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Bug#56822: Add a thread state for sessions waiting on the query cache lock

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Only wait for a single debug signal at a time as the signal state
is global. Also, do not activate the query cache debug sync points
if the thread has no associated THD session.
This commit is contained in:
Davi Arnaut 2010-10-08 09:16:20 -03:00
parent 921fd52975
commit 657b157511
3 changed files with 39 additions and 13 deletions
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14
mysql-test/r/query_cache_debug.result
View File

@ -123,16 +123,20 @@ SET DEBUG_SYNC="now WAIT_FOR parked1_1";
** On THD2: Insert a result into the cache. This attempt will be blocked
** because of a debug hook placed just before the mutex lock after which
** the first part of the result set is written.
SET DEBUG_SYNC="wait_in_query_cache_insert SIGNAL parked2 WAIT_FOR go2";
SET DEBUG_SYNC="wait_in_query_cache_insert SIGNAL parked2 WAIT_FOR go2 EXECUTE 1";
SELECT SQL_CACHE * FROM t2 UNION SELECT * FROM t3;
=================================== Connection default
** Assert that the SELECT-stmt thread reaches the sync point.
SET DEBUG_SYNC="now WAIT_FOR parked2";
**
**
=================================== Connection thd3
** On THD3: Insert another result into the cache and block on the same
** debug hook.
SET DEBUG_SYNC="wait_in_query_cache_insert SIGNAL parked3 WAIT_FOR go3";
SELECT SQL_CACHE * FROM t4 UNION SELECT * FROM t5;;
SET DEBUG_SYNC="wait_in_query_cache_insert SIGNAL parked3 WAIT_FOR go3 EXECUTE 1";
SELECT SQL_CACHE * FROM t4 UNION SELECT * FROM t5;
=================================== Connection default
** Assert that the two SELECT-stmt threads to reach the hook.
SET DEBUG_SYNC="now WAIT_FOR parked2";
** Assert that the SELECT-stmt thread reaches the sync point.
SET DEBUG_SYNC="now WAIT_FOR parked3";
**
**

16
mysql-test/t/query_cache_debug.test
View File

@ -170,20 +170,26 @@ connection thd2;
--echo ** On THD2: Insert a result into the cache. This attempt will be blocked
--echo ** because of a debug hook placed just before the mutex lock after which
--echo ** the first part of the result set is written.
SET DEBUG_SYNC="wait_in_query_cache_insert SIGNAL parked2 WAIT_FOR go2";
SET DEBUG_SYNC="wait_in_query_cache_insert SIGNAL parked2 WAIT_FOR go2 EXECUTE 1";
--send SELECT SQL_CACHE * FROM t2 UNION SELECT * FROM t3
connection default;
--echo =================================== Connection default
--echo ** Assert that the SELECT-stmt thread reaches the sync point.
SET DEBUG_SYNC="now WAIT_FOR parked2";
--echo **
--echo **
connection thd3;
--echo =================================== Connection thd3
--echo ** On THD3: Insert another result into the cache and block on the same
--echo ** debug hook.
SET DEBUG_SYNC="wait_in_query_cache_insert SIGNAL parked3 WAIT_FOR go3";
--send SELECT SQL_CACHE * FROM t4 UNION SELECT * FROM t5;
SET DEBUG_SYNC="wait_in_query_cache_insert SIGNAL parked3 WAIT_FOR go3 EXECUTE 1";
--send SELECT SQL_CACHE * FROM t4 UNION SELECT * FROM t5
connection default;
--echo =================================== Connection default
--echo ** Assert that the two SELECT-stmt threads to reach the hook.
SET DEBUG_SYNC="now WAIT_FOR parked2";
--echo ** Assert that the SELECT-stmt thread reaches the sync point.
SET DEBUG_SYNC="now WAIT_FOR parked3";
--echo **
--echo **

22
sql/sql_cache.cc
View File

@ -384,6 +384,22 @@ TODO list:
#endif
/**
Macro that executes the requested action at a synchronization point
only if the thread has a associated THD session.
*/
#if defined(ENABLED_DEBUG_SYNC)
#define QC_DEBUG_SYNC(name) \
do { \
THD *thd= current_thd; \
if (thd) \
DEBUG_SYNC(thd, name); \
} while (0)
#else
#define QC_DEBUG_SYNC(name)
#endif
/**
Thread state to be used when the query cache lock needs to be acquired.
Sets the thread state name in the constructor, resets on destructor.
@ -879,7 +895,7 @@ Query_cache::insert(Query_cache_tls *query_cache_tls,
if (is_disabled() || query_cache_tls->first_query_block == NULL)
DBUG_VOID_RETURN;
DEBUG_SYNC(current_thd, "wait_in_query_cache_insert");
QC_DEBUG_SYNC("wait_in_query_cache_insert");
if (try_lock())
DBUG_VOID_RETURN;
@ -1975,7 +1991,7 @@ void Query_cache::flush()
if (is_disabled())
DBUG_VOID_RETURN;
DEBUG_SYNC(current_thd, "wait_in_query_cache_flush1");
QC_DEBUG_SYNC("wait_in_query_cache_flush1");
lock_and_suspend();
if (query_cache_size > 0)
@ -2315,7 +2331,7 @@ void Query_cache::free_cache()
void Query_cache::flush_cache()
{
DEBUG_SYNC(current_thd, "wait_in_query_cache_flush2");
QC_DEBUG_SYNC("wait_in_query_cache_flush2");
my_hash_reset(&queries);
while (queries_blocks != 0)