On Wed 17-02-16 23:39:47, Tetsuo Handa wrote: > Michal Hocko wrote: > > On Wed 17-02-16 22:07:31, Tetsuo Handa wrote: > > > Michal Hocko wrote: > > > > On Wed 17-02-16 19:30:41, Tetsuo Handa wrote: > > > > > >From 22bd036766e70f0df38c38f3ecc226e857d20faf Mon Sep 17 00:00:00 2001 > > > > > From: Tetsuo Handa <penguin-kernel@xxxxxxxxxxxxxxxxxxx> > > > > > Date: Wed, 17 Feb 2016 16:30:59 +0900 > > > > > Subject: [PATCH 2/6] mm,oom: don't abort on exiting processes when selecting a victim. > > > > > > > > > > Currently, oom_scan_process_thread() returns OOM_SCAN_ABORT when there > > > > > is a thread which is exiting. But it is possible that that thread is > > > > > blocked at down_read(&mm->mmap_sem) in exit_mm() called from do_exit() > > > > > whereas one of threads sharing that memory is doing a GFP_KERNEL > > > > > allocation between down_write(&mm->mmap_sem) and up_write(&mm->mmap_sem) > > > > > (e.g. mmap()). Under such situation, the OOM killer does not choose a > > > > > victim, which results in silent OOM livelock problem. > > > > > > > > Again, such a thread/task will have fatal_signal_pending and so have > > > > access to memory reserves. So the text is slightly misleading imho. > > > > Sure if the memory reserves are depleted then we will not move on but > > > > then it is not clear whether the current patch helps either. > > > > > > I don't think so. > > > Please see http://lkml.kernel.org/r/201602151958.HCJ48972.FFOFOLMHSQVJtO@xxxxxxxxxxxxxxxxxxx . > > > > I have missed this one. Reading... > > > > Hmm, so you are not referring to OOM killed task but naturally exiting > > thread which is racing with the OOM killer. I guess you have a point > > there! Could you update the changelog with the above example and repost > > please? > > > Yes and I resent that patch as v2. > > I think that the same problem exists for any task_will_free_mem()-based > optimizations. Can we eliminate them because these optimized paths are not > handled by the OOM reaper which means that we have no means other than > "[PATCH 5/6] mm,oom: Re-enable OOM killer using timers." ? Well, only oom_kill_process usage of task_will_free_mem might be a problem because out_of_memory operates on the current task so it must be in the allocation path and access to memory reserves should help it to continue. Wrt. oom_kill_process this will be more tricky. I guess we want to teach oom_reaper to operate on such a task which would be a more robust solution than removing the check altogether. -- 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>