_COND_manager, &COND_manager, NULL);
@@ -7669,7 +7661,7 @@ PSI_mutex_key key_BINLOG_LOCK_index, key_BINLOG_LOCK_prep_xids,
   key_delayed_insert_mutex, key_hash_filo_lock, key_LOCK_active_mi,
   key_LOCK_connection_count, key_LOCK_crypt, key_LOCK_delayed_create,
   key_LOCK_delayed_insert, key_LOCK_delayed_status, key_LOCK_error_log,
-  key_LOCK_gdl, key_LOCK_global_read_lock, key_LOCK_global_system_variables,
+  key_LOCK_gdl, key_LOCK_global_system_variables,
   key_LOCK_manager,
   key_LOCK_prepared_stmt_count,
   key_LOCK_rpl_status, key_LOCK_server_started, key_LOCK_status,
@@ -7707,7 +7699,6 @@ static PSI_mutex_info all_server_mutexes[]=
   { &key_LOCK_delayed_status, "LOCK_delayed_status", PSI_FLAG_GLOBAL},
   { &key_LOCK_error_log, "LOCK_error_log", PSI_FLAG_GLOBAL},
   { &key_LOCK_gdl, "LOCK_gdl", PSI_FLAG_GLOBAL},
-  { &key_LOCK_global_read_lock, "LOCK_global_read_lock", PSI_FLAG_GLOBAL},
   { &key_LOCK_global_system_variables, "LOCK_global_system_variables", PSI_FLAG_GLOBAL},
   { &key_LOCK_manager, "LOCK_manager", PSI_FLAG_GLOBAL},
   { &key_LOCK_prepared_stmt_count, "LOCK_prepared_stmt_count", PSI_FLAG_GLOBAL},
@@ -7756,7 +7747,7 @@ PSI_cond_key key_PAGE_cond, key_COND_active, key_COND_pool;
 #endif /* HAVE_MMAP */
 
 PSI_cond_key key_BINLOG_COND_prep_xids, key_BINLOG_update_cond,
-  key_COND_cache_status_changed, key_COND_global_read_lock, key_COND_manager,
+  key_COND_cache_status_changed, key_COND_manager,
   key_COND_rpl_status, key_COND_server_started,
   key_delayed_insert_cond, key_delayed_insert_cond_client,
   key_item_func_sleep_cond, key_master_info_data_cond,
@@ -7779,7 +7770,6 @@ static PSI_cond_info all_server_conds[]=
   { &key_BINLOG_COND_prep_xids, "MYSQL_BIN_LOG::COND_prep_xids", 0},
   { &key_BINLOG_update_cond, "MYSQL_BIN_LOG::update_cond", 0},
   { &key_COND_cache_status_changed, "Query_cache::COND_cache_status_changed", 0},
-  { &key_COND_global_read_lock, "COND_global_read_lock", PSI_FLAG_GLOBAL},
   { &key_COND_manager, "COND_manager", PSI_FLAG_GLOBAL},
   { &key_COND_rpl_status, "COND_rpl_status", PSI_FLAG_GLOBAL},
   { &key_COND_server_started, "COND_server_started", PSI_FLAG_GLOBAL},
diff --git a/sql/mysqld.h b/sql/mysqld.h
index dc9f94c0d03..5e65d0d2a8d 100644
--- a/sql/mysqld.h
+++ b/sql/mysqld.h
@@ -100,7 +100,7 @@ extern bool opt_ignore_builtin_innodb;
 extern my_bool opt_character_set_client_handshake;
 extern bool volatile abort_loop;
 extern bool in_bootstrap;
-extern uint volatile thread_count, global_read_lock;
+extern uint volatile thread_count;
 extern uint connection_count;
 extern my_bool opt_safe_user_create;
 extern my_bool opt_safe_show_db, opt_local_infile, opt_myisam_use_mmap;
@@ -227,7 +227,7 @@ extern PSI_mutex_key key_BINLOG_LOCK_index, key_BINLOG_LOCK_prep_xids,
   key_delayed_insert_mutex, key_hash_filo_lock, key_LOCK_active_mi,
   key_LOCK_connection_count, key_LOCK_crypt, key_LOCK_delayed_create,
   key_LOCK_delayed_insert, key_LOCK_delayed_status, key_LOCK_error_log,
-  key_LOCK_gdl, key_LOCK_global_read_lock, key_LOCK_global_system_variables,
+  key_LOCK_gdl, key_LOCK_global_system_variables,
   key_LOCK_logger, key_LOCK_manager,
   key_LOCK_prepared_stmt_count,
   key_LOCK_rpl_status, key_LOCK_server_started, key_LOCK_status,
@@ -248,7 +248,7 @@ extern PSI_cond_key key_PAGE_cond, key_COND_active, key_COND_pool;
 #endif /* HAVE_MMAP */
 
 extern PSI_cond_key key_BINLOG_COND_prep_xids, key_BINLOG_update_cond,
-  key_COND_cache_status_changed, key_COND_global_read_lock, key_COND_manager,
+  key_COND_cache_status_changed, key_COND_manager,
   key_COND_rpl_status, key_COND_server_started,
   key_delayed_insert_cond, key_delayed_insert_cond_client,
   key_item_func_sleep_cond, key_master_info_data_cond,
@@ -320,7 +320,7 @@ extern mysql_mutex_t
        LOCK_user_locks, LOCK_status,
        LOCK_error_log, LOCK_delayed_insert, LOCK_uuid_generator,
        LOCK_delayed_status, LOCK_delayed_create, LOCK_crypt, LOCK_timezone,
-       LOCK_slave_list, LOCK_active_mi, LOCK_manager, LOCK_global_read_lock,
+       LOCK_slave_list, LOCK_active_mi, LOCK_manager,
        LOCK_global_system_variables, LOCK_user_conn,
        LOCK_prepared_stmt_count, LOCK_error_messages, LOCK_connection_count;
 extern MYSQL_PLUGIN_IMPORT mysql_mutex_t LOCK_thread_count;
@@ -333,7 +333,6 @@ extern mysql_rwlock_t LOCK_grant, LOCK_sys_init_connect, LOCK_sys_init_slave;
 extern mysql_rwlock_t LOCK_system_variables_hash;
 extern mysql_cond_t COND_thread_count;
 extern mysql_cond_t COND_manager;
-extern mysql_cond_t COND_global_read_lock;
 extern int32 thread_running;
 extern my_atomic_rwlock_t thread_running_lock;
 
diff --git a/sql/rpl_rli.cc b/sql/rpl_rli.cc
index af9b452acd8..a35e7bb1612 100644
--- a/sql/rpl_rli.cc
+++ b/sql/rpl_rli.cc
@@ -1274,6 +1274,9 @@ void Relay_log_info::slave_close_thread_tables(THD *thd)
   */
   if (! thd->in_multi_stmt_transaction_mode())
     thd->mdl_context.release_transactional_locks();
+  else
+    thd->mdl_context.release_statement_locks();
+
   clear_tables_to_lock();
 }
 #endif
diff --git a/sql/sp.cc b/sql/sp.cc
index 7385a6ffcae..4dea6843ef1 100644
--- a/sql/sp.cc
+++ b/sql/sp.cc
@@ -27,7 +27,7 @@
 #include "sql_acl.h"                       // SUPER_ACL
 #include "sp_head.h"
 #include "sp_cache.h"
-#include "lock.h"                               // lock_routine_name
+#include "lock.h"                               // lock_object_name
 
 #include <my_user.h>
 
@@ -440,7 +440,7 @@ static TABLE *open_proc_table_for_update(THD *thd)
 {
   TABLE_LIST table_list;
   TABLE *table;
-  MDL_ticket *mdl_savepoint= thd->mdl_context.mdl_savepoint();
+  MDL_savepoint mdl_savepoint= thd->mdl_context.mdl_savepoint();
   DBUG_ENTER("open_proc_table_for_update");
 
   table_list.init_one_table("mysql", 5, "proc", 4, "proc", TL_WRITE);
@@ -925,6 +925,8 @@ sp_create_routine(THD *thd, int type, sp_head *sp)
   TABLE *table;
   char definer[USER_HOST_BUFF_SIZE];
   ulong saved_mode= thd->variables.sql_mode;
+  MDL_key::enum_mdl_namespace mdl_type= type == TYPE_ENUM_FUNCTION ?
+                                        MDL_key::FUNCTION : MDL_key::PROCEDURE;
 
   CHARSET_INFO *db_cs= get_default_db_collation(thd, sp->m_db.str);
 
@@ -944,8 +946,7 @@ sp_create_routine(THD *thd, int type, sp_head *sp)
               type == TYPE_ENUM_FUNCTION);
 
   /* Grab an exclusive MDL lock. */
-  if (lock_routine_name(thd, type == TYPE_ENUM_FUNCTION,
-                        sp->m_db.str, sp->m_name.str))
+  if (lock_object_name(thd, mdl_type, sp->m_db.str, sp->m_name.str))
     DBUG_RETURN(SP_OPEN_TABLE_FAILED);
 
   /* Reset sql_mode during data dictionary operations. */
@@ -1193,6 +1194,8 @@ sp_drop_routine(THD *thd, int type, sp_name *name)
   TABLE *table;
   int ret;
   bool save_binlog_row_based;
+  MDL_key::enum_mdl_namespace mdl_type= type == TYPE_ENUM_FUNCTION ?
+                                        MDL_key::FUNCTION : MDL_key::PROCEDURE;
   DBUG_ENTER("sp_drop_routine");
   DBUG_PRINT("enter", ("type: %d  name: %.*s",
 		       type, (int) name->m_name.length, name->m_name.str));
@@ -1201,8 +1204,7 @@ sp_drop_routine(THD *thd, int type, sp_name *name)
               type == TYPE_ENUM_FUNCTION);
 
   /* Grab an exclusive MDL lock. */
-  if (lock_routine_name(thd, type == TYPE_ENUM_FUNCTION,
-                        name->m_db.str, name->m_name.str))
+  if (lock_object_name(thd, mdl_type, name->m_db.str, name->m_name.str))
     DBUG_RETURN(SP_DELETE_ROW_FAILED);
 
   if (!(table= open_proc_table_for_update(thd)))
@@ -1273,6 +1275,8 @@ sp_update_routine(THD *thd, int type, sp_name *name, st_sp_chistics *chistics)
   TABLE *table;
   int ret;
   bool save_binlog_row_based;
+  MDL_key::enum_mdl_namespace mdl_type= type == TYPE_ENUM_FUNCTION ?
+                                        MDL_key::FUNCTION : MDL_key::PROCEDURE;
   DBUG_ENTER("sp_update_routine");
   DBUG_PRINT("enter", ("type: %d  name: %.*s",
 		       type, (int) name->m_name.length, name->m_name.str));
@@ -1281,8 +1285,7 @@ sp_update_routine(THD *thd, int type, sp_name *name, st_sp_chistics *chistics)
               type == TYPE_ENUM_FUNCTION);
 
