#At file:///home/thek/Development/cpp/mysqlbzr/51-bug43748/ based on revid:joro@stripped
2822 Kristofer Pettersson 2009-04-02
Bug#43758 Query cache can lock up threads in 'freeing items' state
Early patch submitted for discussion.
It is possible for more than one thread to enter the condition
in query_cache_insert(), but the condition predicate is to
signal one thread each time the cache status changes between
the following states: {NO_FLUSH_IN_PROGRESS,FLUSH_IN_PROGRESS,
TABLE_FLUSH_IN_PROGRESS}
Consider three threads THD1, THD2, THD3
THD2: select ... => Got a writer in ::store_query
THD3: select ... => Got a writer in ::store_query
THD1: flush tables => qc status= FLUSH_IN_PROGRESS;
new writers are blocked.
THD2: select ... => Still got a writer and enters cond in
query_cache_insert
THD3: select ... => Still got a writer and enters cond in
query_cache_insert
THD1: flush tables => finished and signal status change.
THD2: select ... => Wakes up and completes the insert.
THD3: select ... => Happily waiting for better times. Why hurry?
A solution to this situation is to use a broadcast on the thread
group which contain result set writers.
Note about the test case:
* If the thread policy in Query_cache::wait_while_flush_is_in_progress
is set to RELEASE_ONE_ON_EACH_SIGNAL then the test case will hang.
This should show the existence of a problem before the patch.
* Two thread groups used to avoid using broadcast where it isn't needed.
If it worth having two groups? Is substituting signal for broadcast enough?
added:
mysql-test/r/query_cache_debug2.result
mysql-test/t/query_cache_debug2.test
modified:
sql/sql_cache.cc
sql/sql_cache.h
=== added file 'mysql-test/r/query_cache_debug2.result'
--- a/mysql-test/r/query_cache_debug2.result 1970-01-01 00:00:00 +0000
+++ b/mysql-test/r/query_cache_debug2.result 2009-04-02 09:16:11 +0000
@@ -0,0 +1,96 @@
+FLUSH STATUS;
+SET GLOBAL query_cache_type=DEMAND;
+SET GLOBAL query_cache_size= 1024*768;
+DROP TABLE IF EXISTS t1,t2,t3,t4,t5;
+CREATE TABLE t1 (a VARCHAR(100)) engine=InnoDB;
+CREATE TABLE t2 (a VARCHAR(100)) engine=InnoDB;
+CREATE TABLE t3 (a VARCHAR(100)) engine=InnoDB;
+CREATE TABLE t4 (a VARCHAR(100)) engine=InnoDB;
+CREATE TABLE t5 (a VARCHAR(100)) engine=InnoDB;
+INSERT INTO t1 VALUES ('aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa'),('bbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbb');
+INSERT INTO t2 VALUES ('aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa'),('bbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbb');
+INSERT INTO t3 VALUES ('aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa'),('bbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbb');
+INSERT INTO t4 VALUES ('aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa'),('bbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbb');
+INSERT INTO t5 VALUES ('aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa'),('bbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbb');
+**
+** Load Query Cache with a result set and one table.
+**
+SELECT SQL_CACHE * FROM t1;
+a
+aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa
+bbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbb
+*************************************************************************
+** We want to accomplish the following state:
+** - Query cache status: TABLE_FLUSH_IN_PROGRESS
+** - THD1: invalidate_table_internal (iterating query blocks)
+** - THD2: query_cache_insert (cond_wait)
+** - THD3: query_cache_insert (cond_wait)
+** - No thread should be holding the structure_guard_mutex.
+**
+** First step is to place a DELETE-statement on the debug hook just
+** before the mutex lock in invalidate_table_internal.
+** This will allow new result sets to be written into the QC.
+**
+SET SESSION debug='+d,wait_in_query_cache_invalidate1';
+SET SESSION debug='+d,wait_in_query_cache_invalidate2';
+DELETE FROM t1 WHERE a like '%a%';;
+** Assert that the expect process status is obtained.
+**
+** 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 SESSION debug='+d,wait_in_query_cache_insert';
+SELECT SQL_CACHE * FROM t2 UNION SELECT * FROM t3;
+** On THD3: Insert another result into the cache and block on the same
+** debug hook.
