On Fri 08-08-14 17:46:38, Cong Wang wrote: > There is a race condition between OOM killer and freezer when > they try to operate on the same process, something like below: > > Process A Process B Process C > trigger oom > B=oom_scan_process_thread() > cgroup_freezer_freeze(B) > ... > try_to_freeze() > stay in D state > oom_kill_process(B) > > In this case, process A triggers OOM and kernel selects process B > as the victim, right before being killed process B was frozen by > process C therefore went to D state, then kernel sent SIGKILL but > it is already too late as process B will never care about pending > signals any more.
OK, so the system/memcg is still OOM and a new allocation/charge would trigger killer again, right? Then oom_scan_process_thread sees TIF_MEMDIE frozen task and thaw it so it can go away and die. So this shouldn't be a permanent state. Or am I missing something? > Fix this straightly by checking fatal pending signal > from OOM killer, so that the frozen process will recover itself > and then be killed finally. > > Cc: David Rientjes <rient...@google.com> > Cc: Michal Hocko <mho...@suse.cz> > Cc: "Rafael J. Wysocki" <r...@rjwysocki.net> > Cc: Tejun Heo <t...@kernel.org> > Cc: Andrew Morton <a...@linux-foundation.org> > Signed-off-by: Cong Wang <xiyou.wangc...@gmail.com> > --- > diff --git a/kernel/freezer.c b/kernel/freezer.c > index aa6a8aa..c6d189d 100644 > --- a/kernel/freezer.c > +++ b/kernel/freezer.c > @@ -68,7 +68,9 @@ bool __refrigerator(bool check_kthr_stop) > spin_lock_irq(&freezer_lock); > current->flags |= PF_FROZEN; > if (!freezing(current) || > - (check_kthr_stop && kthread_should_stop())) > + (check_kthr_stop && kthread_should_stop()) || > + (test_tsk_thread_flag(current, TIF_MEMDIE) && > + fatal_signal_pending(current))) > current->flags &= ~PF_FROZEN; > spin_unlock_irq(&freezer_lock); > -- Michal Hocko SUSE Labs -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