   /* Grab an exclusive MDL lock. */
-  if (lock_routine_name(thd, type == TYPE_ENUM_FUNCTION,
-                        name->m_db.str, name->m_name.str))
+  if (lock_object_name(thd, mdl_type, name->m_db.str, name->m_name.str))
     DBUG_RETURN(SP_OPEN_TABLE_FAILED);
 
   if (!(table= open_proc_table_for_update(thd)))
@@ -1370,7 +1373,7 @@ sp_drop_db_routines(THD *thd, char *db)
   TABLE *table;
   int ret;
   uint key_len;
-  MDL_ticket *mdl_savepoint= thd->mdl_context.mdl_savepoint();
+  MDL_savepoint mdl_savepoint= thd->mdl_context.mdl_savepoint();
   DBUG_ENTER("sp_drop_db_routines");
   DBUG_PRINT("enter", ("db: %s", db));
 
@@ -1697,7 +1700,7 @@ bool sp_add_used_routine(Query_tables_list *prelocking_ctx, Query_arena *arena,
       (Sroutine_hash_entry *)arena->alloc(sizeof(Sroutine_hash_entry));
     if (!rn)              // OOM. Error will be reported using fatal_error().
       return FALSE;
-    rn->mdl_request.init(key, MDL_SHARED);
+    rn->mdl_request.init(key, MDL_SHARED, MDL_TRANSACTION);
     if (my_hash_insert(&prelocking_ctx->sroutines, (uchar *)rn))
       return FALSE;
     prelocking_ctx->sroutines_list.link_in_list(rn, &rn->next);
diff --git a/sql/sp_head.cc b/sql/sp_head.cc
index 0d33bd5c599..5089e7e0340 100644
--- a/sql/sp_head.cc
+++ b/sql/sp_head.cc
@@ -2140,6 +2140,8 @@ sp_head::execute_procedure(THD *thd, List<Item> *args)
 
     if (! thd->in_sub_stmt && ! thd->in_multi_stmt_transaction_mode())
       thd->mdl_context.release_transactional_locks();
+    else if (! thd->in_sub_stmt)
+      thd->mdl_context.release_statement_locks();
 
     thd->rollback_item_tree_changes();
 
@@ -2978,6 +2980,8 @@ sp_lex_keeper::reset_lex_and_exec_core(THD *thd, uint *nextp,
 
     if (! thd->in_sub_stmt && ! thd->in_multi_stmt_transaction_mode())
       thd->mdl_context.release_transactional_locks();
+    else if (! thd->in_sub_stmt)
+      thd->mdl_context.release_statement_locks();
   }
 
   if (m_lex->query_tables_own_last)
@@ -4176,7 +4180,8 @@ sp_head::add_used_tables_to_table_list(THD *thd,
       */
       table->mdl_request.init(MDL_key::TABLE, table->db, table->table_name,
                               table->lock_type >= TL_WRITE_ALLOW_WRITE ?
-                              MDL_SHARED_WRITE : MDL_SHARED_READ);
+                              MDL_SHARED_WRITE : MDL_SHARED_READ,
+                              MDL_TRANSACTION);
 
       /* Everyting else should be zeroed */
 
@@ -4220,7 +4225,7 @@ sp_add_to_query_tables(THD *thd, LEX *lex,
   table->select_lex= lex->current_select;
   table->cacheable_table= 1;
   table->mdl_request.init(MDL_key::TABLE, table->db, table->table_name,
-                          mdl_type);
+                          mdl_type, MDL_TRANSACTION);
 
   lex->add_to_query_tables(table);
   return table;
diff --git a/sql/sql_admin.cc b/sql/sql_admin.cc
index 21a05a5baca..f648d219fac 100644
--- a/sql/sql_admin.cc
+++ b/sql/sql_admin.cc
@@ -85,7 +85,7 @@ static int prepare_for_repair(THD *thd, TABLE_LIST *table_list,
     key_length= create_table_def_key(thd, key, table_list, 0);
     table_list->mdl_request.init(MDL_key::TABLE,
                                  table_list->db, table_list->table_name,
-                                 MDL_EXCLUSIVE);
+                                 MDL_EXCLUSIVE, MDL_TRANSACTION);
 
     if (lock_table_names(thd, table_list, table_list->next_global,
                          thd->variables.lock_wait_timeout,
diff --git a/sql/sql_base.cc b/sql/sql_base.cc
index 8caae3ee406..60c32a1a376 100644
--- a/sql/sql_base.cc
+++ b/sql/sql_base.cc
@@ -21,7 +21,7 @@
 #include "sql_priv.h"
 #include "unireg.h"
 #include "debug_sync.h"
-#include "lock.h"        // broadcast_refresh, mysql_lock_remove,
+#include "lock.h"        // mysql_lock_remove,
                          // mysql_unlock_tables,
                          // mysql_lock_have_duplicate
 #include "sql_show.h"    // append_identifier
@@ -1285,20 +1285,12 @@ static void mark_used_tables_as_free_for_reuse(THD *thd, TABLE *table)
 
 static void close_open_tables(THD *thd)
 {
-  bool found_old_table= 0;
-
   mysql_mutex_assert_not_owner(&LOCK_open);
 
   DBUG_PRINT("info", ("thd->open_tables: 0x%lx", (long) thd->open_tables));
 
   while (thd->open_tables)
-    found_old_table|= close_thread_table(thd, &thd->open_tables);
-
-  if (found_old_table)
-  {
-    /* Tell threads waiting for refresh that something has happened */
-    broadcast_refresh();
-  }
+    (void) close_thread_table(thd, &thd->open_tables);
 }
 
 
@@ -1364,11 +1356,6 @@ close_all_tables_for_name(THD *thd, TABLE_SHARE *share,
   /* Remove the table share from the cache. */
   tdc_remove_table(thd, TDC_RT_REMOVE_ALL, db, table_name,
                    FALSE);
-  /*
-    There could be a FLUSH thread waiting
-    on the table to go away. Wake it up.
-  */
-  broadcast_refresh();
 }
 
 
@@ -2463,7 +2450,8 @@ open_table_get_mdl_lock(THD *thd, Open_table_context *ot_ctx,
 
     mdl_request_shared.init(&mdl_request->key,
                             (flags & MYSQL_OPEN_FORCE_SHARED_MDL) ?
-                            MDL_SHARED : MDL_SHARED_HIGH_PRIO);
+                            MDL_SHARED : MDL_SHARED_HIGH_PRIO,
+                            MDL_TRANSACTION);
     mdl_request= &mdl_request_shared;
   }
 
@@ -2628,32 +2616,6 @@ bool open_table(THD *thd, TABLE_LIST *table_list, MEM_ROOT *mem_root,
                TMP_TABLE_KEY_EXTRA);
 
   /*
-    We need this to work for all tables, including temporary
-    tables, for backwards compatibility. But not under LOCK
-    TABLES, since under LOCK TABLES one can't use a non-prelocked
-    table.  This code only works for updates done inside DO/SELECT
-    f1() statements, normal DML is handled by means of
-    sql_command_flags.
-  */
-  if (global_read_lock && table_list->lock_type >= TL_WRITE_ALLOW_WRITE &&
-      ! (flags & MYSQL_OPEN_IGNORE_GLOBAL_READ_LOCK) &&
-      ! thd->locked_tables_mode)
-  {
-    /*
-      Someone has issued FLUSH TABLES WITH READ LOCK and we want
-      a write lock. Wait until the lock is gone.
-    */
-    if (thd->global_read_lock.wait_if_global_read_lock(thd, 1, 1))
-      DBUG_RETURN(TRUE);
-
-    if (thd->open_tables && thd->open_tables->s->version != refresh_version)
-    {
-      (void)ot_ctx->request_backoff_action(Open_table_context::OT_REOPEN_TABLES,
-                                           NULL);
-      DBUG_RETURN(TRUE);
-    }
-  }
-  /*
     Unless requested otherwise, try to resolve this table in the list
     of temporary tables of this thread. In MySQL temporary tables
     are always thread-local and "shadow" possible base tables with the
@@ -2824,6 +2786,59 @@ bool open_table(THD *thd, TABLE_LIST *table_list, MEM_ROOT *mem_root,
 
   if (! (flags & MYSQL_OPEN_HAS_MDL_LOCK))
   {
+    /*
+      We are not under LOCK TABLES and going to acquire write-lock/
+      modify the base table. We need to acquire protection against
+      global read lock until end of this statement in order to have
+      this statement blocked by active FLUSH TABLES WITH READ LOCK.
+
+      We don't block acquire this protection under LOCK TABLES as
+      such protection already acquired at LOCK TABLES time and
+      not released until UNLOCK TABLES.
+
+      We don't block statements which modify only temporary tables
+      as these tables are not preserved by backup by any form of
+      backup which uses FLUSH TABLES WITH READ LOCK.
+
+      TODO: The fact that we sometimes acquire protection against
+            GRL only when we encounter table to be write-locked
+            slightly increases probability of deadlock.
+            This problem will be solved once Alik pushes his
+            temporary table refactoring patch and we can start
+            pre-acquiring metadata locks at the beggining of
+            open_tables() call.
+    */
+    if (table_list->mdl_request.type >= MDL_SHARED_WRITE &&
+        ! (flags & (MYSQL_OPEN_IGNORE_GLOBAL_READ_LOCK |
+                    MYSQL_OPEN_FORCE_SHARED_MDL |
+                    MYSQL_OPEN_FORCE_SHARED_HIGH_PRIO_MDL |
+                    MYSQL_OPEN_SKIP_SCOPED_MDL_LOCK)) &&
+        ! ot_ctx->has_protection_against_grl())
+    {
+      MDL_request protection_request;
+      MDL_deadlock_handler mdl_deadlock_handler(ot_ctx);
+
+      if (thd->global_read_lock.can_acquire_protection())
+        DBUG_RETURN(TRUE);
+
+      protection_request.init(MDL_key::GLOBAL, "", "", MDL_INTENTION_EXCLUSIVE,
+                              MDL_STATEMENT);
+
+      /*
+        Install error handler which if possible will convert deadlock error
+        into request to back-off and restart process of opening tables.
+      */
+      thd->push_internal_handler(&mdl_deadlock_handler);
+      bool result= thd->mdl_context.acquire_lock(&protection_request,
+                                                 ot_ctx->get_timeout());
+      thd->pop_internal_handler();
+
+      if (result)
+        DBUG_RETURN(TRUE);
+
+      ot_ctx->set_has_protection_against_grl();
+    }
+
     if (open_table_get_mdl_lock(thd, ot_ctx, &table_list->mdl_request,
                                 flags, &mdl_ticket) ||
         mdl_ticket == NULL)
@@ -3379,7 +3394,6 @@ unlink_all_closed_tables(THD *thd, MYSQL_LOCK *lock, size_t reopen_count)
 
       close_thread_table(thd, &thd->open_tables);
     }
-    broadcast_refresh();
   }
   /* Exclude all closed tables from the LOCK TABLES list. */
   for (TABLE_LIST *table_list= m_locked_tables; table_list; table_list=
@@ -3856,7 +3870,8 @@ Open_table_context::Open_table_context(THD *thd, uint flags)
              LONG_TIMEOUT : thd->variables.lock_wait_timeout),
    m_flags(flags),
    m_action(OT_NO_ACTION),
-   m_has_locks(thd->mdl_context.has_locks())
+   m_has_locks(thd->mdl_context.has_locks()),
+   m_has_protection_against_grl(FALSE)
 {}
 