+SET SESSION debug='+d,wait_in_query_cache_insert';
+SELECT SQL_CACHE * FROM t4 UNION SELECT * FROM t5;;
+** Assert that the two SELECT-stmt threads to reach the hook.
+**
+**
+** Signal the DELETE thread, THD1, to continue. It will enter the mutex
+** lock and set query cache status to TABLE_FLUSH_IN_PROGRESS and then
+** unlock the mutex before stopping on the next debug hook.
+SELECT id FROM information_schema.processlist WHERE state='wait_in_query_cache_invalidate1' LIMIT 1 INTO @flush_thread_id;
+KILL QUERY @flush_thread_id;
+** Assert that we reach the next debug hook.
+**
+** Signal the remaining debug hooks blocking THD2 and THD3.
+** The threads will grab the guard mutex enter the wait condition and
+** and finally release the mutex. The threads will continue to wait
+** until a broadcast signal reaches them causing both threads to
+** come alive and check the condition.
+SELECT id FROM information_schema.processlist WHERE state='wait_in_query_cache_insert' LIMIT 1 INTO @thread_id;
+KILL QUERY @thread_id;
+SELECT id FROM information_schema.processlist WHERE state='wait_in_query_cache_insert' LIMIT 1 INTO @thread_id;
+KILL QUERY @thread_id;
+**
+** Finally signal the DELETE statement on THD1 one last time.
+** The stmt will complete the query cache invalidation and return
+** cache status to NO_FLUSH_IN_PROGRESS. On the status change
+** One signal will be sent to the thread group waiting for executing
+** invalidations and a broadcast signal will be sent to the thread
+** group holding result set writers.
+SELECT id FROM information_schema.processlist WHERE state='wait_in_query_cache_invalidate2' LIMIT 1 INTO @flush_thread_id;
+KILL QUERY @flush_thread_id;
+**
+*************************************************************************
+** No tables should be locked
+a
+aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa
+bbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbb
+DELETE FROM t1;
+DELETE FROM t2;
+DELETE FROM t3;
+a
+aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa
+bbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbb
+DELETE FROM t4;
+DELETE FROM t5;
+SET GLOBAL query_cache_size= 0;
+# Restore defaults
+RESET QUERY CACHE;
+FLUSH STATUS;
+DROP TABLE t1,t2,t3,t4,t5;
+SET GLOBAL query_cache_size= DEFAULT;
+SET GLOBAL query_cache_type= DEFAULT;
=== added file 'mysql-test/t/query_cache_debug2.test'
--- a/mysql-test/t/query_cache_debug2.test 1970-01-01 00:00:00 +0000
+++ b/mysql-test/t/query_cache_debug2.test 2009-04-02 09:16:11 +0000
@@ -0,0 +1,133 @@
+--source include/have_innodb.inc
+#
+# BUG#43748
+#
+FLUSH STATUS;
+SET GLOBAL query_cache_type=DEMAND;
+SET GLOBAL query_cache_size= 1024*768;
+--disable_warnings
+DROP TABLE IF EXISTS t1,t2,t3,t4,t5;
+--enable_warnings
+CREATE TABLE t1 (a VARCHAR(100)) engine=InnoDB;
+CREATE TABLE t2 (a VARCHAR(100)) engine=InnoDB;
+CREATE TABLE t3 (a VARCHAR(100)) engine=InnoDB;
+CREATE TABLE t4 (a VARCHAR(100)) engine=InnoDB;
+CREATE TABLE t5 (a VARCHAR(100)) engine=InnoDB;
+
+INSERT INTO t1 VALUES ('aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa'),('bbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbb');
+INSERT INTO t2 VALUES ('aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa'),('bbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbb');
+INSERT INTO t3 VALUES ('aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa'),('bbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbb');
+INSERT INTO t4 VALUES ('aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa'),('bbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbb');
+INSERT INTO t5 VALUES ('aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa'),('bbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbb');
+
+connect (con1, localhost, root, ,test);
+connect (con2, localhost, root, ,test);
+connect (con3, localhost, root, ,test);
+
+connection con3;
+--echo **
+--echo ** Load Query Cache with a result set and one table.
