Hi, this is the v4 version of the patchse. Previous version was posted http://lkml.kernel.org/r/1464945404-30157-1-git-send-email-mhocko@xxxxxxxxxx It's been mostly my screwups during the rebase that were fixed and patch 10 reworked. The following 10 patches should put some order to very rare cases of mm shared between processes and make the paths which bypass the oom killer oom reapable and therefore much more reliable finally. Even though mm shared outside of thread group is rare (either vforked tasks for a short period, use_mm by kernel threads or exotic thread model of clone(CLONE_VM) without CLONE_SIGHAND) it is better to cover them. Not only it makes the current oom killer logic quite hard to follow and reason about it can lead to weird corner cases. E.g. it is possible to select an oom victim which shares the mm with unkillable process or bypass the oom killer even when other processes sharing the mm are still alive and other weird cases. Patch 1 drops bogus task_lock and mm check from oom_{score_}adj_write. This can be considered a bug fix with a low impact as nobody has noticed for years. Patch 2 drops sighand lock because it is not needed anymore as pointed by Oleg. Patch 3 is a clean up of oom_score_adj handling and a preparatory work for later patches. Patch 4 enforces oom_adj_score to be consistent between processes sharing the mm to behave consistently with the regular thread groups. This can be considered a user visible behavior change because one thread group updating oom_score_adj will affect others which share the same mm via clone(CLONE_VM). I argue that this should be acceptable because we already have the same behavior for threads in the same thread group and sharing the mm without signal struct is just a different model of threading. This is probably the most controversial part of the series, I would like to find some consensus here. There were some suggestions to hook some counter/oom_score_adj into the mm_struct but I feel that this is not necessary right now and we can rely on proc handler + oom_kill_process to DTRT. I can be convinced otherwise but I strongly think that whatever we do the userspace has to have a way to see the current oom priority as consistently as possible. Patch 5 makes sure that no vforked task is selected if it is sharing the mm with oom unkillable task. Patch 6 ensures that all user tasks sharing the mm are killed which in turn makes sure that all oom victims are oom reapable. Patch 7 guarantees that task_will_free_mem will always imply reapable bypass of the oom killer. Patch 8 is new in this version and it addresses an issue pointed out by 0-day OOM report where an oom victim was reaped several times. Patch 9 puts an upper bound on how many times oom_reaper tries to reap a task and hides it from the oom killer to move on when no progress can be made. This will give an upper bound to how long an oom_reapable task can block the oom killer from selecting another victim if the oom_reaper is not able to reap the victim. Patch 10 tries to plug the (hopefully) last hole when we can still lock up when the oom victim is shared with oom unkillable tasks (kthreads and global init). We just try to be best effort in that case and rather fallback to kill something else than risk a lockup. I believe that timeout based heurisitcs are no longer really needed after this series. We still have some room for improvements, though. I would like to explore ways how to remove kthreads (use_mm) special case. It shouldn't be that hard, we just have to teach the page fault handler to recognize oom victim mm and enforce EFAULT for kthreads which have borrowed that mm. The patchset is based on the current mmotm tree (mmotm-2016-06-08-15-25). I would really appreciate a deep review as this area is full of land mines but I hope I've made the code much cleaner with less kludges. I have pushed the patchset to my git tree git://git.kernel.org/pub/scm/linux/kernel/git/mhocko/mm.git to branch attempts/process-share-mm-oom-sanitization Michal Hocko (10): proc, oom: drop bogus task_lock and mm check proc, oom: drop bogus sighand lock proc, oom_adj: extract oom_score_adj setting into a helper mm, oom_adj: make sure processes sharing mm have same view of oom_score_adj mm, oom: skip vforked tasks from being selected mm, oom: kill all tasks sharing the mm mm, oom: fortify task_will_free_mem mm, oom: task_will_free_mem should skip oom_reaped tasks mm, oom_reaper: do not attempt to reap a task more than twice mm, oom: hide mm which is shared with kthread or global init fs/proc/base.c | 185 ++++++++++++++++++++++++---------------------- include/linux/mm.h | 2 + include/linux/oom.h | 26 +------ include/linux/sched.h | 27 +++++++ mm/memcontrol.c | 4 +- mm/oom_kill.c | 201 ++++++++++++++++++++++++++++++++++---------------- 6 files changed, 266 insertions(+), 179 deletions(-) -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. 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