Hi, I have sent this pile as an RFC [1] previously and after some testing and discussion about an alternative approach [2] it seems this will plug the remaining holes which could lead to oom lockups for CONFIG_MMU and open doors to further improvements and cleanups. I have added few more patches since the last time. Patches 1 and 2 can be considered cleanups and I've taken them from Tetsuo's patchset [2]. Patch 3 is the core part of this series. It makes the mm of the oom victim persistent in signal struct so that the oom killer can rely purely on this mm rather than find_lock_task_mm which might not find any mm if all threads passed exit_mm. Patch 4 is a follow up fix noticed during testing. I could have folded it to the patch 3 but I guess both will be easier to review if they are separate. Patch 5 is a cleanup and it removes signal_struct::oom_victims which is no longer needed. Patch 6 makes oom_killer_disable full quiescent state barrier again. Patch 7 is a pure cleanup. Again taken from Tetsuo's series [2]. Patch 8 moves exit_oom_victim out of exit_mm to the end of do_exit. Patch 9 transforms vhost get_user/copy_from_user usage to oom reaper safe variant. There were some proposals how to provide a different API - e.g. a notification mechanism resp. processing SIGKILL from the kernel thread - but none of them was either lockless or easier and I really do not want to make further lock dependencies between oom killer and other kernel subsystems. I didn't get to test this part because I do not have much idea why. I would really appreciate help from Michael here. Patch 10 then allows to reap oom victim memory even when it is shared with a kthread via use_mm as the only problematic user is safe to after the previous patch. This leaves the only non-reapable case when the global init shares the mm with a different process (other than vfork) which I would consider exotic and slightly idiotic so I wouldn't lose sleep over it. After this series we should have guaranteed forward progress for the oom killer invocation for mmu arches AFAICS. It would be great if this could make it into 4.9. I would like to build on top of this and clean up the code even more. I would like to get rid of TIF_MEMDIE in the next step and make memory reserves access completely independent on the rest of the OOM killer logic. I have run this through the hammering tests mostly coming from Tetsuo and apart from the lockup fixed by the patch 4 and nothing popped out. The series is based on top of the mmotm (2016-07-22-15-51). Feedback is more than welcome. Thanks! [1] http://lkml.kernel.org/r/1467365190-24640-1-git-send-email-mhocko@xxxxxxxxxx [2] http://lkml.kernel.org/r/201607031135.AAH95347.MVOHQtFJFLOOFS@xxxxxxxxxxxxxxxxxxx Michal Hocko (7): oom: keep mm of the killed task available mm, oom: get rid of signal_struct::oom_victims kernel, oom: fix potential pgd_lock deadlock from __mmdrop oom, suspend: fix oom_killer_disable vs. pm suspend properly exit, oom: postpone exit_oom_victim to later vhost, mm: make sure that oom_reaper doesn't reap memory read by vhost oom, oom_reaper: allow to reap mm shared by the kthreads Tetsuo Handa (3): mm,oom_reaper: Reduce find_lock_task_mm() usage. mm,oom_reaper: Do not attempt to reap a task twice. mm, oom: enforce exit_oom_victim on current task drivers/vhost/scsi.c | 2 +- drivers/vhost/vhost.c | 18 +++--- include/linux/mm_types.h | 2 - include/linux/oom.h | 10 ++- include/linux/sched.h | 21 ++++++- include/linux/uaccess.h | 22 +++++++ include/linux/uio.h | 10 +++ kernel/exit.c | 5 +- kernel/fork.c | 7 +++ kernel/power/process.c | 17 +---- mm/mmu_context.c | 6 ++ mm/oom_kill.c | 161 +++++++++++++++++++++-------------------------- 12 files changed, 158 insertions(+), 123 deletions(-) -- 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>