+--echo **
+SELECT SQL_CACHE * FROM t1;
+--echo *************************************************************************
+--echo ** We want to accomplish the following state:
+--echo ** - Query cache status: TABLE_FLUSH_IN_PROGRESS
+--echo ** - THD1: invalidate_table_internal (iterating query blocks)
+--echo ** - THD2: query_cache_insert (cond_wait)
+--echo ** - THD3: query_cache_insert (cond_wait)
+--echo ** - No thread should be holding the structure_guard_mutex.
+--echo **
+--echo ** First step is to place a DELETE-statement on the debug hook just
+--echo ** before the mutex lock in invalidate_table_internal.
+--echo ** This will allow new result sets to be written into the QC.
+--echo **
+SET SESSION debug='+d,wait_in_query_cache_invalidate1';
+SET SESSION debug='+d,wait_in_query_cache_invalidate2';
+--send DELETE FROM t1 WHERE a like '%a%';
+
+connection default;
+--echo ** Assert that the expect process status is obtained.
+LET $wait_condition= SELECT COUNT(*)= 1 FROM information_schema.processlist WHERE state= 'wait_in_query_cache_invalidate1';
+--source include/wait_condition.inc
+-- echo **
+
+connection con1;
+--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 SESSION debug='+d,wait_in_query_cache_insert';
+--send SELECT SQL_CACHE * FROM t2 UNION SELECT * FROM t3
+
+connection con2;
+--echo ** On THD3: Insert another result into the cache and block on the same
+--echo ** debug hook.
+SET SESSION debug='+d,wait_in_query_cache_insert';
+--send SELECT SQL_CACHE * FROM t4 UNION SELECT * FROM t5;
+
+connection default;
+--echo ** Assert that the two SELECT-stmt threads to reach the hook.
+LET $wait_condition= SELECT COUNT(*)= 2 FROM information_schema.processlist WHERE state= 'wait_in_query_cache_insert';
+--source include/wait_condition.inc
+--echo **
+--echo **
+
+--echo ** Signal the DELETE thread, THD1, to continue. It will enter the mutex
+--echo ** lock and set query cache status to TABLE_FLUSH_IN_PROGRESS and then
+--echo ** unlock the mutex before stopping on the next debug hook.
+SELECT id FROM information_schema.processlist WHERE state='wait_in_query_cache_invalidate1' LIMIT 1 INTO @flush_thread_id;
+KILL QUERY @flush_thread_id;
+--echo ** Assert that we reach the next debug hook.
+LET $wait_condition= SELECT COUNT(*)= 1 FROM information_schema.processlist WHERE state= 'wait_in_query_cache_invalidate2';
+--source include/wait_condition.inc
+
+--echo **
+--echo ** Signal the remaining debug hooks blocking THD2 and THD3.
+--echo ** The threads will grab the guard mutex enter the wait condition and
+--echo ** and finally release the mutex. The threads will continue to wait
+--echo ** until a broadcast signal reaches them causing both threads to
+--echo ** come alive and check the condition.
+SELECT id FROM information_schema.processlist WHERE state='wait_in_query_cache_insert' LIMIT 1 INTO @thread_id;
+KILL QUERY @thread_id;
+SELECT id FROM information_schema.processlist WHERE state='wait_in_query_cache_insert' LIMIT 1 INTO @thread_id;
+KILL QUERY @thread_id;
+--echo **
+--echo ** Finally signal the DELETE statement on THD1 one last time.
+--echo ** The stmt will complete the query cache invalidation and return
+--echo ** cache status to NO_FLUSH_IN_PROGRESS. On the status change
+--echo ** One signal will be sent to the thread group waiting for executing
+--echo ** invalidations and a broadcast signal will be sent to the thread
+--echo ** group holding result set writers.
