database/mariadb
1
0
Fork 0
mirror of https://github.com/MariaDB/server.git synced 2025-07-27 18:02:13 +03:00
Code Activity

Bug#16986 - Deadlock condition with MyISAM tables

Browse Source 
Addendum fixes after changing the condition variable
for the global read lock.

The stress test suite revealed some deadlocks. Some were
related to the new condition variable (COND_global_read_lock)
and some were general problems with the global read lock.

It is now necessary to signal COND_global_read_lock whenever 
COND_refresh is signalled.

We need to wait for the release of a global read lock if one 
is set before every operation that requires a write lock.
But we must not wait if we have locked tables by LOCK TABLES.
After setting a global read lock a thread waits until all
write locks are released.
This commit is contained in:
ingo@mysql.com
2006-06-26 19:14:35 +02:00
parent fa98891ee7
commit d27a15a81c
10 changed files with 208 additions and 66 deletions
Download Patch File Download Diff File Expand all files Collapse all files

102
sql/sql_parse.cc
View File

@ -2337,17 +2337,37 @@ static void reset_one_shot_variables(THD *thd)
}
/****************************************************************************
** mysql_execute_command
** Execute command saved in thd and current_lex->sql_command
****************************************************************************/
/*
Execute command saved in thd and current_lex->sql_command
SYNOPSIS
mysql_execute_command()
thd Thread handle
IMPLEMENTATION
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.
RETURN
FALSE OK
TRUE Error
*/
bool
mysql_execute_command(THD *thd)
{
bool res= FALSE;
int result= 0;
LEX *lex= thd->lex;
bool res= FALSE;
bool need_start_waiting= FALSE; // have protection against global read lock
int result= 0;
LEX *lex= thd->lex;
/* first SELECT_LEX (have special meaning for many of non-SELECTcommands) */
SELECT_LEX *select_lex= &lex->select_lex;
/* first table of first SELECT_LEX */
@ -2832,7 +2852,8 @@ mysql_execute_command(THD *thd)
TABLE in the same way. That way we avoid that a new table is
created during a gobal read lock.
*/
if (wait_if_global_read_lock(thd, 0, 1))
if (!thd->locked_tables &&
!(need_start_waiting= !wait_if_global_read_lock(thd, 0, 1)))
{
res= 1;
goto end_with_restore_list;
@ -2857,7 +2878,7 @@ mysql_execute_command(THD *thd)
{
update_non_unique_table_error(create_table, "CREATE", duplicate);
res= 1;
goto end_with_restart_wait;
goto end_with_restore_list;
}
}
/* If we create merge table, we have to test tables in merge, too */
@ -2873,7 +2894,7 @@ mysql_execute_command(THD *thd)
{
update_non_unique_table_error(tab, "CREATE", duplicate);
res= 1;
goto end_with_restart_wait;
goto end_with_restore_list;
}
}
}
@ -2915,13 +2936,6 @@ mysql_execute_command(THD *thd)
send_ok(thd);
}
end_with_restart_wait:
/*
Release the protection against the global read lock and wake
everyone, who might want to set a global read lock.
*/
start_waiting_global_read_lock(thd);
/* put tables back for PS rexecuting */
end_with_restore_list:
lex->link_first_table_back(create_table, link_to_local);
@ -3039,6 +3053,13 @@ end_with_restore_list:
goto error;
else
{
if (!thd->locked_tables &&
!(need_start_waiting= !wait_if_global_read_lock(thd, 0, 1)))
{
res= 1;
break;
}
thd->enable_slow_log= opt_log_slow_admin_statements;
res= mysql_alter_table(thd, select_lex->db, lex->name,
&lex->create_info,
@ -3296,6 +3317,14 @@ end_with_restore_list:
break;
/* Skip first table, which is the table we are inserting in */
select_lex->context.table_list= first_table->next_local;
if (!thd->locked_tables &&
!(need_start_waiting= !wait_if_global_read_lock(thd, 0, 1)))
{
res= 1;
break;
}
res= mysql_insert(thd, all_tables, lex->field_list, lex->many_values,
lex->update_list, lex->value_list,
lex->duplicates, lex->ignore);
@ -3319,6 +3348,14 @@ end_with_restore_list:
select_lex->options|= SELECT_NO_UNLOCK;
unit->set_limit(select_lex);
if (! thd->locked_tables &&
! (need_start_waiting= ! wait_if_global_read_lock(thd, 0, 1)))
{
res= 1;
break;
}
if (!(res= open_and_lock_tables(thd, all_tables)))
{
/* Skip first table, which is the table we are inserting in */
@ -3395,6 +3432,14 @@ end_with_restore_list:
break;
DBUG_ASSERT(select_lex->offset_limit == 0);
unit->set_limit(select_lex);
if (!thd->locked_tables &&
!(need_start_waiting= !wait_if_global_read_lock(thd, 0, 1)))
{
res= 1;
break;
}
res = mysql_delete(thd, all_tables, select_lex->where,
&select_lex->order_list,
unit->select_limit_cnt, select_lex->options,
@ -3408,6 +3453,13 @@ end_with_restore_list:
(TABLE_LIST *)thd->lex->auxilliary_table_list.first;
multi_delete *result;
if (!thd->locked_tables &&
!(need_start_waiting= !wait_if_global_read_lock(thd, 0, 1)))
{
res= 1;
break;
}
if ((res= multi_delete_precheck(thd, all_tables)))
break;
@ -4974,10 +5026,22 @@ end_with_restore_list:
if (lex->sql_command != SQLCOM_CALL && lex->sql_command != SQLCOM_EXECUTE &&
uc_update_queries[lex->sql_command]<2)
thd->row_count_func= -1;
DBUG_RETURN(res || thd->net.report_error);
goto end;
error:
DBUG_RETURN(1);
res= TRUE;
end:
if (need_start_waiting)
{
/*
Release the protection against the global read lock and wake
everyone, who might want to set a global read lock.
*/
start_waiting_global_read_lock(thd);
}
DBUG_RETURN(res || thd->net.report_error);
}