 
@@ -4013,6 +4028,12 @@ recover_from_failed_open(THD *thd)
     for safety.
   */
   m_failed_table= NULL;
+  /*
+    Reset flag indicating that we have already acquired protection
+    against GRL. It is no longer valid as the corresponding lock was
+    released by close_tables_for_reopen().
+  */
+  m_has_protection_against_grl= FALSE;
   /* Prepare for possible another back-off. */
   m_action= OT_NO_ACTION;
   return result;
@@ -4551,11 +4572,20 @@ lock_table_names(THD *thd,
       if (schema_request == NULL)
         return TRUE;
       schema_request->init(MDL_key::SCHEMA, table->db, "",
-                           MDL_INTENTION_EXCLUSIVE);
+                           MDL_INTENTION_EXCLUSIVE,
+                           MDL_TRANSACTION);
       mdl_requests.push_front(schema_request);
     }
-    /* Take the global intention exclusive lock. */
-    global_request.init(MDL_key::GLOBAL, "", "", MDL_INTENTION_EXCLUSIVE);
+
+    /*
+      Protect this statement against concurrent global read lock
+      by acquiring global intention exclusive lock with statement
+      duration.
+    */
+    if (thd->global_read_lock.can_acquire_protection())
+      return TRUE;
+    global_request.init(MDL_key::GLOBAL, "", "", MDL_INTENTION_EXCLUSIVE,
+                        MDL_STATEMENT);
     mdl_requests.push_front(&global_request);
   }
 
@@ -5362,7 +5392,7 @@ bool open_and_lock_tables(THD *thd, TABLE_LIST *tables,
                           Prelocking_strategy *prelocking_strategy)
 {
   uint counter;
-  MDL_ticket *mdl_savepoint= thd->mdl_context.mdl_savepoint();
+  MDL_savepoint mdl_savepoint= thd->mdl_context.mdl_savepoint();
   DBUG_ENTER("open_and_lock_tables");
   DBUG_PRINT("enter", ("derived handling: %d", derived));
 
@@ -5419,7 +5449,7 @@ bool open_normal_and_derived_tables(THD *thd, TABLE_LIST *tables, uint flags)
 {
   DML_prelocking_strategy prelocking_strategy;
   uint counter;
-  MDL_ticket *mdl_savepoint= thd->mdl_context.mdl_savepoint();
+  MDL_savepoint mdl_savepoint= thd->mdl_context.mdl_savepoint();
   DBUG_ENTER("open_normal_and_derived_tables");
   DBUG_ASSERT(!thd->fill_derived_tables());
   if (open_tables(thd, &tables, &counter, flags, &prelocking_strategy) ||
@@ -5676,7 +5706,7 @@ bool lock_tables(THD *thd, TABLE_LIST *tables, uint count,
 */
 
 void close_tables_for_reopen(THD *thd, TABLE_LIST **tables,
-                             MDL_ticket *start_of_statement_svp)
+                             const MDL_savepoint &start_of_statement_svp)
 {
   TABLE_LIST *first_not_own_table= thd->lex->first_not_own_table();
   TABLE_LIST *tmp;
diff --git a/sql/sql_base.h b/sql/sql_base.h
index 00f335ab209..35fa04b3674 100644
--- a/sql/sql_base.h
+++ b/sql/sql_base.h
@@ -159,7 +159,7 @@ thr_lock_type read_lock_type_for_table(THD *thd,
 my_bool mysql_rm_tmp_tables(void);
 bool rm_temporary_table(handlerton *base, char *path);
 void close_tables_for_reopen(THD *thd, TABLE_LIST **tables,
-                             MDL_ticket *start_of_statement_svp);
+                             const MDL_savepoint &start_of_statement_svp);
 TABLE_LIST *find_table_in_list(TABLE_LIST *table,
                                TABLE_LIST *TABLE_LIST::*link,
                                const char *db_name,
@@ -507,7 +507,7 @@ public:
     the statement, so that we can rollback to it before waiting on
     locks.
   */
-  MDL_ticket *start_of_statement_svp() const
+  const MDL_savepoint &start_of_statement_svp() const
   {
     return m_start_of_statement_svp;
   }
@@ -518,6 +518,21 @@ public:
   }
 
   uint get_flags() const { return m_flags; }
+
+  /**
+    Set flag indicating that we have already acquired metadata lock
+    protecting this statement against GRL while opening tables.
+  */
+  void set_has_protection_against_grl()
+  {
+    m_has_protection_against_grl= TRUE;
+  }
+
+  bool has_protection_against_grl() const
+  {
+    return m_has_protection_against_grl;
+  }
+
 private:
   /**
     For OT_DISCOVER and OT_REPAIR actions, the table list element for
@@ -525,7 +540,7 @@ private:
     should be repaired.
   */
   TABLE_LIST *m_failed_table;
-  MDL_ticket *m_start_of_statement_svp;
+  MDL_savepoint m_start_of_statement_svp;
   /**
     Lock timeout in seconds. Initialized to LONG_TIMEOUT when opening system
     tables or to the "lock_wait_timeout" system variable for regular tables.
@@ -541,6 +556,11 @@ private:
     and we can't safely do back-off (and release them).
   */
   bool m_has_locks;
+  /**
+    Indicates that in the process of opening tables we have acquired
+    protection against global read lock.
+  */
+  bool m_has_protection_against_grl;
 };
 
 
diff --git a/sql/sql_class.cc b/sql/sql_class.cc
index c848d686299..1823a0416ff 100644
--- a/sql/sql_class.cc
+++ b/sql/sql_class.cc
@@ -3497,11 +3497,15 @@ void THD::set_mysys_var(struct st_my_thread_var *new_mysys_var)
 void THD::leave_locked_tables_mode()
 {
   locked_tables_mode= LTM_NONE;
-  /* Make sure we don't release the global read lock when leaving LTM. */
-  mdl_context.reset_trans_sentinel(global_read_lock.global_shared_lock());
+  mdl_context.set_transaction_duration_for_all_locks();
+  /*
+    Make sure we don't release the global read lock and commit blocker
+    when leaving LTM.
+  */
+  global_read_lock.set_explicit_lock_duration(this);
   /* Also ensure that we don't release metadata locks for open HANDLERs. */
   if (handler_tables_hash.records)
-    mysql_ha_move_tickets_after_trans_sentinel(this);
+    mysql_ha_set_explicit_lock_duration(this);
 }
 
 void THD::get_definer(LEX_USER *definer)
diff --git a/sql/sql_class.h b/sql/sql_class.h
index 8c444f34364..8bf72f1cdb2 100644
--- a/sql/sql_class.h
+++ b/sql/sql_class.h
@@ -822,8 +822,8 @@ struct st_savepoint {
   char                *name;
   uint                 length;
   Ha_trx_info         *ha_list;
-  /** Last acquired lock before this savepoint was set. */
-  MDL_ticket     *mdl_savepoint;
+  /** State of metadata locks before this savepoint was set. */
+  MDL_savepoint        mdl_savepoint;
 };
 
 enum xa_states {XA_NOTR=0, XA_ACTIVE, XA_IDLE, XA_PREPARED, XA_ROLLBACK_ONLY};
@@ -1058,12 +1058,12 @@ class Open_tables_backup: public Open_tables_state
 public:
   /**
     When we backup the open tables state to open a system
-    table or tables, points at the last metadata lock
-    acquired before the backup. Is used to release
-    metadata locks on system tables after they are
+    table or tables, we want to save state of metadata
+    locks which were acquired before the backup. It is used
+    to release metadata locks on system tables after they are
     no longer used.
   */
-  MDL_ticket *mdl_system_tables_svp;
+  MDL_savepoint mdl_system_tables_svp;
 };
 
 /**
@@ -1336,26 +1336,43 @@ public:
   };
 
   Global_read_lock()
-    :m_protection_count(0), m_state(GRL_NONE), m_mdl_global_shared_lock(NULL)
+    : m_state(GRL_NONE),
+      m_mdl_global_shared_lock(NULL),
+      m_mdl_blocks_commits_lock(NULL)
   {}
 
   bool lock_global_read_lock(THD *thd);
   void unlock_global_read_lock(THD *thd);
-  bool wait_if_global_read_lock(THD *thd, bool abort_on_refresh,
-                                bool is_not_commit);
-  void start_waiting_global_read_lock(THD *thd);
+  /**
+    Check if this connection can acquire protection against GRL and
+    emit error if otherwise.
+  */
+  bool can_acquire_protection() const
+  {
+    if (m_state)
+    {
+      my_error(ER_CANT_UPDATE_WITH_READLOCK, MYF(0));
+      return TRUE;
+    }
+    return FALSE;
+  }
   bool make_global_read_lock_block_commit(THD *thd);
   bool is_acquired() const { return m_state != GRL_NONE; }
-  bool has_protection() const { return m_protection_count > 0; }
-  MDL_ticket *global_shared_lock() const { return m_mdl_global_shared_lock; }
+  void set_explicit_lock_duration(THD *thd);
 private:
-  uint           m_protection_count;            // GRL protection count
+  enum_grl_state m_state;
   /**
     In order to acquire the global read lock, the connection must
-    acquire a global shared metadata lock, to prohibit all DDL.
+    acquire shared metadata lock in GLOBAL namespace, to prohibit
+    all DDL.
   */
-  enum_grl_state m_state;
   MDL_ticket *m_mdl_global_shared_lock;
+  /**
+    Also in order to acquire the global read lock, the connection
+    must acquire a shared metadata lock in COMMIT namespace, to
+    prohibit commits.
+  */
+  MDL_ticket *m_mdl_blocks_commits_lock;
 };
 
 
@@ -2697,7 +2714,7 @@ public:
   {
     DBUG_ASSERT(locked_tables_mode == LTM_NONE);
 