+SELECT id FROM information_schema.processlist WHERE state='wait_in_query_cache_invalidate2' LIMIT 1 INTO @flush_thread_id;
+KILL QUERY @flush_thread_id;
+
+--echo **
+--echo *************************************************************************
+--echo ** No tables should be locked
+connection con1;
+reap;
+DELETE FROM t1;
+DELETE FROM t2;
+DELETE FROM t3;
+
+connection con2;
+reap;
+DELETE FROM t4;
+DELETE FROM t5;
+
+connection con3;
+reap;
+
+connection default;
+disconnect con1;
+disconnect con2;
+disconnect con3;
+SET GLOBAL query_cache_size= 0;
+
+connection default;
+--echo # Restore defaults
+RESET QUERY CACHE;
+FLUSH STATUS;
+DROP TABLE t1,t2,t3,t4,t5;
+SET GLOBAL query_cache_size= DEFAULT;
+SET GLOBAL query_cache_type= DEFAULT;
+exit;
=== modified file 'sql/sql_cache.cc'
--- a/sql/sql_cache.cc 2009-03-17 20:29:24 +0000
+++ b/sql/sql_cache.cc 2009-04-02 09:16:11 +0000
@@ -705,7 +705,7 @@ void query_cache_init_query(NET *net)
void query_cache_insert(NET *net, const char *packet, ulong length)
{
DBUG_ENTER("query_cache_insert");
-
+ THD *thd= current_thd;
/* See the comment on double-check locking usage above. */
if (net->query_cache_query == 0)
DBUG_VOID_RETURN;
@@ -715,13 +715,16 @@ void query_cache_insert(NET *net, const
STRUCT_LOCK(&query_cache.structure_guard_mutex);
bool interrupt;
- query_cache.wait_while_table_flush_is_in_progress(&interrupt);
+ query_cache.wait_while_table_flush_is_in_progress(&interrupt,
+ Query_cache::RELEASE_ALL_CONCURRENTLY);
+
if (interrupt)
{
+ thd_proc_info(thd, thd->query);
STRUCT_UNLOCK(&query_cache.structure_guard_mutex);
DBUG_VOID_RETURN;
}
-
+ thd_proc_info(thd, thd->query);
Query_cache_block *query_block= (Query_cache_block*)net->query_cache_query;
if (!query_block)
{
@@ -776,10 +779,11 @@ void query_cache_abort(NET *net)
/* See the comment on double-check locking usage above. */
if (net->query_cache_query == 0)
DBUG_VOID_RETURN;
-
+ thd_proc_info(thd, "query cache aborting");
STRUCT_LOCK(&query_cache.structure_guard_mutex);
bool interrupt;
- query_cache.wait_while_table_flush_is_in_progress(&interrupt);
+ query_cache.wait_while_table_flush_is_in_progress(&interrupt,
+ Query_cache::RELEASE_ALL_CONCURRENTLY);
if (interrupt)
{
STRUCT_UNLOCK(&query_cache.structure_guard_mutex);
@@ -814,6 +818,7 @@ void query_cache_end_of_result(THD *thd)
Query_cache_block *query_block;
DBUG_ENTER("query_cache_end_of_result");
+ thd_proc_info(thd, "query cache end of result");
/* See the comment on double-check locking usage above. */
if (thd->net.query_cache_query == 0)
DBUG_VOID_RETURN;
@@ -835,7 +840,8 @@ void query_cache_end_of_result(THD *thd)
STRUCT_LOCK(&query_cache.structure_guard_mutex);
bool interrupt;
- query_cache.wait_while_table_flush_is_in_progress(&interrupt);
+ query_cache.wait_while_table_flush_is_in_progress(&interrupt,
+ Query_cache::RELEASE_ALL_CONCURRENTLY);
if (interrupt)
{
STRUCT_UNLOCK(&query_cache.structure_guard_mutex);
@@ -988,7 +994,7 @@ ulong Query_cache::resize(ulong query_ca
STRUCT_LOCK(&structure_guard_mutex);
m_cache_status= Query_cache::NO_FLUSH_IN_PROGRESS;
- pthread_cond_signal(&COND_cache_status_changed);
+ signal_all_queues_waiting_for_status_change();
if (new_query_cache_size)
DBUG_EXECUTE("check_querycache",check_integrity(1););
STRUCT_UNLOCK(&structure_guard_mutex);
@@ -1668,8 +1674,10 @@ void Query_cache::invalidate(THD *thd, c
The structure_guard_mutex will in any case be locked.
