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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.

mysql-test/t/query_cache_debug.test:
  Only wait for a single debug signal at a time as the signal state
  is global.
sql/sql_cache.cc:
  Do not execute the debug sync point if the thread has no associated
  THD session. This scenario happens for federated threads.
This commit is contained in:
Davi Arnaut 2010-10-08 09:16:20 -03:00
commit 15ccca1d55
3 changed files with 39 additions and 13 deletions
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22
sql/sql_cache.cc
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@ -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)