-    mdl_context.set_trans_sentinel();
+    mdl_context.set_explicit_duration_for_all_locks();
     locked_tables_mode= mode_arg;
   }
   void leave_locked_tables_mode();
@@ -3503,20 +3520,10 @@ public:
 #define CF_DIAGNOSTIC_STMT        (1U << 8)
 
 /**
-  SQL statements that must be protected against impending global read lock
-  to prevent deadlock. This deadlock could otherwise happen if the statement
-  starts waiting for the GRL to go away inside mysql_lock_tables while at the
-  same time having "old" opened tables. The thread holding the GRL can be
-  waiting for these "old" opened tables to be closed, causing a deadlock
-  (FLUSH TABLES WITH READ LOCK).
- */
-#define CF_PROTECT_AGAINST_GRL  (1U << 10)
-
-/**
   Identifies statements that may generate row events
   and that may end up in the binary log.
 */
-#define CF_CAN_GENERATE_ROW_EVENTS (1U << 11)
+#define CF_CAN_GENERATE_ROW_EVENTS (1U << 9)
 
 /* Bits in server_command_flags */
 
diff --git a/sql/sql_db.cc b/sql/sql_db.cc
index 517cb9139e9..4df8748429c 100644
--- a/sql/sql_db.cc
+++ b/sql/sql_db.cc
@@ -1054,7 +1054,8 @@ static long mysql_rm_known_files(THD *thd, MY_DIR *dirp, const char *db,
       table_list->alias= table_list->table_name;	// If lower_case_table_names=2
       table_list->internal_tmp_table= is_prefix(file->name, tmp_file_prefix);
       table_list->mdl_request.init(MDL_key::TABLE, table_list->db,
-                                   table_list->table_name, MDL_EXCLUSIVE);
+                                   table_list->table_name, MDL_EXCLUSIVE,
+                                   MDL_TRANSACTION);
       /* Link into list */
       (*tot_list_next_local)= table_list;
       (*tot_list_next_global)= table_list;
diff --git a/sql/sql_handler.cc b/sql/sql_handler.cc
index a5c126a8521..b5cd3ac9e9a 100644
--- a/sql/sql_handler.cc
+++ b/sql/sql_handler.cc
@@ -55,7 +55,7 @@
 #include "sql_handler.h"
 #include "unireg.h"                    // REQUIRED: for other includes
 #include "sql_base.h"                           // close_thread_tables
-#include "lock.h"            // broadcast_refresh, mysql_unlock_tables
+#include "lock.h"                               // mysql_unlock_tables
 #include "key.h"                                // key_copy
 #include "sql_base.h"                           // insert_fields
 #include "sql_select.h"
@@ -131,11 +131,7 @@ static void mysql_ha_close_table(THD *thd, TABLE_LIST *tables)
     /* Non temporary table. */
     tables->table->file->ha_index_or_rnd_end();
     tables->table->open_by_handler= 0;
-    if (close_thread_table(thd, &tables->table))
-    {
-      /* Tell threads waiting for refresh that something has happened */
-      broadcast_refresh();
-    }
+    (void) close_thread_table(thd, &tables->table);
     thd->mdl_context.release_lock(tables->mdl_request.ticket);
   }
   else if (tables->table)
@@ -183,7 +179,7 @@ bool mysql_ha_open(THD *thd, TABLE_LIST *tables, bool reopen)
   uint          dblen, namelen, aliaslen, counter;
   bool          error;
   TABLE         *backup_open_tables;
-  MDL_ticket    *mdl_savepoint;
+  MDL_savepoint mdl_savepoint;
   DBUG_ENTER("mysql_ha_open");
   DBUG_PRINT("enter",("'%s'.'%s' as '%s'  reopen: %d",
                       tables->db, tables->table_name, tables->alias,
@@ -252,7 +248,13 @@ bool mysql_ha_open(THD *thd, TABLE_LIST *tables, bool reopen)
     memcpy(hash_tables->db, tables->db, dblen);
     memcpy(hash_tables->table_name, tables->table_name, namelen);
     memcpy(hash_tables->alias, tables->alias, aliaslen);
-    hash_tables->mdl_request.init(MDL_key::TABLE, db, name, MDL_SHARED);
+    /*
+      We can't request lock with explicit duration for this table
+      right from the start as open_tables() can't handle properly
+      back-off for such locks.
+    */
+    hash_tables->mdl_request.init(MDL_key::TABLE, db, name, MDL_SHARED,
+                                  MDL_TRANSACTION);
     /* for now HANDLER can be used only for real TABLES */
     hash_tables->required_type= FRMTYPE_TABLE;
 
@@ -332,8 +334,8 @@ bool mysql_ha_open(THD *thd, TABLE_LIST *tables, bool reopen)
   thd->set_open_tables(backup_open_tables);
   if (hash_tables->mdl_request.ticket)
   {
-    thd->mdl_context.
-      move_ticket_after_trans_sentinel(hash_tables->mdl_request.ticket);
+    thd->mdl_context.set_lock_duration(hash_tables->mdl_request.ticket,
+                                       MDL_EXPLICIT);
     thd->mdl_context.set_needs_thr_lock_abort(TRUE);
   }
 
@@ -969,24 +971,23 @@ void mysql_ha_cleanup(THD *thd)
 
 
 /**
-  Move tickets for metadata locks corresponding to open HANDLERs
-  after transaction sentinel in order to protect them from being
-  released at the end of transaction.
+  Set explicit duration for metadata locks corresponding to open HANDLERs
+  to protect them from being released at the end of transaction.
 
   @param thd Thread identifier.
 */
 
-void mysql_ha_move_tickets_after_trans_sentinel(THD *thd)
+void mysql_ha_set_explicit_lock_duration(THD *thd)
 {
   TABLE_LIST *hash_tables;
-  DBUG_ENTER("mysql_ha_move_tickets_after_trans_sentinel");
+  DBUG_ENTER("mysql_ha_set_explicit_lock_duration");
 
   for (uint i= 0; i < thd->handler_tables_hash.records; i++)
   {
     hash_tables= (TABLE_LIST*) my_hash_element(&thd->handler_tables_hash, i);
     if (hash_tables->table && hash_tables->table->mdl_ticket)
-      thd->mdl_context.
-             move_ticket_after_trans_sentinel(hash_tables->table->mdl_ticket);
+      thd->mdl_context.set_lock_duration(hash_tables->table->mdl_ticket,
+                                         MDL_EXPLICIT);
   }
   DBUG_VOID_RETURN;
 }
diff --git a/sql/sql_handler.h b/sql/sql_handler.h
index c5da3c4d468..2eea552d7c9 100644
--- a/sql/sql_handler.h
+++ b/sql/sql_handler.h
@@ -31,6 +31,6 @@ void mysql_ha_flush(THD *thd);
 void mysql_ha_flush_tables(THD *thd, TABLE_LIST *all_tables);
 void mysql_ha_rm_tables(THD *thd, TABLE_LIST *tables);
 void mysql_ha_cleanup(THD *thd);
-void mysql_ha_move_tickets_after_trans_sentinel(THD *thd);
+void mysql_ha_set_explicit_lock_duration(THD *thd);
 
 #endif /* SQL_HANDLER_INCLUDED */
diff --git a/sql/sql_insert.cc b/sql/sql_insert.cc
index 1f8da3fab5c..860a5b8941a 100644
--- a/sql/sql_insert.cc
+++ b/sql/sql_insert.cc
@@ -77,7 +77,8 @@
 #include "sql_audit.h"
 
 #ifndef EMBEDDED_LIBRARY
-static bool delayed_get_table(THD *thd, TABLE_LIST *table_list);
+static bool delayed_get_table(THD *thd, MDL_request *grl_protection_request,
+                              TABLE_LIST *table_list);
 static int write_delayed(THD *thd, TABLE *table, enum_duplicates duplic,
                          LEX_STRING query, bool ignore, bool log_on);
 static void end_delayed_insert(THD *thd);
@@ -529,32 +530,28 @@ void upgrade_lock_type(THD *thd, thr_lock_type *lock_type,
 static
 bool open_and_lock_for_insert_delayed(THD *thd, TABLE_LIST *table_list)
 {
+  MDL_request protection_request;
   DBUG_ENTER("open_and_lock_for_insert_delayed");
 
 #ifndef EMBEDDED_LIBRARY
-  if (thd->locked_tables_mode && thd->global_read_lock.is_acquired())
-  {
-    /*
-      If this connection has the global read lock, the handler thread
-      will not be able to lock the table. It will wait for the global
-      read lock to go away, but this will never happen since the
-      connection thread will be stuck waiting for the handler thread
-      to open and lock the table.
-      If we are not in locked tables mode, INSERT will seek protection
-      against the global read lock (and fail), thus we will only get
-      to this point in locked tables mode.
-    */
-    my_error(ER_CANT_UPDATE_WITH_READLOCK, MYF(0));
-    DBUG_RETURN(TRUE);
-  }
-
   /*
     In order for the deadlock detector to be able to find any deadlocks
-    caused by the handler thread locking this table, we take the metadata
-    lock inside the connection thread. If this goes ok, the ticket is cloned
-    and added to the list of granted locks held by the handler thread.
+    caused by the handler thread waiting for GRL or this table, we acquire
+    protection against GRL (global IX metadata lock) and metadata lock on
+    table to being inserted into inside the connection thread.
+    If this goes ok, the tickets are cloned and added to the list of granted
+    locks held by the handler thread.
   */
-  MDL_ticket *mdl_savepoint= thd->mdl_context.mdl_savepoint();
+  if (thd->global_read_lock.can_acquire_protection())
+    DBUG_RETURN(TRUE);
+
+  protection_request.init(MDL_key::GLOBAL, "", "", MDL_INTENTION_EXCLUSIVE,
+                          MDL_STATEMENT);
+
+  if (thd->mdl_context.acquire_lock(&protection_request,
+                                    thd->variables.lock_wait_timeout))
+    DBUG_RETURN(TRUE);
+
   if (thd->mdl_context.acquire_lock(&table_list->mdl_request,
                                     thd->variables.lock_wait_timeout))
     /*
@@ -564,7 +561,7 @@ bool open_and_lock_for_insert_delayed(THD *thd, TABLE_LIST *table_list)
     DBUG_RETURN(TRUE);
 
   bool error= FALSE;
-  if (delayed_get_table(thd, table_list))
+  if (delayed_get_table(thd, &protection_request, table_list))
     error= TRUE;
   else if (table_list->table)
   {
@@ -589,13 +586,13 @@ bool open_and_lock_for_insert_delayed(THD *thd, TABLE_LIST *table_list)
   }
 