*/
-void Query_cache::wait_while_table_flush_is_in_progress(bool *interrupt)
+void Query_cache::wait_while_table_flush_is_in_progress(bool *interrupt,
+ Query_cache::Wait_policy policy)
{
+ THD *thd= current_thd;
while (is_flushing())
{
/*
@@ -1678,16 +1686,35 @@ void Query_cache::wait_while_table_flush
*/
if (m_cache_status == Query_cache::FLUSH_IN_PROGRESS)
{
+ thd_proc_info(thd, "skip query cache; flush in progress");
*interrupt= TRUE;
return;
}
+ pthread_cond_t *queue;
+ switch(policy)
+ {
+ case Query_cache::RELEASE_ALL_CONCURRENTLY:
+ DBUG_PRINT("Query_cache",("Wait for pthread broadcast"));
+ queue= &COND_cache_status_changed_broadcast;
+ break;
+ case Query_cache::RELEASE_ONE_ON_EACH_SIGNAL:
+ DBUG_PRINT("Query_cache",("Wait for pthread signal"));
+ queue= &COND_cache_status_changed;
+ break;
+ default:
+ DBUG_ASSERT(0);
+ }
+
/*
If a table flush is in progress; wait on cache status to change.
*/
- if (m_cache_status == Query_cache::TABLE_FLUSH_IN_PROGRESS)
- pthread_cond_wait(&COND_cache_status_changed, &structure_guard_mutex);
+ thd_proc_info(thd, "waiting on query cache table flush");
+ if (m_cache_status == Query_cache::TABLE_FLUSH_IN_PROGRESS) {
+ pthread_cond_wait(queue, &structure_guard_mutex);
+ }
}
*interrupt= FALSE;
+ thd_proc_info(thd, "query cache");
}
@@ -1702,7 +1729,8 @@ void Query_cache::invalidate(char *db)
STRUCT_LOCK(&structure_guard_mutex);
bool interrupt;
- wait_while_table_flush_is_in_progress(&interrupt);
+ wait_while_table_flush_is_in_progress(&interrupt,
+ Query_cache::RELEASE_ONE_ON_EACH_SIGNAL);
if (interrupt)
{
STRUCT_UNLOCK(&structure_guard_mutex);
@@ -1787,6 +1815,8 @@ void Query_cache::invalidate_by_MyISAM_f
void Query_cache::flush()
{
DBUG_ENTER("Query_cache::flush");
+ DBUG_EXECUTE_IF("wait_in_query_cache_flush1",
+ debug_wait_for_kill("wait_in_query_cache_flush1"););
STRUCT_LOCK(&structure_guard_mutex);
if (query_cache_size > 0)
{
@@ -1817,7 +1847,8 @@ void Query_cache::pack(ulong join_limit,
bool interrupt;
STRUCT_LOCK(&structure_guard_mutex);
- wait_while_table_flush_is_in_progress(&interrupt);
+ wait_while_table_flush_is_in_progress(&interrupt,
+ Query_cache::RELEASE_ONE_ON_EACH_SIGNAL);
if (interrupt)
{
STRUCT_UNLOCK(&structure_guard_mutex);
@@ -2129,7 +2160,8 @@ void Query_cache::flush_cache()
*/
m_cache_status= Query_cache::FLUSH_IN_PROGRESS;
STRUCT_UNLOCK(&structure_guard_mutex);
-
+ DBUG_EXECUTE_IF("wait_in_query_cache_flush2",
+ debug_wait_for_kill("wait_in_query_cache_flush2"););
my_hash_reset(&queries);
while (queries_blocks != 0)
{
@@ -2139,7 +2171,7 @@ void Query_cache::flush_cache()
STRUCT_LOCK(&structure_guard_mutex);
m_cache_status= Query_cache::NO_FLUSH_IN_PROGRESS;
- pthread_cond_signal(&COND_cache_status_changed);
+ signal_all_queues_waiting_for_status_change();
}
/*
@@ -2591,8 +2623,11 @@ void Query_cache::invalidate_table(THD *
void Query_cache::invalidate_table(THD *thd, uchar * key, uint32 key_length)
{
bool interrupt;
+ DBUG_EXECUTE_IF("wait_in_query_cache_invalidate1",
+ debug_wait_for_kill("wait_in_query_cache_invalidate1"); );
STRUCT_LOCK(&structure_guard_mutex);
- wait_while_table_flush_is_in_progress(&interrupt);
+ wait_while_table_flush_is_in_progress(&interrupt,
+ Query_cache::RELEASE_ONE_ON_EACH_SIGNAL);
if (interrupt)
{
STRUCT_UNLOCK(&structure_guard_mutex);
@@ -2607,7 +2642,8 @@ void Query_cache::invalidate_table(THD *
*/
m_cache_status= Query_cache::TABLE_FLUSH_IN_PROGRESS;
STRUCT_UNLOCK(&structure_guard_mutex);
-
+ DBUG_EXECUTE_IF("wait_in_query_cache_invalidate2",
+ debug_wait_for_kill("wait_in_query_cache_invalidate2"); );
if (query_cache_size > 0)
invalidate_table_internal(thd, key, key_length);
@@ -2618,7 +2654,7 @@ void Query_cache::invalidate_table(THD *
net_real_write might be waiting on a change on the m_cache_status
variable.
