From: Michal Hocko <mhocko@kernel.org> To: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp> Cc: akpm@linux-foundation.org, rientjes@google.com, hannes@cmpxchg.org, guro@fb.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH 2/2] mm: replace TIF_MEMDIE checks by tsk_is_oom_victim Date: Thu, 27 Jul 2017 16:45:44 +0200 [thread overview] Message-ID: <20170727144544.GC31031@dhcp22.suse.cz> (raw) In-Reply-To: <201707272301.EII82876.tOOJOFLMHFQSFV@I-love.SAKURA.ne.jp> 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@dhcp22.suse.cz ? 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. -- Michal Hocko SUSE Labs
WARNING: multiple messages have this Message-ID (diff)
From: Michal Hocko <mhocko@kernel.org> To: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp> Cc: akpm@linux-foundation.org, rientjes@google.com, hannes@cmpxchg.org, guro@fb.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH 2/2] mm: replace TIF_MEMDIE checks by tsk_is_oom_victim Date: Thu, 27 Jul 2017 16:45:44 +0200 [thread overview] Message-ID: <20170727144544.GC31031@dhcp22.suse.cz> (raw) In-Reply-To: <201707272301.EII82876.tOOJOFLMHFQSFV@I-love.SAKURA.ne.jp> 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@dhcp22.suse.cz ? 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. -- Michal Hocko SUSE Labs -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>
next prev parent reply other threads:[~2017-07-27 14:45 UTC|newest] Thread overview: 55+ messages / expand[flat|nested] mbox.gz Atom feed top 2017-07-27 9:03 [PATCH 0/2] mm, oom: do not grant oom victims full memory reserves access Michal Hocko 2017-07-27 9:03 ` Michal Hocko 2017-07-27 9:03 ` [PATCH 1/2] mm, oom: do not rely on TIF_MEMDIE for " Michal Hocko 2017-07-27 9:03 ` Michal Hocko 2017-08-01 15:30 ` Tetsuo Handa 2017-08-01 15:30 ` Tetsuo Handa 2017-08-01 16:52 ` Michal Hocko 2017-08-01 16:52 ` Michal Hocko 2017-08-02 6:10 ` Michal Hocko 2017-08-02 6:10 ` Michal Hocko 2017-08-03 1:39 ` Tetsuo Handa 2017-08-03 1:39 ` Tetsuo Handa 2017-08-03 7:06 ` Michal Hocko 2017-08-03 7:06 ` Michal Hocko 2017-08-03 8:03 ` Tetsuo Handa 2017-08-03 8:03 ` Tetsuo Handa 2017-08-03 8:21 ` Michal Hocko 2017-08-03 8:21 ` Michal Hocko 2017-08-02 8:29 ` [PATCH v2 " Michal Hocko 2017-08-02 8:29 ` Michal Hocko 2017-08-03 9:37 ` Mel Gorman 2017-08-03 9:37 ` Mel Gorman 2017-08-03 11:00 ` Michal Hocko 2017-08-03 11:00 ` Michal Hocko 2017-08-03 12:22 ` Mel Gorman 2017-08-03 12:22 ` Mel Gorman 2017-07-27 9:03 ` [PATCH 2/2] mm: replace TIF_MEMDIE checks by tsk_is_oom_victim Michal Hocko 2017-07-27 9:03 ` Michal Hocko 2017-07-27 14:01 ` Tetsuo Handa 2017-07-27 14:01 ` Tetsuo Handa 2017-07-27 14:08 ` Tetsuo Handa 2017-07-27 14:08 ` Tetsuo Handa 2017-07-27 14:18 ` Michal Hocko 2017-07-27 14:18 ` Michal Hocko 2017-07-27 14:45 ` Michal Hocko [this message] 2017-07-27 14:45 ` Michal Hocko 2017-07-27 14:55 ` Roman Gushchin 2017-07-27 14:55 ` Roman Gushchin 2017-07-29 8:33 ` kbuild test robot 2017-07-31 6:46 ` Michal Hocko 2017-07-31 6:46 ` Michal Hocko 2017-08-01 12:16 ` [PATCH 0/2] mm, oom: do not grant oom victims full memory reserves access Michal Hocko 2017-08-01 12:16 ` Michal Hocko 2017-08-01 12:23 ` Roman Gushchin 2017-08-01 12:23 ` Roman Gushchin 2017-08-01 12:29 ` Michal Hocko 2017-08-01 12:29 ` Michal Hocko 2017-08-01 12:42 ` Roman Gushchin 2017-08-01 12:42 ` Roman Gushchin 2017-08-01 12:54 ` Michal Hocko 2017-08-01 12:54 ` Michal Hocko 2017-08-07 14:21 ` Michal Hocko 2017-08-07 14:21 ` Michal Hocko 2017-08-10 7:50 [PATCH v2 " Michal Hocko 2017-08-10 7:50 ` [PATCH 2/2] mm: replace TIF_MEMDIE checks by tsk_is_oom_victim Michal Hocko 2017-08-10 7:50 ` Michal Hocko
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