On Thu 02-06-16 21:20:03, Tetsuo Handa wrote: [...] > Also, dmesg.xz in the crash report http://lkml.kernel.org/r/20160601080209.GA7190@yexl-desktop > includes an interesting race. > [...] > The consecutive oom_reaper message on the same thread > > ---------- > [ 82.706724] oom_reaper: reaped process 3914 (trinity-c0), now anon-rss:0kB, file-rss:0kB, shmem-rss:26488kB > [ 82.715540] oom_reaper: reaped process 3914 (trinity-c0), now anon-rss:0kB, file-rss:0kB, shmem-rss:26900kB > [ 82.717662] oom_reaper: reaped process 3914 (trinity-c0), now anon-rss:0kB, file-rss:0kB, shmem-rss:26900kB > [ 82.725804] oom_reaper: reaped process 3914 (trinity-c0), now anon-rss:0kB, file-rss:0kB, shmem-rss:27296kB > [ 82.739091] oom_reaper: reaped process 3914 (trinity-c0), now anon-rss:0kB, file-rss:0kB, shmem-rss:28148kB > ---------- > > suggests that it repeated race that trinity-c0 called out_of_memory() > and hit the shortcut > > if (current->mm && > (fatal_signal_pending(current) || task_will_free_mem(current))) { > mark_oom_victim(current); > try_oom_reaper(current); > return true; > } > > and got TIF_MEMDIE and woke up the OOM reaper. But the OOM reaper started > oom_reap_task() and cleared TIF_MEMDIE from trinity-c0 BEFORE trinity-c0 > tries to allocate using ALLOC_NO_WATERMARKS via TIF_MEMDIE. > > As a result, trinity-c0 was unable to use ALLOC_NO_WATERMARKS and had to call > out_of_memory() again. And again hit the shortcut and got TIF_MEMDIE and woke > up the OOM reaper, the OOM reaper cleared TIF_MEMDIE. So, this set TIF_MEMDIE > followed by clear TIF_MEMDIE repetition lasted for several times. Maybe we > should not try to clear TIF_MEMDIE from the OOM reaper. If we do not clear TIF_MEMDIE then we risk other issues. What we can do instead is to check for MMF_OOM_REAPED in task_will_free_mem and do not allow to bypass the oom killer. I will enahance the series which hammers that code path with that check. Thanks for pointing this out! -- 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>