*/
- pthread_cond_signal(&COND_cache_status_changed);
+ signal_all_queues_waiting_for_status_change();
STRUCT_UNLOCK(&structure_guard_mutex);
}
@@ -2634,6 +2670,7 @@ void Query_cache::invalidate_table(THD *
void
Query_cache::invalidate_table_internal(THD *thd, uchar *key, uint32 key_length)
{
+ DBUG_ENTER("Query_cache::invalidate_table_internal");
Query_cache_block *table_block=
(Query_cache_block*)hash_search(&tables, key, key_length);
if (table_block)
@@ -2641,6 +2678,7 @@ Query_cache::invalidate_table_internal(T
Query_cache_block_table *list_root= table_block->table(0);
invalidate_query_block_list(thd, list_root);
}
+ DBUG_VOID_RETURN;
}
/**
=== modified file 'sql/sql_cache.h'
--- a/sql/sql_cache.h 2008-07-24 13:41:55 +0000
+++ b/sql/sql_cache.h 2009-04-02 09:16:11 +0000
@@ -272,11 +272,25 @@ public:
private:
+ /**
+ This condition queue is signaled when ever query cache status changes.
+ Threads waiting in this queue will reset, flush or invalidate
+ either a part of the cache or all of the cache. The threads will be
+ executed in a serialized order.
+ */
pthread_cond_t COND_cache_status_changed;
+ /**
+ This condition queue is broadcasted when ever query cache status changes.
+ Threads waiting in this queue are writing a result set to the cache and
+ should be executed concurrently when ever the lock is dropped.
+ */
+ pthread_cond_t COND_cache_status_changed_broadcast;
enum Cache_status { NO_FLUSH_IN_PROGRESS, FLUSH_IN_PROGRESS,
TABLE_FLUSH_IN_PROGRESS };
+ enum Wait_policy { RELEASE_ONE_ON_EACH_SIGNAL, RELEASE_ALL_CONCURRENTLY };
+
Cache_status m_cache_status;
void free_query_internal(Query_cache_block *point);
@@ -380,7 +394,22 @@ protected:
Query_cache_block *pprev);
my_bool join_results(ulong join_limit);
- void wait_while_table_flush_is_in_progress(bool *interrupt);
+ void wait_while_table_flush_is_in_progress(bool *interrupt,
+ Query_cache::Wait_policy policy);
+
+ void signal_all_queues_waiting_for_status_change(void)
+ {
+ /*
+ Release on thread waiting on a status change
+ */
+ pthread_cond_signal(&COND_cache_status_changed);
+
+ /*
+ Release all threads waiting on a status change
+ */
+ pthread_cond_broadcast(&COND_cache_status_changed_broadcast);
+ }
+
/*
Following function control structure_guard_mutex
Attachment: [text/bzr-bundle] bzr/kristofer.pettersson@sun.com-20090402091611-w0fn9p0u51artzz3.bundle
| Thread |
|---|
| • bzr commit into mysql-5.1-bugteam branch (kristofer.pettersson:2822)Bug#43758 | Kristofer Pettersson | 2 Apr |
