On Fri 14-11-14 15:14:19, Tejun Heo wrote: > On Wed, Nov 12, 2014 at 07:58:48PM +0100, Michal Hocko wrote: > > Hi, > > here is another take at OOM vs. PM freezer interaction fixes/cleanups. > > First three patches are fixes for an unlikely cases when OOM races with > > the PM freezer which should be closed completely finally. The last patch > > is a simple code enhancement which is not needed strictly speaking but > > it is nice to have IMO. > > > > Both OOM killer and PM freezer are quite subtle so I hope I haven't > > missing anything. Any feedback is highly appreciated. I am also > > interested about feedback for the used approach. To be honest I am not > > really happy about spreading TIF_MEMDIE checks into freezer (patch 1) > > but I didn't find any other way for detecting OOM killed tasks. > > I really don't get why this is structured this way. Can't you just do > the following? Well, I liked how simple this was and localized at the only place which matters. When I was thinking about a solution which you are describing below it was more complicated and more subtle (e.g. waiting for an OOM victim might be tricky if it stumbles over a lock which is held by a frozen thread which uses try_to_freeze_unsafe). Anyway I gave it another try and will post the two patches as a reply to this email. I hope the both interface and implementation is cleaner. > 1. Freeze all freezables. Don't worry about PF_MEMDIE. > > 2. Disable OOM killer. This should be contained in the OOM killer > proper. Lock out the OOM killer and disable it. > > 3. At this point, we know that no one will create more freezable > threads and no new process will be OOM kliled. Wait till there's > no process w/ PF_MEMDIE set. > > There's no reason to lock out or disable OOM killer while the system > is not in the quiescent state, which is a big can of worms. Bring > down the system to the quiescent state, disable the OOM killer and > then drain PF_MEMDIEs. -- Michal Hocko SUSE Labs -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>