On Thu, Jul 27, 2017 at 04:45:44PM +0200, Michal Hocko wrote: > On Thu 27-07-17 23:01:05, Tetsuo Handa wrote: > > Michal Hocko wrote: > > > diff --git a/mm/memcontrol.c b/mm/memcontrol.c > > > index 544d47e5cbbd..86a48affb938 100644 > > > --- a/mm/memcontrol.c > > > +++ b/mm/memcontrol.c > > > @@ -1896,7 +1896,7 @@ static int try_charge(struct mem_cgroup *memcg, gfp_t gfp_mask, > > > * bypass the last charges so that they can exit quickly and > > > * free their memory. > > > */ > > > - if (unlikely(test_thread_flag(TIF_MEMDIE) || > > > + if (unlikely(tsk_is_oom_victim(current) || > > > fatal_signal_pending(current) || > > > current->flags & PF_EXITING)) > > > goto force; > > > > Did we check http://lkml.kernel.org/r/20160909140508.GO4844@xxxxxxxxxxxxxx ? > > OK, so your concern was > > > Does this test_thread_flag(TIF_MEMDIE) (or tsk_is_oom_victim(current)) make sense? > > > > If current thread is OOM-killed, SIGKILL must be pending before arriving at > > do_exit() and PF_EXITING must be set after arriving at do_exit(). > > > But I can't find locations which do memory allocation between clearing > > SIGKILL and setting PF_EXITING. > > I can't find them either and maybe there are none. But why do we care > in this particular patch which merely replaces TIF_MEMDIE check by > tsk_is_oom_victim? The code will surely not become less valid. If > you believe this check is redundant then send a patch with the clear > justification. But I would say, at least from the robustness point of > view I would just keep it there. We do not really have any control on > what happens between clearing signals and setting PF_EXITING. I agree, this check is probably redundant, but it really makes no difference, let's keep it bullet-proof. If we care about performance here, we can rearrange the checks: if (unlikely(fatal_signal_pending(current) || current->flags & PF_EXITING) || tsk_is_oom_victim(current)) goto force; Roman -- 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>