   /*
-    If a lock was acquired above, we should release it after
-    handle_delayed_insert() has cloned the ticket. Note that acquire_lock() can
-    succeed because the connection already has the lock. In this case the ticket
-    will be before the mdl_savepoint and we should not release it here.
+    We can't release protection against GRL and metadata lock on the table
+    being inserted into here. These locks might be required, for example,
+    because this INSERT DELAYED calls functions which may try to update
+    this or another tables (updating the same table is of course illegal,
+    but such an attempt can be discovered only later during statement
+    execution).
   */
-  if (!thd->mdl_context.has_lock(mdl_savepoint, table_list->mdl_request.ticket))
-    thd->mdl_context.release_lock(table_list->mdl_request.ticket);
 
   /*
     Reset the ticket in case we end up having to use normal insert and
@@ -1873,10 +1870,11 @@ public:
   mysql_cond_t cond, cond_client;
   volatile uint tables_in_use,stacked_inserts;
   volatile bool status;
-  /*
+  /**
     When the handler thread starts, it clones a metadata lock ticket
-    for the table to be inserted. This is done to allow the deadlock
-    detector to detect deadlocks resulting from this lock.
+    which protects against GRL and ticket for the table to be inserted.
+    This is done to allow the deadlock detector to detect deadlocks
+    resulting from these locks.
     Before this is done, the connection thread cannot safely exit
     without causing problems for clone_ticket().
     Once handler_thread_initialized has been set, it is safe for the
@@ -1888,6 +1886,11 @@ public:
   I_List<delayed_row> rows;
   ulong group_count;
   TABLE_LIST table_list;			// Argument
+  /**
+    Request for IX metadata lock protecting against GRL which is
+    passed from connection thread to the handler thread.
+  */
+  MDL_request grl_protection;
 
   Delayed_insert()
     :locks_in_memory(0), table(0),tables_in_use(0),stacked_inserts(0),
@@ -2066,7 +2069,8 @@ Delayed_insert *find_handler(THD *thd, TABLE_LIST *table_list)
 */
 
 static
-bool delayed_get_table(THD *thd, TABLE_LIST *table_list)
+bool delayed_get_table(THD *thd, MDL_request *grl_protection_request,
+                       TABLE_LIST *table_list)
 {
   int error;
   Delayed_insert *di;
@@ -2110,7 +2114,10 @@ bool delayed_get_table(THD *thd, TABLE_LIST *table_list)
       /* Replace volatile strings with local copies */
       di->table_list.alias= di->table_list.table_name= di->thd.query();
       di->table_list.db= di->thd.db;
-      /* We need the ticket so that it can be cloned in handle_delayed_insert */
+      /* We need the tickets so that they can be cloned in handle_delayed_insert */
+      di->grl_protection.init(MDL_key::GLOBAL, "", "",
+                              MDL_INTENTION_EXCLUSIVE, MDL_STATEMENT);
+      di->grl_protection.ticket= grl_protection_request->ticket;
       init_mdl_requests(&di->table_list);
       di->table_list.mdl_request.ticket= table_list->mdl_request.ticket;
 
@@ -2650,13 +2657,15 @@ pthread_handler_t handle_delayed_insert(void *arg)
     thd->set_current_stmt_binlog_format_row_if_mixed();
 
     /*
-      Clone the ticket representing the lock on the target table for
-      the insert and add it to the list of granted metadata locks held by
-      the handler thread. This is safe since the handler thread is
-      not holding nor waiting on any metadata locks.
+      Clone tickets representing protection against GRL and the lock on
+      the target table for the insert and add them to the list of granted
+      metadata locks held by the handler thread. This is safe since the
+      handler thread is not holding nor waiting on any metadata locks.
     */
-    if (thd->mdl_context.clone_ticket(&di->table_list.mdl_request))
+    if (thd->mdl_context.clone_ticket(&di->grl_protection) ||
+        thd->mdl_context.clone_ticket(&di->table_list.mdl_request))
     {
+      thd->mdl_context.release_transactional_locks();
       di->handler_thread_initialized= TRUE;
       goto err;
     }
diff --git a/sql/sql_lex.cc b/sql/sql_lex.cc
index d91489b4a7a..7a8a86d3ca4 100644
--- a/sql/sql_lex.cc
+++ b/sql/sql_lex.cc
@@ -417,7 +417,6 @@ void lex_start(THD *thd)
   lex->nest_level=0 ;
   lex->allow_sum_func= 0;
   lex->in_sum_func= NULL;
-  lex->protect_against_global_read_lock= FALSE;
   /*
     ok, there must be a better solution for this, long-term
     I tried "bzero" in the sql_yacc.yy code, but that for
diff --git a/sql/sql_lex.h b/sql/sql_lex.h
index c20c2f0bca2..191562bd3e8 100644
--- a/sql/sql_lex.h
+++ b/sql/sql_lex.h
@@ -2394,22 +2394,6 @@ struct LEX: public Query_tables_list
   bool escape_used;
   bool is_lex_started; /* If lex_start() did run. For debugging. */
 
-  /*
-    Special case for SELECT .. FOR UPDATE and LOCK TABLES .. WRITE.
-
-    Protect from a impending GRL as otherwise the thread might deadlock
-    if it starts waiting for the GRL in mysql_lock_tables.
-
-    The protection is needed because there is a race between setting
-    the global read lock and waiting for all open tables to be closed.
-    The problem is a circular wait where a thread holding "old" open
-    tables will wait for the global read lock to be released while the
-    thread holding the global read lock will wait for all "old" open
-    tables to be closed -- the flush part of flush tables with read
-    lock.
-  */
-  bool protect_against_global_read_lock;
-
   LEX();
 
   virtual ~LEX()
diff --git a/sql/sql_parse.cc b/sql/sql_parse.cc
index c09a4abb2c8..e95745634e8 100644
--- a/sql/sql_parse.cc
+++ b/sql/sql_parse.cc
@@ -18,12 +18,9 @@
 #include "sql_priv.h"
 #include "unireg.h"                    // REQUIRED: for other includes
 #include "sql_parse.h"        // sql_kill, *_precheck, *_prepare
-#include "lock.h"             // wait_if_global_read_lock,
-                              // unlock_global_read_lock,
-                              // try_transactional_lock,
+#include "lock.h"             // try_transactional_lock,
                               // check_transactional_lock,
                               // set_handler_table_locks,
-                              // start_waiting_global_read_lock,
                               // lock_global_read_lock,
                               // make_global_read_lock_block_commit
 #include "sql_base.h"         // find_temporary_tablesx
@@ -260,21 +257,20 @@ void init_update_queries(void)
     the code, in particular in the Query_log_event's constructor.
   */
   sql_command_flags[SQLCOM_CREATE_TABLE]=   CF_CHANGES_DATA | CF_REEXECUTION_FRAGILE |
-                                            CF_AUTO_COMMIT_TRANS | CF_PROTECT_AGAINST_GRL |
+                                            CF_AUTO_COMMIT_TRANS |
                                             CF_CAN_GENERATE_ROW_EVENTS;
   sql_command_flags[SQLCOM_CREATE_INDEX]=   CF_CHANGES_DATA | CF_AUTO_COMMIT_TRANS;
   sql_command_flags[SQLCOM_ALTER_TABLE]=    CF_CHANGES_DATA | CF_WRITE_LOGS_COMMAND |
-                                            CF_AUTO_COMMIT_TRANS | CF_PROTECT_AGAINST_GRL;
+                                            CF_AUTO_COMMIT_TRANS;
   sql_command_flags[SQLCOM_TRUNCATE]=       CF_CHANGES_DATA | CF_WRITE_LOGS_COMMAND |
-                                            CF_AUTO_COMMIT_TRANS | CF_PROTECT_AGAINST_GRL;
+                                            CF_AUTO_COMMIT_TRANS;
   sql_command_flags[SQLCOM_DROP_TABLE]=     CF_CHANGES_DATA | CF_AUTO_COMMIT_TRANS;
   sql_command_flags[SQLCOM_LOAD]=           CF_CHANGES_DATA | CF_REEXECUTION_FRAGILE |
-                                            CF_PROTECT_AGAINST_GRL |
                                             CF_CAN_GENERATE_ROW_EVENTS;
-  sql_command_flags[SQLCOM_CREATE_DB]=      CF_CHANGES_DATA | CF_AUTO_COMMIT_TRANS | CF_PROTECT_AGAINST_GRL;
-  sql_command_flags[SQLCOM_DROP_DB]=        CF_CHANGES_DATA | CF_AUTO_COMMIT_TRANS | CF_PROTECT_AGAINST_GRL;
-  sql_command_flags[SQLCOM_ALTER_DB_UPGRADE]= CF_AUTO_COMMIT_TRANS | CF_PROTECT_AGAINST_GRL;
-  sql_command_flags[SQLCOM_ALTER_DB]=       CF_CHANGES_DATA | CF_AUTO_COMMIT_TRANS | CF_PROTECT_AGAINST_GRL;
+  sql_command_flags[SQLCOM_CREATE_DB]=      CF_CHANGES_DATA | CF_AUTO_COMMIT_TRANS;
+  sql_command_flags[SQLCOM_DROP_DB]=        CF_CHANGES_DATA | CF_AUTO_COMMIT_TRANS;
+  sql_command_flags[SQLCOM_ALTER_DB_UPGRADE]= CF_AUTO_COMMIT_TRANS;
+  sql_command_flags[SQLCOM_ALTER_DB]=       CF_CHANGES_DATA | CF_AUTO_COMMIT_TRANS;
   sql_command_flags[SQLCOM_RENAME_TABLE]=   CF_CHANGES_DATA | CF_AUTO_COMMIT_TRANS;
   sql_command_flags[SQLCOM_DROP_INDEX]=     CF_CHANGES_DATA | CF_AUTO_COMMIT_TRANS;
   sql_command_flags[SQLCOM_CREATE_VIEW]=    CF_CHANGES_DATA | CF_REEXECUTION_FRAGILE |
@@ -285,26 +281,18 @@ void init_update_queries(void)
   sql_command_flags[SQLCOM_CREATE_EVENT]=   CF_CHANGES_DATA | CF_AUTO_COMMIT_TRANS;
   sql_command_flags[SQLCOM_ALTER_EVENT]=    CF_CHANGES_DATA | CF_AUTO_COMMIT_TRANS;
   sql_command_flags[SQLCOM_DROP_EVENT]=     CF_CHANGES_DATA | CF_AUTO_COMMIT_TRANS;
-  sql_command_flags[SQLCOM_CREATE_TRIGGER]= CF_AUTO_COMMIT_TRANS;
-  sql_command_flags[SQLCOM_DROP_TRIGGER]=   CF_AUTO_COMMIT_TRANS;
 
