A 5.5 version of the fix for Bug #54360 "Deadlock DROP/ALTER/CREATE

DATABASE with open HANDLER"

Remove LOCK_create_db, database name locks, and use metadata locks instead.
This exposes CREATE/DROP/ALTER DATABASE statements to the graph-based
deadlock detector in MDL, and paves the way for a safe, deadlock-free
implementation of RENAME DATABASE.

Database DDL statements will now take exclusive metadata locks on
the database name, while table/view/routine DDL statements take
intention exclusive locks on the database name. This prevents race
conditions between database DDL and table/view/routine DDL.
(e.g. DROP DATABASE with concurrent CREATE/ALTER/DROP TABLE)

By adding database name locks, this patch implements
WL#4450 "DDL locking: CREATE/DROP DATABASE must use database locks" and
WL#4985 "DDL locking: namespace/hierarchical locks".

The patch also changes code to use init_one_table() where appropriate.
The new lock_table_names() function requires TABLE_LIST::db_length to
be set correctly, and this is taken care of by init_one_table().

This patch also adds a simple template to help work with 
the mysys HASH data structure.

Most of the patch was written by Konstantin Osipov.

1 files changed, 7 insertions, 14 deletions

diff --git a/sql/mysqld.cc b/sql/mysqld.cc
index 28cad51aa41..0ba796a5eb8 100644
--- a/sql/mysqld.cc
+++ b/sql/mysqld.cc
@@ -27,8 +27,8 @@
                           // reset_status_vars
 #include "strfunc.h"      // find_set_from_flags
 #include "parse_file.h"   // File_parser_dummy_hook
-#include "sql_db.h"       // my_database_names_free,
-                          // my_database_names_init
+#include "sql_db.h"       // my_dboptions_cache_free
+                          // my_dboptions_cache_init
 #include "sql_table.h"    // release_ddl_log, execute_ddl_log_recovery
 #include "sql_connect.h"  // free_max_user_conn, init_max_user_conn,
                           // handle_one_connection
@@ -653,7 +653,7 @@ SHOW_COMP_OPTION have_profiling;
 pthread_key(MEM_ROOT**,THR_MALLOC);
 pthread_key(THD*, THR_THD);
 mysql_mutex_t LOCK_thread_count;
-mysql_mutex_t LOCK_mysql_create_db, LOCK_open,
+mysql_mutex_t LOCK_open,
   LOCK_mapped_file, LOCK_status, LOCK_global_read_lock,
   LOCK_error_log, LOCK_uuid_generator,
   LOCK_delayed_insert, LOCK_delayed_status, LOCK_delayed_create,
@@ -1488,7 +1488,7 @@ void clean_up(bool print_message)
     bitmap_free(&slave_error_mask);
 #endif
   my_tz_free();
-  my_database_names_free();
+  my_dboptions_cache_free();
 #ifndef NO_EMBEDDED_ACCESS_CHECKS
   servers_free(1);
   acl_free(1);
@@ -1597,8 +1597,6 @@ static void wait_for_signal_thread_to_end()
 
 static void clean_up_mutexes()
 {
-  mysql_mutex_destroy(&LOCK_mysql_create_db);
-  mysql_mutex_destroy(&LOCK_lock_db);
   mysql_rwlock_destroy(&LOCK_grant);
   mysql_mutex_destroy(&LOCK_open);
   mysql_mutex_destroy(&LOCK_thread_count);
@@ -3730,7 +3728,7 @@ static int init_common_variables()
   use_temp_pool= 0;
 #endif
 
-  if (my_database_names_init())
+  if (my_dboptions_cache_init())
     return 1;
 
   /*
@@ -3787,9 +3785,6 @@ You should consider changing lower_case_table_names to 1 or 2",
 
 static int init_thread_environment()
 {
-  mysql_mutex_init(key_LOCK_mysql_create_db,
-                   &LOCK_mysql_create_db, MY_MUTEX_INIT_SLOW);
-  mysql_mutex_init(key_LOCK_lock_db, &LOCK_lock_db, MY_MUTEX_INIT_SLOW);
   mysql_mutex_init(key_LOCK_open, &LOCK_open, MY_MUTEX_INIT_FAST);
   mysql_mutex_init(key_LOCK_thread_count, &LOCK_thread_count, MY_MUTEX_INIT_FAST);
   mysql_mutex_init(key_LOCK_mapped_file, &LOCK_mapped_file, MY_MUTEX_INIT_SLOW);
@@ -8007,8 +8002,8 @@ PSI_mutex_key key_BINLOG_LOCK_index, key_BINLOG_LOCK_prep_xids,
   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_lock_db, key_LOCK_manager, key_LOCK_mapped_file,
-  key_LOCK_mysql_create_db, key_LOCK_open, key_LOCK_prepared_stmt_count,
+  key_LOCK_manager, key_LOCK_mapped_file,
+  key_LOCK_open, key_LOCK_prepared_stmt_count,
   key_LOCK_rpl_status, key_LOCK_server_started, key_LOCK_status,
   key_LOCK_system_variables_hash, key_LOCK_table_share, key_LOCK_thd_data,
   key_LOCK_user_conn, key_LOCK_uuid_generator, key_LOG_LOCK_log,
@@ -8046,10 +8041,8 @@ static PSI_mutex_info all_server_mutexes[]=
   { &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_lock_db, "LOCK_lock_db", PSI_FLAG_GLOBAL},
   { &key_LOCK_manager, "LOCK_manager", PSI_FLAG_GLOBAL},
   { &key_LOCK_mapped_file, "LOCK_mapped_file", PSI_FLAG_GLOBAL},
-  { &key_LOCK_mysql_create_db, "LOCK_mysql_create_db", PSI_FLAG_GLOBAL},
   { &key_LOCK_open, "LOCK_open", PSI_FLAG_GLOBAL},
   { &key_LOCK_prepared_stmt_count, "LOCK_prepared_stmt_count", PSI_FLAG_GLOBAL},
   { &key_LOCK_rpl_status, "LOCK_rpl_status", PSI_FLAG_GLOBAL},