On Thu 26-05-16 23:30:06, Tetsuo Handa wrote: > Michal Hocko wrote: > > diff --git a/mm/oom_kill.c b/mm/oom_kill.c > > index 5bb2f7698ad7..0e33e912f7e4 100644 > > --- a/mm/oom_kill.c > > +++ b/mm/oom_kill.c > > @@ -820,6 +820,13 @@ void oom_kill_process(struct oom_control *oc, struct > > task_struct *p, > > task_unlock(victim); > > > > /* > > + * skip expensive iterations over all tasks if we know that there > > + * are no users outside of threads in the same thread group > > + */ > > + if (atomic_read(&mm->mm_users) <= get_nr_threads(victim)) > > + goto oom_reap; > > Is this really safe? Isn't it possible that victim thread's thread group has > more than atomic_read(&mm->mm_users) threads which are past exit_mm() and > blocked > at exit_task_work() which are before __exit_signal() from release_task() from > exit_notify()?
You are right. The race window between exit_mm and __exit_signal is really large. I thought about == check instead but that wouldn't work for the same reason, dang, it looked so promissing. Scratch this patch then. -- Michal Hocko SUSE Labs