   sql_command_flags[SQLCOM_UPDATE]=	    CF_CHANGES_DATA | CF_REEXECUTION_FRAGILE |
-                                            CF_PROTECT_AGAINST_GRL |
                                             CF_CAN_GENERATE_ROW_EVENTS;
   sql_command_flags[SQLCOM_UPDATE_MULTI]=   CF_CHANGES_DATA | CF_REEXECUTION_FRAGILE |
-                                            CF_PROTECT_AGAINST_GRL |
                                             CF_CAN_GENERATE_ROW_EVENTS;
   sql_command_flags[SQLCOM_INSERT]=	    CF_CHANGES_DATA | CF_REEXECUTION_FRAGILE |
-                                            CF_PROTECT_AGAINST_GRL |
                                             CF_CAN_GENERATE_ROW_EVENTS;
   sql_command_flags[SQLCOM_INSERT_SELECT]=  CF_CHANGES_DATA | CF_REEXECUTION_FRAGILE |
-                                            CF_PROTECT_AGAINST_GRL |
                                             CF_CAN_GENERATE_ROW_EVENTS;
   sql_command_flags[SQLCOM_DELETE]=         CF_CHANGES_DATA | CF_REEXECUTION_FRAGILE |
-                                            CF_PROTECT_AGAINST_GRL |
                                             CF_CAN_GENERATE_ROW_EVENTS;
   sql_command_flags[SQLCOM_DELETE_MULTI]=   CF_CHANGES_DATA | CF_REEXECUTION_FRAGILE |
-                                            CF_PROTECT_AGAINST_GRL |
                                             CF_CAN_GENERATE_ROW_EVENTS;
   sql_command_flags[SQLCOM_REPLACE]=        CF_CHANGES_DATA | CF_REEXECUTION_FRAGILE |
                                             CF_CAN_GENERATE_ROW_EVENTS;
@@ -366,20 +354,19 @@ void init_update_queries(void)
                                                 CF_REEXECUTION_FRAGILE);
 
 
-  sql_command_flags[SQLCOM_CREATE_USER]=       CF_CHANGES_DATA | CF_PROTECT_AGAINST_GRL;
-  sql_command_flags[SQLCOM_RENAME_USER]=       CF_CHANGES_DATA | CF_PROTECT_AGAINST_GRL;
-  sql_command_flags[SQLCOM_DROP_USER]=         CF_CHANGES_DATA | CF_PROTECT_AGAINST_GRL;
+  sql_command_flags[SQLCOM_CREATE_USER]=       CF_CHANGES_DATA;
+  sql_command_flags[SQLCOM_RENAME_USER]=       CF_CHANGES_DATA;
+  sql_command_flags[SQLCOM_DROP_USER]=         CF_CHANGES_DATA;
   sql_command_flags[SQLCOM_GRANT]=             CF_CHANGES_DATA;
   sql_command_flags[SQLCOM_REVOKE]=            CF_CHANGES_DATA;
-  sql_command_flags[SQLCOM_REVOKE_ALL]=        CF_PROTECT_AGAINST_GRL;
   sql_command_flags[SQLCOM_OPTIMIZE]=          CF_CHANGES_DATA;
   sql_command_flags[SQLCOM_CREATE_FUNCTION]=   CF_CHANGES_DATA;
-  sql_command_flags[SQLCOM_CREATE_PROCEDURE]=  CF_CHANGES_DATA | CF_PROTECT_AGAINST_GRL | CF_AUTO_COMMIT_TRANS;
-  sql_command_flags[SQLCOM_CREATE_SPFUNCTION]= CF_CHANGES_DATA | CF_PROTECT_AGAINST_GRL | CF_AUTO_COMMIT_TRANS;
-  sql_command_flags[SQLCOM_DROP_PROCEDURE]=    CF_CHANGES_DATA | CF_PROTECT_AGAINST_GRL | CF_AUTO_COMMIT_TRANS;
-  sql_command_flags[SQLCOM_DROP_FUNCTION]=     CF_CHANGES_DATA | CF_PROTECT_AGAINST_GRL | CF_AUTO_COMMIT_TRANS;
-  sql_command_flags[SQLCOM_ALTER_PROCEDURE]=   CF_CHANGES_DATA | CF_PROTECT_AGAINST_GRL | CF_AUTO_COMMIT_TRANS;
-  sql_command_flags[SQLCOM_ALTER_FUNCTION]=    CF_CHANGES_DATA | CF_PROTECT_AGAINST_GRL | CF_AUTO_COMMIT_TRANS;
+  sql_command_flags[SQLCOM_CREATE_PROCEDURE]=  CF_CHANGES_DATA | CF_AUTO_COMMIT_TRANS;
+  sql_command_flags[SQLCOM_CREATE_SPFUNCTION]= CF_CHANGES_DATA | CF_AUTO_COMMIT_TRANS;
+  sql_command_flags[SQLCOM_DROP_PROCEDURE]=    CF_CHANGES_DATA | CF_AUTO_COMMIT_TRANS;
+  sql_command_flags[SQLCOM_DROP_FUNCTION]=     CF_CHANGES_DATA | CF_AUTO_COMMIT_TRANS;
+  sql_command_flags[SQLCOM_ALTER_PROCEDURE]=   CF_CHANGES_DATA | CF_AUTO_COMMIT_TRANS;
+  sql_command_flags[SQLCOM_ALTER_FUNCTION]=    CF_CHANGES_DATA | CF_AUTO_COMMIT_TRANS;
   sql_command_flags[SQLCOM_INSTALL_PLUGIN]=    CF_CHANGES_DATA;
   sql_command_flags[SQLCOM_UNINSTALL_PLUGIN]=  CF_CHANGES_DATA;
 
@@ -1111,7 +1098,7 @@ bool dispatch_command(enum enum_server_command command, THD *thd,
       SHOW statements should not add the used tables to the list of tables
       used in a transaction.
     */
-    MDL_ticket *mdl_savepoint= thd->mdl_context.mdl_savepoint();
+    MDL_savepoint mdl_savepoint= thd->mdl_context.mdl_savepoint();
 
     status_var_increment(thd->status_var.com_stat[SQLCOM_SHOW_FIELDS]);
     if (thd->copy_db_to(&db.str, &db.length))
@@ -1754,16 +1741,6 @@ bool sp_process_definer(THD *thd)
 /**
   Execute command saved in thd and lex->sql_command.
 
-    Before every operation that can request a write lock for a table
-    wait if a global read lock exists. However do not wait if this
-    thread has locked tables already. No new locks can be requested
-    until the other locks are released. The thread that requests the
-    global read lock waits for write locked tables to become unlocked.
-
-    Note that wait_if_global_read_lock() sets a protection against a new
-    global read lock when it succeeds. This needs to be released by
-    start_waiting_global_read_lock() after the operation.
-
   @param thd                       Thread handle
 
   @todo
@@ -1797,7 +1774,6 @@ mysql_execute_command(THD *thd)
   /* have table map for update for multi-update statement (BUG#37051) */
   bool have_table_map_for_update= FALSE;
 #endif
-  /* Saved variable value */
   DBUG_ENTER("mysql_execute_command");
 #ifdef WITH_PARTITION_STORAGE_ENGINE
   thd->work_part_info= 0;
@@ -1989,17 +1965,6 @@ mysql_execute_command(THD *thd)
     thd->mdl_context.release_transactional_locks();
   }
 
-  /*
-    Check if this command needs protection against the global read lock
-    to avoid deadlock. See CF_PROTECT_AGAINST_GRL.
-    start_waiting_global_read_lock() is called at the end of
-    mysql_execute_command().
-  */
-  if (((sql_command_flags[lex->sql_command] & CF_PROTECT_AGAINST_GRL) != 0) &&
-      !thd->locked_tables_mode)
-    if (thd->global_read_lock.wait_if_global_read_lock(thd, FALSE, TRUE))
-      goto error;
-
 #ifndef DBUG_OFF
   if (lex->sql_command != SQLCOM_SET_OPTION)
     DEBUG_SYNC(thd,"before_execute_sql_command");
@@ -2074,10 +2039,6 @@ mysql_execute_command(THD *thd)
     if (res)
       break;
 
-    if (!thd->locked_tables_mode && lex->protect_against_global_read_lock &&
-        thd->global_read_lock.wait_if_global_read_lock(thd, FALSE, TRUE))
-      break;
-
     res= execute_sqlcom_select(thd, all_tables);
     break;
   }
@@ -2336,20 +2297,6 @@ case SQLCOM_PREPARE:
       create_info.default_table_charset= create_info.table_charset;
       create_info.table_charset= 0;
     }
-    /*
-      The create-select command will open and read-lock the select table
-      and then create, open and write-lock the new table. If a global
-      read lock steps in, we get a deadlock. The write lock waits for
-      the global read lock, while the global read lock waits for the
-      select table to be closed. So we wait until the global readlock is
-      gone before starting both steps. Note that
-      wait_if_global_read_lock() sets a protection against a new global
-      read lock when it succeeds. This needs to be released by
-      start_waiting_global_read_lock(). We protect the normal CREATE
-      TABLE in the same way. That way we avoid that a new table is
-      created during a global read lock.
-      Protection against grl is covered by the CF_PROTECT_AGAINST_GRL flag.
-    */
 
 #ifdef WITH_PARTITION_STORAGE_ENGINE
     {
@@ -3143,9 +3090,6 @@ end_with_restore_list:
     if (check_table_access(thd, LOCK_TABLES_ACL | SELECT_ACL, all_tables,
                            FALSE, UINT_MAX, FALSE))
       goto error;
-    if (lex->protect_against_global_read_lock &&
-        thd->global_read_lock.wait_if_global_read_lock(thd, FALSE, TRUE))
-      goto error;
 
     thd->variables.option_bits|= OPTION_TABLE_LOCK;
     thd->in_lock_tables=1;
@@ -3801,13 +3745,22 @@ end_with_restore_list:
       Security_context *backup= NULL;
       LEX_USER *definer= thd->lex->definer;
       /*
-        We're going to issue an implicit GRANT statement.
-        It takes metadata locks and updates system tables.
-        Make sure that sp_create_routine() did not leave any
-        locks in the MDL context, so there is no risk to
-        deadlock.
+        We're going to issue an implicit GRANT statement so we close all
+        open tables. We have to keep metadata locks as this ensures that
+        this statement is atomic against concurent FLUSH TABLES WITH READ
+        LOCK. Deadlocks which can arise due to fact that this implicit
+        statement takes metadata locks should be detected by a deadlock
+        detector in MDL subsystem and reported as errors.
+
+        No need to commit/rollback statement transaction, it's not started.
+
+        TODO: Long-term we should either ensure that implicit GRANT statement
+              is written into binary log as a separate statement or make both
+              creation of routine and implicit GRANT parts of one fully atomic
+              statement.
       */
-      close_mysql_tables(thd);
+      DBUG_ASSERT(thd->transaction.stmt.is_empty());
+      close_thread_tables(thd);
       /*
         Check if the definer exists on slave, 
         then use definer privilege to insert routine privileges to mysql.procs_priv.
@@ -4067,13 +4020,22 @@ create_sp_error:
 
