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

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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.
This commit is contained in:
Jon Olav Hauglid
2010-02-24 18:04:00 +01:00
parent b6e0f92f05
commit dd42aab840
24 changed files with 128 additions and 114 deletions
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21
sql/sql_table.cc
View File

@ -4227,8 +4227,7 @@ bool mysql_create_table(THD *thd, TABLE_LIST *create_table,
/*
Open or obtain an exclusive metadata lock on table being created.
*/
if (open_and_lock_tables_derived(thd, thd->lex->query_tables, FALSE,
0))
if (open_and_lock_tables(thd, thd->lex->query_tables, FALSE, 0))
{
result= TRUE;
goto unlock;
@ -4427,7 +4426,7 @@ static int prepare_for_repair(THD *thd, TABLE_LIST *table_list,
char from[FN_REFLEN],tmp[FN_REFLEN+32];
const char **ext;
MY_STAT stat_info;
Open_table_context ot_ctx_unused(thd);
Open_table_context ot_ctx_unused(thd, LONG_TIMEOUT);
DBUG_ENTER("prepare_for_repair");
uint reopen_for_repair_flags= (MYSQL_LOCK_IGNORE_FLUSH |
MYSQL_OPEN_HAS_MDL_LOCK);
@ -4679,8 +4678,8 @@ static bool mysql_admin_table(THD* thd, TABLE_LIST* tables,
if (view_operator_func == NULL)
table->required_type=FRMTYPE_TABLE;
open_error= open_and_lock_tables_derived(thd, table, TRUE,
MYSQL_OPEN_TAKE_UPGRADABLE_MDL);
open_error= open_and_lock_tables(thd, table, TRUE,
MYSQL_OPEN_TAKE_UPGRADABLE_MDL);
thd->no_warnings_for_error= 0;
table->next_global= save_next_global;
table->next_local= save_next_local;
@ -5349,7 +5348,7 @@ bool mysql_create_like_table(THD* thd, TABLE_LIST* table, TABLE_LIST* src_table,
char buf[2048];
String query(buf, sizeof(buf), system_charset_info);
query.length(0); // Have to zero it since constructor doesn't
Open_table_context ot_ctx_unused(thd);
Open_table_context ot_ctx_unused(thd, LONG_TIMEOUT);
/*
The condition avoids a crash as described in BUG#48506. Other
@ -6558,9 +6557,9 @@ view_err:
Alter_table_prelocking_strategy alter_prelocking_strategy(alter_info);
error= open_and_lock_tables_derived(thd, table_list, FALSE,
MYSQL_OPEN_TAKE_UPGRADABLE_MDL,
&alter_prelocking_strategy);
error= open_and_lock_tables(thd, table_list, FALSE,
MYSQL_OPEN_TAKE_UPGRADABLE_MDL,
&alter_prelocking_strategy);
if (error)
{
@ -7148,7 +7147,7 @@ view_err:
{
if (table->s->tmp_table)
{
Open_table_context ot_ctx_unused(thd);
Open_table_context ot_ctx_unused(thd, LONG_TIMEOUT);
TABLE_LIST tbl;
bzero((void*) &tbl, sizeof(tbl));
tbl.db= new_db;
@ -7433,7 +7432,7 @@ view_err:
To do this we need to obtain a handler object for it.
NO need to tamper with MERGE tables. The real open is done later.
*/
Open_table_context ot_ctx_unused(thd);
Open_table_context ot_ctx_unused(thd, LONG_TIMEOUT);
TABLE *t_table;
if (new_name != table_name || new_db != db)
{