Backport of:

------------------------------------------------------------
revno: 2630.4.32
committer: Dmitry Lenev <dlenev@mysql.com>
branch nick: mysql-6.0-3726-w2
timestamp: Thu 2008-06-19 16:39:58 +0400
message:
  WL#3726 "DDL locking for all metadata objects".

  After-review fixes in progress.

  Ensure that metadata locking subsystem properly handles
  out-of-memory conditions. Clarified MDL interface by
  separating release of locks and removal of lock requests
  from the context.

sql/lock.cc:
  mdl_release_lock(), mdl_acquire_exclusive_locks() and 
  mdl_try_acquire_exclusive_lock() are no longer responsible
  for removal of metadata lock requests from the context.
  One should explicitly call mdl_remove_all_locks() and
  mdl_remove_lock() to do this.
sql/mdl.cc:
  Ensured that metadata locking subsystem properly handles
  out-of-memory conditions.
  Introduced new MDL_INITIALIZED state for metadata lock
  request which is used in all cases when lock is not acquired 
  and we have not associated request with object respesenting 
  lock.
  
  MDL_PENDING is now only used for requests for exclusive locks
  which are added to the MDL_LOCK::waiting_exclusive queue.
  mdl_release_lock(), mdl_acquire_exclusive_locks() and 
  mdl_try_acquire_exclusive_lock() are no longer responsible
  for removal of metadata lock requests from the context.
  One should explicitly call mdl_remove_all_locks() and
  newly introduced mdl_remove_lock() to do this.
  Also renamed mdl_release_all_locks_for_name() to 
  emphasize that it also actually removes lock requests
  from the context.
  
  Finally mdl_try_acquire_exclusive_lock() is now returs
  information about encountered lock conflict in separate
  out parameter since its return value is used for distinguishing
  between error (e.g. due to OOM) and success.
sql/mdl.h:
  Introduced new MDL_INITIALIZED state for metadata lock
  request which is used in all cases when lock is not acquired 
  and we have not associated request with object respesenting 
  lock.
  
  MDL_PENDING is now only used for requests for exclusive locks
  which are added to the MDL_LOCK::waiting_exclusive queue.
  mdl_release_lock(), mdl_acquire_exclusive_locks() and 
  mdl_try_acquire_exclusive_lock() are no longer responsible
  for removal of metadata lock requests from the context.
  One should explicitly call mdl_remove_all_locks() and
  newly introduced mdl_remove_lock() to do this.
  Also renamed mdl_release_all_locks_for_name() to 
  emphasize that it also actually removes lock requests
  from the context.
  
  Finally mdl_try_acquire_exclusive_lock() is now returs
  information about encountered lock conflict in separate
  out parameter since its return value is used for distinguishing
  between error (e.g. due to OOM) and success.
sql/sql_base.cc:
  mdl_release_lock(), mdl_acquire_exclusive_locks() and mdl_try_acquire_exclusive_lock() are no longer responsible
  for removal of metadata lock requests from the context.
  One should explicitly call mdl_remove_all_locks() and
  mdl_remove_lock() to do this.
  Also adjusted open_table() to ensure that it 
  releases/removes metadata locks in case of error 
  after adding/acquiring them (unless keeping these
  lock requests is required for recovering action).
sql/sql_delete.cc:
  mdl_release_lock(), mdl_acquire_exclusive_locks() and mdl_try_acquire_exclusive_lock() are no longer responsible
  for removal of metadata lock requests from the context.
  One should explicitly call mdl_remove_all_locks() and
  mdl_remove_lock() to do this.
sql/sql_handler.cc:
  mdl_release_lock(), mdl_acquire_exclusive_locks() and mdl_try_acquire_exclusive_lock() are no longer responsible
  for removal of metadata lock requests from the context.
  One should explicitly call mdl_remove_all_locks() and
  mdl_remove_lock() to do this.
sql/sql_show.cc:
  mdl_release_lock(), mdl_acquire_exclusive_locks() and mdl_try_acquire_exclusive_lock() are no longer responsible
  for removal of metadata lock requests from the context.
  One should explicitly call mdl_remove_all_locks() and
  mdl_remove_lock() to do this.
sql/sql_table.cc:
  Renamed mdl_release_all_locks_for_name() to emphasize
  that it also actually removes lock requests from the context.
  mdl_release_lock(), mdl_acquire_exclusive_locks() and mdl_try_acquire_exclusive_lock() are no longer responsible
  for removal of metadata lock requests from the context.
  One should explicitly call mdl_remove_all_locks() and
  mdl_remove_lock() to do this.
  Finally mdl_try_acquire_exclusive_lock() is now returs
  information about encountered lock conflict in separate
  out parameter since its return value is used for distinguishing
  between error (e.g. due to OOM) and success.