 #ifndef NO_EMBEDDED_ACCESS_CHECKS
       /*
-        We're going to issue an implicit REVOKE statement.
-        It takes metadata locks and updates system tables.
-        Make sure that sp_create_routine() did not leave any
-        locks in the MDL context, so there is no risk to
-        deadlock.
+        We're going to issue an implicit REVOKE statement so we close all
+        open tables. We have to keep metadata locks as this ensures that
+        this statement is atomic against concurent FLUSH TABLES WITH READ
+        LOCK. Deadlocks which can arise due to fact that this implicit
+        statement takes metadata locks should be detected by a deadlock
+        detector in MDL subsystem and reported as errors.
+
+        No need to commit/rollback statement transaction, it's not started.
+
+        TODO: Long-term we should either ensure that implicit REVOKE statement
+              is written into binary log as a separate statement or make both
+              dropping of routine and implicit REVOKE parts of one fully atomic
+              statement.
       */
-      close_mysql_tables(thd);
+      DBUG_ASSERT(thd->transaction.stmt.is_empty());
+      close_thread_tables(thd);
 
       if (sp_result != SP_KEY_NOT_FOUND &&
           sp_automatic_privileges && !opt_noacl &&
@@ -4362,14 +4324,6 @@ error:
   res= TRUE;
 
 finish:
-  if (thd->global_read_lock.has_protection())
-  {
-    /*
-      Release the protection against the global read lock and wake
-      everyone, who might want to set a global read lock.
-    */
-    thd->global_read_lock.start_waiting_global_read_lock(thd);
-  }
 
   DBUG_ASSERT(!thd->in_active_multi_stmt_transaction() ||
                thd->in_multi_stmt_transaction_mode());
@@ -4405,6 +4359,11 @@ finish:
   close_thread_tables(thd);
   thd_proc_info(thd, 0);
 
+#ifndef DBUG_OFF
+  if (lex->sql_command != SQLCOM_SET_OPTION && ! thd->in_sub_stmt)
+    DEBUG_SYNC(thd, "execute_command_after_close_tables");
+#endif
+
   if (stmt_causes_implicit_commit(thd, CF_IMPLICIT_COMMIT_END))
   {
     /* No transaction control allowed in sub-statements. */
@@ -4430,6 +4389,10 @@ finish:
     */
     thd->mdl_context.release_transactional_locks();
   }
+  else if (! thd->in_sub_stmt)
+  {
+    thd->mdl_context.release_statement_locks();
+  }
 
   DBUG_RETURN(res || thd->is_error());
 }
@@ -5899,7 +5862,8 @@ TABLE_LIST *st_select_lex::add_table_to_list(THD *thd,
   ptr->next_name_resolution_table= NULL;
   /* Link table in global list (all used tables) */
   lex->add_to_query_tables(ptr);
-  ptr->mdl_request.init(MDL_key::TABLE, ptr->db, ptr->table_name, mdl_type);
+  ptr->mdl_request.init(MDL_key::TABLE, ptr->db, ptr->table_name, mdl_type,
+                        MDL_TRANSACTION);
   DBUG_RETURN(ptr);
 }
 
diff --git a/sql/sql_prepare.cc b/sql/sql_prepare.cc
index fcbf2c48896..2b51305d099 100644
--- a/sql/sql_prepare.cc
+++ b/sql/sql_prepare.cc
@@ -3172,7 +3172,6 @@ bool Prepared_statement::prepare(const char *packet, uint packet_len)
   bool error;
   Statement stmt_backup;
   Query_arena *old_stmt_arena;
-  MDL_ticket *mdl_savepoint= NULL;
   DBUG_ENTER("Prepared_statement::prepare");
   /*
     If this is an SQLCOM_PREPARE, we also increase Com_prepare_sql.
@@ -3244,7 +3243,7 @@ bool Prepared_statement::prepare(const char *packet, uint packet_len)
     Marker used to release metadata locks acquired while the prepared
     statement is being checked.
   */
-  mdl_savepoint= thd->mdl_context.mdl_savepoint();
+  MDL_savepoint mdl_savepoint= thd->mdl_context.mdl_savepoint();
 
   /* 
    The only case where we should have items in the thd->free_list is
diff --git a/sql/sql_rename.cc b/sql/sql_rename.cc
index 8f990eae001..6a7b0b0b3ad 100644
--- a/sql/sql_rename.cc
+++ b/sql/sql_rename.cc
@@ -24,8 +24,7 @@
 #include "sql_table.h"                         // build_table_filename
 #include "sql_view.h"             // mysql_frm_type, mysql_rename_view
 #include "sql_trigger.h"
-#include "lock.h"       // wait_if_global_read_lock
-                        // start_waiting_global_read_lock
+#include "lock.h"       // MYSQL_OPEN_SKIP_TEMPORARY
 #include "sql_base.h"   // tdc_remove_table, lock_table_names,
 #include "sql_handler.h"                        // mysql_ha_rm_tables
 #include "datadict.h"
@@ -63,9 +62,6 @@ bool mysql_rename_tables(THD *thd, TABLE_LIST *table_list, bool silent)
 
   mysql_ha_rm_tables(thd, table_list);
 
-  if (thd->global_read_lock.wait_if_global_read_lock(thd, FALSE, TRUE))
-    DBUG_RETURN(1);
-
   if (logger.is_log_table_enabled(QUERY_LOG_GENERAL) ||
       logger.is_log_table_enabled(QUERY_LOG_SLOW))
   {
@@ -189,7 +185,6 @@ bool mysql_rename_tables(THD *thd, TABLE_LIST *table_list, bool silent)
     query_cache_invalidate3(thd, table_list, 0);
 
 err:
-  thd->global_read_lock.start_waiting_global_read_lock(thd);
   DBUG_RETURN(error || binlog_error);
 }
 
diff --git a/sql/sql_show.cc b/sql/sql_show.cc
index 19a73c85a9b..b8c66562b1a 100644
--- a/sql/sql_show.cc
+++ b/sql/sql_show.cc
@@ -671,7 +671,7 @@ mysqld_show_create(THD *thd, TABLE_LIST *table_list)
     Metadata locks taken during SHOW CREATE should be released when
     the statmement completes as it is an information statement.
   */
-  MDL_ticket *mdl_savepoint= thd->mdl_context.mdl_savepoint();
+  MDL_savepoint mdl_savepoint= thd->mdl_context.mdl_savepoint();
 
   /* We want to preserve the tree for views. */
   thd->lex->view_prepare_mode= TRUE;
@@ -3186,7 +3186,7 @@ try_acquire_high_prio_shared_mdl_lock(THD *thd, TABLE_LIST *table,
 {
   bool error;
   table->mdl_request.init(MDL_key::TABLE, table->db, table->table_name,
-                          MDL_SHARED_HIGH_PRIO);
+                          MDL_SHARED_HIGH_PRIO, MDL_TRANSACTION);
 
   if (can_deadlock)
   {
@@ -7745,7 +7745,7 @@ bool show_create_trigger(THD *thd, const sp_name *trg_name)
     Metadata locks taken during SHOW CREATE TRIGGER should be released when
     the statement completes as it is an information statement.
   */
-  MDL_ticket *mdl_savepoint= thd->mdl_context.mdl_savepoint();
+  MDL_savepoint mdl_savepoint= thd->mdl_context.mdl_savepoint();
 
   /*
     Open the table by name in order to load Table_triggers_list object.
diff --git a/sql/sql_table.cc b/sql/sql_table.cc
index 1c6ca4a48d9..ed0acc66e49 100644
--- a/sql/sql_table.cc
+++ b/sql/sql_table.cc
@@ -23,9 +23,7 @@
 #include "sql_parse.h"                        // test_if_data_home_dir
 #include "sql_cache.h"                          // query_cache_*
 #include "sql_base.h"   // open_table_uncached, lock_table_names
-#include "lock.h"       // wait_if_global_read_lock
-                        // start_waiting_global_read_lock,
-                        // mysql_unlock_tables
+#include "lock.h"       // mysql_unlock_tables
 #include "strfunc.h"    // find_type2, find_set
 #include "sql_view.h" // view_checksum 
 #include "sql_truncate.h"                       // regenerate_locked_table 
@@ -1855,21 +1853,10 @@ bool mysql_rm_table(THD *thd,TABLE_LIST *tables, my_bool if_exists,
   DBUG_ENTER("mysql_rm_table");
 
   /* mark for close and remove all cached entries */
-
-  if (!drop_temporary)
-  {
-    if (!thd->locked_tables_mode &&
-       thd->global_read_lock.wait_if_global_read_lock(thd, FALSE, TRUE))
-      DBUG_RETURN(TRUE);
-  }
-
   thd->push_internal_handler(&err_handler);
   error= mysql_rm_table_part2(thd, tables, if_exists, drop_temporary, 0, 0);
   thd->pop_internal_handler();
 
-  if (thd->global_read_lock.has_protection())
-    thd->global_read_lock.start_waiting_global_read_lock(thd);
-
   if (error)
     DBUG_RETURN(TRUE);
   my_ok(thd);
@@ -5592,7 +5579,6 @@ bool mysql_alter_table(THD *thd,char *new_db, char *new_name,
   TABLE *table, *new_table= 0;
   MDL_ticket *mdl_ticket;
   MDL_request target_mdl_request;
-  bool has_target_mdl_lock= FALSE;
   int error= 0;
   char tmp_name[80],old_name[32],new_name_buff[FN_REFLEN + 1];
   char new_alias_buff[FN_REFLEN], *table_name, *db, *new_alias, *alias;
@@ -5754,7 +5740,7 @@ bool mysql_alter_table(THD *thd,char *new_db, char *new_name,
       else
       {
         target_mdl_request.init(MDL_key::TABLE, new_db, new_name,
-                                MDL_EXCLUSIVE);
+                                MDL_EXCLUSIVE, MDL_TRANSACTION);
         /*
           Global intention exclusive lock must have been already acquired when
           table to be altered was open, so there is no need to do it here.
@@ -5772,7 +5758,6 @@ bool mysql_alter_table(THD *thd,char *new_db, char *new_name,
 	  DBUG_RETURN(TRUE);
         }
         DEBUG_SYNC(thd, "locked_table_name");
-        has_target_mdl_lock= TRUE;
         /*
           Table maybe does not exist, but we got an exclusive lock
           on the name, now we can safely try to find out for sure.
@@ -5959,10 +5944,7 @@ bool mysql_alter_table(THD *thd,char *new_db, char *new_name,
         along with the implicit commit.
       */
       if (new_name != table_name || new_db != db)
-      {
-        thd->mdl_context.release_lock(target_mdl_request.ticket);
         thd->mdl_context.release_all_locks_for_name(mdl_ticket);
-      }
       else
         mdl_ticket->downgrade_exclusive_lock(MDL_SHARED_NO_READ_WRITE);
     }
@@ -6667,10 +6649,7 @@ bool mysql_alter_table(THD *thd,char *new_db, char *new_name,
       thd->locked_tables_mode == LTM_PRELOCKED_UNDER_LOCK_TABLES)
   {
     if ((new_name != table_name || new_db != db))
-    {
-      thd->mdl_context.release_lock(target_mdl_request.ticket);
       thd->mdl_context.release_all_locks_for_name(mdl_ticket);
-    }
     else
       mdl_ticket->downgrade_exclusive_lock(MDL_SHARED_NO_READ_WRITE);
   }
@@ -6731,8 +6710,6 @@ err:
                                  alter_info->datetime_field->field_name);
     thd->abort_on_warning= save_abort_on_warning;
   }
-  if (has_target_mdl_lock)
-    thd->mdl_context.release_lock(target_mdl_request.ticket);
 
