On Tue, 24 Apr 2018, Michal Hocko wrote: > > > > My patch has passed intensive testing on both x86 and powerpc, so I'll ask > > > > that it's pushed for 4.17-rc3. Many thanks to Tetsuo for the suggestion > > > > on calling __oom_reap_task_mm() from exit_mmap(). > > > > > > Yeah, but your patch does have a problem with blockable mmu notifiers > > > IIUC. > > > > What on earth are you talking about? exit_mmap() does > > mmu_notifier_release(). There are no blockable mmu notifiers. > > MMF_OOM_SKIP - remember? The thing that guarantees a forward progress. > So we cannot really depend on setting MMF_OOM_SKIP if a > mmu_notifier_release blocks for an excessive/unbounded amount of time. > If the thread is blocked in exit_mmap() because of mmu_notifier_release() then the oom reaper will eventually grab mm->mmap_sem (nothing holding it in exit_mmap()), return true, and oom_reap_task() will set MMF_OOM_SKIP. This is unchanged with the patch and is a completely separate issue. > Look I am not really interested in disussing this to death but it would > be really _nice_ if you could calm down a bit, stop fighting for the solution > you have proposed and ignore the feedback you are getting. > I assume we should spend more time considering the two untested patches you have sent, one of which killed 17 processes while a 8GB memory hog was exiting because the oom reaper couldn't grab mm->mmap_sem and set MMF_OOM_SKIP. > There are two things to care about here. Stop the race that can blow up > and do not regress MMF_OOM_SKIP guarantee. Can we please do that. My patch does both. Thanks.
