Fix a race condition introduced by r7004. We need to acquire the srv_sys->mutex

for all other cases where we release a suspended thread waiting on a lock other
than those released by the lock wait timer thread.

storage/innobase/include/trx0trx.h

@@ -647,6 +647,16 @@ struct trx_struct{
 					TRX_QUE_LOCK_WAIT, this points to
 					the lock request, otherwise this is
 					NULL */
+	ibool		lock_wait_timeout;
+					/* when this transaction is rolled
+					back because the lock wait timed out.
+					We use this flag to distinguish between
+					a wait time out detected by the lock
+				       	monitor thread vs other code paths. For
+					the former we already have the the
+					srv_sys->mutex locked. For the other
+					cases we need to acquire it explicitly
+					when releasing a suspended thread. */
 	ibool		was_chosen_as_deadlock_victim;
 					/* when the transaction decides to wait
 					for a lock, it sets this to FALSE;

storage/innobase/srv/srv0srv.c

@@ -1773,11 +1773,18 @@ srv_release_mysql_thread_if_suspended(
 {
 	ut_ad(mutex_own(&kernel_mutex));
 
-	if (thr->slot != NULL) {
-		ut_a(thr->slot->in_use);
+	if (!thr_get_trx(thr)->lock_wait_timeout) {
+		srv_sys_mutex_enter();
+	}
+
+	if (thr->slot != NULL && thr->slot->in_use && thr->slot->thr == thr) {
 
 		os_event_set(thr->slot->event);
 	}
+
+	if (!thr_get_trx(thr)->lock_wait_timeout) {
+		srv_sys_mutex_exit();
+	}
 }
 
 /******************************************************************//**
@@ -2320,8 +2327,11 @@ srv_lock_check_wait(
 
 				ut_a(trx->que_state == TRX_QUE_LOCK_WAIT);
 
-				lock_cancel_waiting_and_release(
-					trx->wait_lock);
+				trx->lock_wait_timeout = TRUE;
+
+				lock_cancel_waiting_and_release(trx->wait_lock);
+
+				trx->lock_wait_timeout = FALSE;
 			}
 
 			mutex_exit(&kernel_mutex);

storage/innobase/trx/trx0trx.c

@@ -189,6 +189,8 @@ trx_create(
 	trx->autoinc_locks = ib_vector_create(
 		mem_heap_create(sizeof(ib_vector_t) + sizeof(void*) * 4), 4);
 
+	trx->lock_wait_timeout = FALSE;
+
 	return(trx);
 }