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Backport of revno: 2617.68.13

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Introduce a counter for protection against global read lock on thread level.

The functions for protection against global read lock sometimes need a local
variable to signal when the protection is set, and hence need to be released.
It would be better to control this behaviour via a counter on the THD struct,
telling how many times the protection has been claimed by the current thread.
A side-effect of the fix is that if protection is claimed twice for a thread,
only a simple increment is required for the second claim, instead of a
mutex-protected increment of the global variable protect_against_global_read_lock.
This commit is contained in:
Jon Olav Hauglid
2009-12-09 15:25:48 +01:00
parent 1642f67b40
commit 17252c3258
6 changed files with 115 additions and 32 deletions
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9
sql/sql_table.cc
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@@ -1780,16 +1780,16 @@ void write_bin_log(THD *thd, bool clear_error,
bool mysql_rm_table(THD *thd,TABLE_LIST *tables, my_bool if_exists,
my_bool drop_temporary)
{
bool error= FALSE, need_start_waiting= FALSE;
bool error;
Drop_table_error_handler err_handler(thd->get_internal_handler());
DBUG_ENTER("mysql_rm_table");
/* mark for close and remove all cached entries */
if (!drop_temporary)
{
if (!thd->locked_tables_mode &&
!(need_start_waiting= !wait_if_global_read_lock(thd, 0, 1)))
if (!thd->locked_tables_mode && wait_if_global_read_lock(thd, 0, 1))
DBUG_RETURN(TRUE);
}
@@ -1797,8 +1797,7 @@ bool mysql_rm_table(THD *thd,TABLE_LIST *tables, my_bool if_exists,
error= mysql_rm_table_part2(thd, tables, if_exists, drop_temporary, 0, 0);
thd->pop_internal_handler();
if (need_start_waiting)
if (thd->global_read_lock_protection > 0)
start_waiting_global_read_lock(thd);
if (error)