On Fri, Dec 15, 2023 at 03:51:19PM +0100, Denis V. Lunev wrote: > On 12/15/23 14:48, Efim Shevrin wrote: > > *From:* Daniel P. Berrangé <berrange@xxxxxxxxxx> > > *Sent:* Friday, December 15, 2023 19:09 > > *To:* Efim Shevrin <efim.shevrin@xxxxxxxxxxxxx> > > *Cc:* devel@xxxxxxxxxxxxxxxxx <devel@xxxxxxxxxxxxxxxxx>; den@xxxxxxxxxx > > <den@xxxxxxxxxx> > > *Subject:* Re: [PATCH 3/3] rpc: Rework rpc notifications in main and > > side thread > > [You don't often get email from berrange@xxxxxxxxxx. Learn why this is > > important at https://aka.ms/LearnAboutSenderIdentification ] > > > > On Fri, Dec 15, 2023 at 02:32:19AM +0800, Fima Shevrin wrote: > > > RPC client implementation uses the following paradigm. The critical > > > section is organized via virObjectLock(client)/virObjectUnlock(client) > > > braces. Though this is potentially problematic as > > > main thread: side thread: > > > virObjectUnlock(client); > > > virObjectLock(client); > > > g_main_loop_quit(client->eventLoop); > > > virObjectUnlock(client); > > > g_main_loop_run(client->eventLoop); > > > > > > This means in particular that is the main thread is executing very long > > > request like VM migration, the wakeup from the side thread could be > > > stuck until the main request will be fully completed. > > > > Can you explain this in more detail, with call traces illustration > > for the two threads. You're not saying where the main thread is > > doing work with the 'client' lock hold for a long time. Generally > > the goal should be for the main thread to only hold the lock for > > a short time. Also if the side thread is already holding a reference > > on 'client', then potentially we should consider if it is possible > > to terminate the event loop without acquiring the mutex, as GMainLoop > > protects itself wrt concurrent usage already, provided all threads > > hold a reference directly or indirectly. > > At our opinion the problem here is missed wakeup from > the side thread to the main thread. Hmmm, what platform are you seeing problems on ? Are you still targetting a very old RHEL-7 platform ? I vaguely recall there are/weere some old glib bugs in the main loop with threads that could be applicable. With regards, Daniel -- |: https://berrange.com -o- https://www.flickr.com/photos/dberrange :| |: https://libvirt.org -o- https://fstop138.berrange.com :| |: https://entangle-photo.org -o- https://www.instagram.com/dberrange :| _______________________________________________ Devel mailing list -- devel@xxxxxxxxxxxxxxxxx To unsubscribe send an email to devel-leave@xxxxxxxxxxxxxxxxx