1 files changed, 8 insertions, 5 deletions

diff --git a/sql/mdl.h b/sql/mdl.h
index b192980ebaa..92bd83038e5 100644
--- a/sql/mdl.h
+++ b/sql/mdl.h
@@ -44,7 +44,8 @@ enum enum_mdl_type {MDL_SHARED=0, MDL_SHARED_HIGH_PRIO,
 
 /** States which metadata lock request can have. */
 
-enum enum_mdl_state {MDL_PENDING=0, MDL_ACQUIRED, MDL_PENDING_UPGRADE};
+enum enum_mdl_state {MDL_INITIALIZED=0, MDL_PENDING,
+                     MDL_ACQUIRED, MDL_PENDING_UPGRADE};
 
 
 /**
@@ -152,6 +153,7 @@ void mdl_init_lock(MDL_LOCK_DATA *lock_data, char *key, int type,
 MDL_LOCK_DATA *mdl_alloc_lock(int type, const char *db, const char *name,
                               MEM_ROOT *root);
 void mdl_add_lock(MDL_CONTEXT *context, MDL_LOCK_DATA *lock_data);
+void mdl_remove_lock(MDL_CONTEXT *context, MDL_LOCK_DATA *lock_data);
 void mdl_remove_all_locks(MDL_CONTEXT *context);
 
 /**
@@ -160,7 +162,7 @@ void mdl_remove_all_locks(MDL_CONTEXT *context);
 
 inline void mdl_set_lock_type(MDL_LOCK_DATA *lock_data, enum_mdl_type lock_type)
 {
-  DBUG_ASSERT(lock_data->state == MDL_PENDING);
+  DBUG_ASSERT(lock_data->state == MDL_INITIALIZED);
   lock_data->type= lock_type;
 }
 
@@ -170,14 +172,15 @@ bool mdl_acquire_exclusive_locks(MDL_CONTEXT *context);
 bool mdl_upgrade_shared_lock_to_exclusive(MDL_CONTEXT *context,
                                           MDL_LOCK_DATA *lock_data);
 bool mdl_try_acquire_exclusive_lock(MDL_CONTEXT *context,
-                                    MDL_LOCK_DATA *lock_data);
+                                    MDL_LOCK_DATA *lock_data,
+                                    bool *conflict);
 bool mdl_acquire_global_shared_lock(MDL_CONTEXT *context);
 
 bool mdl_wait_for_locks(MDL_CONTEXT *context);
 
 void mdl_release_locks(MDL_CONTEXT *context);
-void mdl_release_all_locks_for_name(MDL_CONTEXT *context,
-                                    MDL_LOCK_DATA *lock_data);
+void mdl_release_and_remove_all_locks_for_name(MDL_CONTEXT *context,
+                                               MDL_LOCK_DATA *lock_data);
 void mdl_release_lock(MDL_CONTEXT *context, MDL_LOCK_DATA *lock_data);
 void mdl_downgrade_exclusive_lock(MDL_CONTEXT *context,
                                   MDL_LOCK_DATA *lock_data);