Followup to Bug#45225 Locking: hang if drop table with no timeout

This patch prevents system threads and system table accesses from
using user-specified values for "lock_wait_timeout". Instead all
such accesses are done using the default value (1 year).

This prevents background tasks (such as replication, events, 
accessing stored function definitions, logging, reading time-zone
information, etc.) from failing in cases where the global value
of "lock_wait_timeout" is set very low.

The patch also simplifies the open tables API. Rather than adding
another convenience function for opening and locking system tables,
this patch removes most of the existing convenience functions for
open_and_lock_tables_derived(). Before, open_and_lock_tables() was
a convenience function that enforced derived tables handling, while
open_and_lock_tables_derived() was the main function where derived
tables handling was optional. Now, this convencience function is
gone and the main function is renamed to open_and_lock_tables(). 

No test case added as it would have required the use of --sleep to
check that system threads and system tables have a different timeout
value from the user-specified "lock_wait_timeout" system variable.

1 files changed, 9 insertions, 9 deletions

diff --git a/sql/sql_acl.cc b/sql/sql_acl.cc
index fb257a6e5ec..86f62d9bf72 100644
--- a/sql/sql_acl.cc
+++ b/sql/sql_acl.cc
@@ -675,7 +675,7 @@ my_bool acl_reload(THD *thd)
   tables[0].open_type= tables[1].open_type= tables[2].open_type= OT_BASE_ONLY;
   init_mdl_requests(tables);
 
-  if (simple_open_n_lock_tables(thd, tables))
+  if (open_and_lock_tables(thd, tables, FALSE, MYSQL_LOCK_IGNORE_TIMEOUT))
   {
     /*
       Execution might have been interrupted; only print the error message
@@ -1602,7 +1602,7 @@ bool change_password(THD *thd, const char *host, const char *user,
   }
 #endif
 
-  if (!(table= open_ltable(thd, &tables, TL_WRITE, 0)))
+  if (!(table= open_ltable(thd, &tables, TL_WRITE, MYSQL_LOCK_IGNORE_TIMEOUT)))
     DBUG_RETURN(1);
 
   mysql_mutex_lock(&acl_cache->lock);
@@ -3040,7 +3040,7 @@ int mysql_table_grant(THD *thd, TABLE_LIST *table_list,
       class LEX_COLUMN *column;
       List_iterator <LEX_COLUMN> column_iter(columns);
 
-      if (open_and_lock_tables(thd, table_list))
+      if (open_and_lock_tables(thd, table_list, TRUE, 0))
         DBUG_RETURN(TRUE);
 
       while ((column = column_iter++))
@@ -3146,7 +3146,7 @@ int mysql_table_grant(THD *thd, TABLE_LIST *table_list,
   */
   Query_tables_list backup;
   thd->lex->reset_n_backup_query_tables_list(&backup);
-  if (simple_open_n_lock_tables(thd,tables))
+  if (open_and_lock_tables(thd, tables, FALSE, MYSQL_LOCK_IGNORE_TIMEOUT))
   {						// Should never happen
     close_thread_tables(thd);			/* purecov: deadcode */
     /* Restore the state of binlog format */
@@ -3374,7 +3374,7 @@ bool mysql_routine_grant(THD *thd, TABLE_LIST *table_list, bool is_proc,
   }
 #endif
 
-  if (simple_open_n_lock_tables(thd,tables))
+  if (open_and_lock_tables(thd, tables, FALSE, MYSQL_LOCK_IGNORE_TIMEOUT))
   {						// Should never happen
     close_thread_tables(thd);
     /* Restore the state of binlog format */
@@ -3531,7 +3531,7 @@ bool mysql_grant(THD *thd, const char *db, List <LEX_USER> &list,
   }
 #endif
 
-  if (simple_open_n_lock_tables(thd,tables))
+  if (open_and_lock_tables(thd, tables, FALSE, MYSQL_LOCK_IGNORE_TIMEOUT))
   {						// This should never happen
     close_thread_tables(thd);			/* purecov: deadcode */
     /* Restore the state of binlog format */
@@ -3853,7 +3853,7 @@ static my_bool grant_reload_procs_priv(THD *thd)
                        TL_READ);
   table.open_type= OT_BASE_ONLY;
 
-  if (simple_open_n_lock_tables(thd, &table))
+  if (open_and_lock_tables(thd, &table, FALSE, MYSQL_LOCK_IGNORE_TIMEOUT))
   {
     close_thread_tables(thd);
     DBUG_RETURN(TRUE);
@@ -3924,7 +3924,7 @@ my_bool grant_reload(THD *thd)
     To avoid deadlocks we should obtain table locks before
     obtaining LOCK_grant rwlock.
   */
-  if (simple_open_n_lock_tables(thd, tables))
+  if (open_and_lock_tables(thd, tables, FALSE, MYSQL_LOCK_IGNORE_TIMEOUT))
     goto end;
 
   mysql_rwlock_wrlock(&LOCK_grant);
@@ -5227,7 +5227,7 @@ int open_grant_tables(THD *thd, TABLE_LIST *tables)
   }
 #endif
 
-  if (simple_open_n_lock_tables(thd, tables))
+  if (open_and_lock_tables(thd, tables, FALSE, MYSQL_LOCK_IGNORE_TIMEOUT))
   {						// This should never happen
     close_thread_tables(thd);
     DBUG_RETURN(-1);