   DBUG_RETURN(TRUE);
 
@@ -6744,9 +6721,6 @@ err_with_mdl:
     tables and release the exclusive metadata lock.
   */
   thd->locked_tables_list.unlink_all_closed_tables(thd, NULL, 0);
-  if (has_target_mdl_lock)
-    thd->mdl_context.release_lock(target_mdl_request.ticket);
-
   thd->mdl_context.release_all_locks_for_name(mdl_ticket);
   DBUG_RETURN(TRUE);
 }
diff --git a/sql/sql_trigger.cc b/sql/sql_trigger.cc
index a9b52eee9fc..c2e3cd9944a 100644
--- a/sql/sql_trigger.cc
+++ b/sql/sql_trigger.cc
@@ -24,8 +24,6 @@
 #include "parse_file.h"
 #include "sp.h"
 #include "sql_base.h"                          // find_temporary_table
-#include "lock.h"                    // wait_if_global_read_lock,
-                                     // start_waiting_global_read_lock
 #include "sql_show.h"                // append_definer, append_identifier
 #include "sql_table.h"                        // build_table_filename,
                                               // check_n_cut_mysql50_prefix
@@ -391,15 +389,6 @@ bool mysql_create_or_drop_trigger(THD *thd, TABLE_LIST *tables, bool create)
     DBUG_RETURN(TRUE);
   }
 
-  /*
-    We don't want perform our operations while global read lock is held
-    so we have to wait until its end and then prevent it from occurring
-    again until we are done, unless we are under lock tables.
-  */
-  if (!thd->locked_tables_mode &&
-      thd->global_read_lock.wait_if_global_read_lock(thd, FALSE, TRUE))
-    DBUG_RETURN(TRUE);
-
   if (!create)
   {
     bool if_exists= thd->lex->drop_if_exists;
@@ -547,9 +536,6 @@ end:
   if (!create)
     thd->lex->restore_backup_query_tables_list(&backup);
 
-  if (thd->global_read_lock.has_protection())
-    thd->global_read_lock.start_waiting_global_read_lock(thd);
-
   if (!result)
     my_ok(thd);
 
diff --git a/sql/sql_update.cc b/sql/sql_update.cc
index 96b1ac67b49..8a9feb1b3f8 100644
--- a/sql/sql_update.cc
+++ b/sql/sql_update.cc
@@ -1026,9 +1026,17 @@ int mysql_multi_update_prepare(THD *thd)
   /* following need for prepared statements, to run next time multi-update */
   thd->lex->sql_command= SQLCOM_UPDATE_MULTI;
 
-  /* open tables and create derived ones, but do not lock and fill them */
+  /*
+    Open tables and create derived ones, but do not lock and fill them yet.
+
+    During prepare phase acquire only S metadata locks instead of SW locks to
+    keep prepare of multi-UPDATE compatible with concurrent LOCK TABLES WRITE
+    and global read lock.
+  */
   if ((original_multiupdate &&
-       open_tables(thd, &table_list, &table_count, 0)) ||
+       open_tables(thd, &table_list, &table_count,
+                   (thd->stmt_arena->is_stmt_prepare() ?
+                    MYSQL_OPEN_FORCE_SHARED_MDL : 0))) ||
       mysql_handle_derived(lex, &mysql_derived_prepare))
     DBUG_RETURN(TRUE);
   /*
diff --git a/sql/sql_view.cc b/sql/sql_view.cc
index 5fdf7b8d850..54b5eb43ab1 100644
--- a/sql/sql_view.cc
+++ b/sql/sql_view.cc
@@ -22,7 +22,7 @@
 #include "sql_base.h"    // find_table_in_global_list, lock_table_names
 #include "sql_parse.h"                          // sql_parse
 #include "sql_cache.h"                          // query_cache_*
-#include "lock.h"        // wait_if_global_read_lock
+#include "lock.h"        // MYSQL_OPEN_SKIP_TEMPORARY 
 #include "sql_show.h"    // append_identifier
 #include "sql_table.h"                         // build_table_filename
 #include "sql_db.h"            // mysql_opt_change_db, mysql_change_db
@@ -649,13 +649,6 @@ bool mysql_create_view(THD *thd, TABLE_LIST *views,
   }
 #endif
 
-
-  if (thd->global_read_lock.wait_if_global_read_lock(thd, FALSE, TRUE))
-  {
-    res= TRUE;
-    goto err;
-  }
-
   res= mysql_register_view(thd, view, mode);
 
   if (mysql_bin_log.is_open())
@@ -704,7 +697,6 @@ bool mysql_create_view(THD *thd, TABLE_LIST *views,
 
   if (mode != VIEW_CREATE_NEW)
     query_cache_invalidate3(thd, view, 0);
-  thd->global_read_lock.start_waiting_global_read_lock(thd);
   if (res)
     goto err;
 
diff --git a/sql/sql_yacc.yy b/sql/sql_yacc.yy
index 66d74a398fb..9aa938437b1 100644
--- a/sql/sql_yacc.yy
+++ b/sql/sql_yacc.yy
@@ -7385,7 +7385,6 @@ select_lock_type:
             LEX *lex=Lex;
             lex->current_select->set_lock_for_tables(TL_WRITE);
             lex->safe_to_cache_query=0;
-            lex->protect_against_global_read_lock= TRUE;
           }
         | LOCK_SYM IN_SYM SHARE_SYM MODE_SYM
           {
@@ -13182,9 +13181,6 @@ table_lock:
                                             MDL_SHARED_NO_READ_WRITE :
                                             MDL_SHARED_READ)))
               MYSQL_YYABORT;
-            /* If table is to be write locked, protect from a impending GRL. */
-            if (lock_for_write)
-              Lex->protect_against_global_read_lock= TRUE;
           }
         ;
 
diff --git a/sql/table.cc b/sql/table.cc
index f55095d6e82..8cd2e9e9bab 100644
--- a/sql/table.cc
+++ b/sql/table.cc
@@ -5219,7 +5219,8 @@ void init_mdl_requests(TABLE_LIST *table_list)
     table_list->mdl_request.init(MDL_key::TABLE,
                                  table_list->db, table_list->table_name,
                                  table_list->lock_type >= TL_WRITE_ALLOW_WRITE ?
-                                 MDL_SHARED_WRITE : MDL_SHARED_READ);
+                                 MDL_SHARED_WRITE : MDL_SHARED_READ,
+                                 MDL_TRANSACTION);
 }
 
 
diff --git a/sql/table.h b/sql/table.h
index c8e1ad8e658..6aba4f21db2 100644
--- a/sql/table.h
+++ b/sql/table.h
@@ -1384,7 +1384,8 @@ struct TABLE_LIST
     lock_type= lock_type_arg;
     mdl_request.init(MDL_key::TABLE, db, table_name,
                      (lock_type >= TL_WRITE_ALLOW_WRITE) ?
-                     MDL_SHARED_WRITE : MDL_SHARED_READ);
+                     MDL_SHARED_WRITE : MDL_SHARED_READ,
+                     MDL_TRANSACTION);
   }
 
   /*
diff --git a/sql/transaction.cc b/sql/transaction.cc
index d3e3ba142b9..b331fea89fe 100644
--- a/sql/transaction.cc
+++ b/sql/transaction.cc
@@ -21,6 +21,7 @@
 #include "sql_priv.h"
 #include "transaction.h"
 #include "rpl_handler.h"
+#include "debug_sync.h"         // DEBUG_SYNC
 
 /* Conditions under which the transaction state must not change. */
 static bool trans_check(THD *thd)
@@ -391,15 +392,15 @@ bool trans_savepoint(THD *thd, LEX_STRING name)
   thd->transaction.savepoints= newsv;
 
   /*
-    Remember the last acquired lock before the savepoint was set.
-    This is used as a marker to only release locks acquired after
+    Remember locks acquired before the savepoint was set.
+    They are used as a marker to only release locks acquired after
     the setting of this savepoint.
     Note: this works just fine if we're under LOCK TABLES,
     since mdl_savepoint() is guaranteed to be beyond
     the last locked table. This allows to release some
     locks acquired during LOCK TABLES.
   */
-  newsv->mdl_savepoint = thd->mdl_context.mdl_savepoint();
+  newsv->mdl_savepoint= thd->mdl_context.mdl_savepoint();
 
   DBUG_RETURN(FALSE);
 }
@@ -645,17 +646,31 @@ bool trans_xa_commit(THD *thd)
   }
   else if (xa_state == XA_PREPARED && thd->lex->xa_opt == XA_NONE)
   {
-    if (thd->global_read_lock.wait_if_global_read_lock(thd, FALSE, FALSE))
+    MDL_request mdl_request;
+
+    /*
+      Acquire metadata lock which will ensure that COMMIT is blocked
+      by active FLUSH TABLES WITH READ LOCK (and vice versa COMMIT in
+      progress blocks FTWRL).
+
+      We allow FLUSHer to COMMIT; we assume FLUSHer knows what it does.
+    */
+    mdl_request.init(MDL_key::COMMIT, "", "", MDL_INTENTION_EXCLUSIVE,
+                     MDL_TRANSACTION);
+
+    if (thd->mdl_context.acquire_lock(&mdl_request,
+                                      thd->variables.lock_wait_timeout))
     {
       ha_rollback_trans(thd, TRUE);
       my_error(ER_XAER_RMERR, MYF(0));
     }
     else
     {
+      DEBUG_SYNC(thd, "trans_xa_commit_after_acquire_commit_lock");
+
       res= test(ha_commit_one_phase(thd, 1));
       if (res)
         my_error(ER_XAER_RMERR, MYF(0));
-      thd->global_read_lock.start_waiting_global_read_lock(thd);
     }
   }
   else