On Tue 16-02-16 20:11:24, Tetsuo Handa wrote: > Michal Hocko wrote: > > Unless we are under global OOM then this doesn't matter much because the > > allocation request should succeed at some point in time and memcg > > charges are bypassed for tasks with pending fatal signals. So we can > > make a forward progress. > > Hmm, then I wonder how memcg OOM livelock occurs. Anyway, OK for now. > > But current OOM reaper forgot a protection for list item "double add" bug. > Precisely speaking, this is not a OOM reaper's bug. [...] > For oom_kill_allocating_task = 1 case (despite the name, it still tries to kill > children first), Yes this is a long term behavior and I cannot say I would be happy about that because it clearly breaks the defined semantic. > the OOM killer does not wait for OOM victim to clear TIF_MEMDIE > because select_bad_process() is not called. Therefore, if an OOM victim fails to > terminate because the OOM reaper failed to reap enough memory, the kernel is > flooded with OOM killer messages trying to kill that stuck victim (with OOM > reaper lockup due to list corruption). Hmmm, I didn't consider this possibility. For now I would simply disable oom_reaper for sysctl_oom_kill_allocating_task. oom_kill_allocating_task needs some more changes IMO. a) we shouldn't kill children as a heuristic b) we should go and panic if the current task is TIF_MEMDIE already because that means that we cannot do anything about OOM. But I think this should be handled separately. Whould be the following acceptable for now? --- diff --git a/mm/oom_kill.c b/mm/oom_kill.c index 7e9953a64489..357cee067950 100644 --- a/mm/oom_kill.c +++ b/mm/oom_kill.c @@ -678,7 +678,14 @@ void oom_kill_process(struct oom_control *oc, struct task_struct *p, unsigned int victim_points = 0; static DEFINE_RATELIMIT_STATE(oom_rs, DEFAULT_RATELIMIT_INTERVAL, DEFAULT_RATELIMIT_BURST); - bool can_oom_reap = true; + bool can_oom_reap; + + /* + * oom_kill_allocating_task doesn't follow normal OOM exclusion + * and so the same task might enter oom_kill_process which oom_reaper + * cannot handle currently. + */ + can_oom_reap = !sysctl_oom_kill_allocating_task; /* * If the task is already exiting, don't alarm the sysadmin or kill -- Michal Hocko SUSE Labs -- 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>