#At file:///export/home/tmp/oysteing/mysql/mysql-6.0-backup/
2693 Oystein Grovlen 2008-09-05
Bug#39152 Intermittent debug_sync time-outs in backup tests
Timeouts have occurred due to race conditions in debug_sync
Make sure all accesses to debug_sync_global.ds_signal is protected
by mutex.
modified:
sql/debug_sync.cc
per-file messages:
sql/debug_sync.cc
Make sure all accesses to debug_sync_global.ds_signal is protected
by mutex.
=== modified file 'sql/debug_sync.cc'
=== modified file 'sql/debug_sync.cc'
--- a/sql/debug_sync.cc 2008-06-30 19:40:33 +0000
+++ b/sql/debug_sync.cc 2008-09-05 09:00:57 +0000
@@ -711,7 +711,9 @@
ds_control->ds_active= 0;
/* Clear the global signal. */
+ pthread_mutex_lock(&debug_sync_global.ds_mutex);
debug_sync_global.ds_signal.length(0);
+ pthread_mutex_unlock(&debug_sync_global.ds_mutex);
DBUG_VOID_RETURN;
}
@@ -1511,7 +1513,11 @@
if (opt_debug_sync_timeout)
{
- static char on[]= "ON - current signal: '";
+ static char on[]= "ON - current signal: '";
+
+ // Ensure exclusive access to debug_sync_global.ds_signal
+ pthread_mutex_lock(&debug_sync_global.ds_mutex);
+
size_t lgt= (sizeof(on) /* includes '\0' */ +
debug_sync_global.ds_signal.length() + 1 /* for '\'' */);
char *vend;
@@ -1527,6 +1533,7 @@
*(vptr++)= '\'';
*vptr= '\0'; /* We have one byte reserved for the worst case. */
}
+ pthread_mutex_unlock(&debug_sync_global.ds_mutex);
}
else
value= strmake_root(thd->mem_root, STRING_WITH_LEN("OFF"));
@@ -1582,6 +1589,13 @@
thd_proc_info(thd, proc_info.c_ptr());
}
+ /*
+ Take mutex to ensure that only one thread access
+ debug_sync_global.ds_signal at a time. Need to take mutex for
+ read access too, to create a memory barrier in order to avoid that
+ threads just reads an old cached version of the signal.
+ */
+ pthread_mutex_lock(&debug_sync_global.ds_mutex);
if (action->signal.length())
{
/* Copy the signal to the global variable. */
@@ -1606,7 +1620,6 @@
int error= 0;
struct timespec abstime;
- pthread_mutex_lock(&debug_sync_global.ds_mutex);
/*
We don't use enter_cond()/exit_cond(). They do not save old
mutex and cond. This would prohibit the use of DEBUG_SYNC
@@ -1670,6 +1683,11 @@
pthread_mutex_unlock(&thd->mysys_var->mutex);
} /* end if (action->wait_for.length()) */
+ else
+ {
+ // Make sure to realease mutex also when there is no WAIT_FOR
+ pthread_mutex_unlock(&debug_sync_global.ds_mutex);
+ }
} /* end if (action->execute) */
