Spurious lock_wait_timeout_thread wakeup in lock_wait_suspend_thread()

[Laurynas Biveinis]

This is a copy of https://bugs.mysql.com/bug.php?id=72123:

"When a query thread has to wait on a rec or table lock it goes to sleep by calling lock_wait_suspend_thread(). In this function before starting the wait we do the following:

        /* Wake the lock timeout monitor thread, if it is suspended */

        os_event_set(lock_sys->timeout_event);

This is totally unnecessary because lock timeout monitor thread wakes up every second to release waiting threads. There is no need to wake it up when we are going to start a wait."

and

"On a related note, there are various other wakeup calls for lock_monitor thread in the code. These calls are actually meant for srv_monitor_thread as they relate to printing monitor output and lock monitor has nothing to do with printing stuff."

[Laurynas Biveinis (laurynas-biveinis)]

https://github.com/percona/percona-server/pull/1830

[Shahriyar Rzayev (rzayev-sehriyar)]

Percona now uses JIRA for bug reports so this bug report is migrated to: https://jira.percona.com/browse/PS-2504