From: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp> To: firstname.lastname@example.org Cc: email@example.com, firstname.lastname@example.org, email@example.com, firstname.lastname@example.org, email@example.com, firstname.lastname@example.org, email@example.com, firstname.lastname@example.org, email@example.com Subject: Re: mm, oom_reaper: How to handle race with oom_killer_disable() ? Date: Wed, 22 Jun 2016 06:47:48 +0900 [thread overview] Message-ID: <201606220647.GGD48936.LMtJVOOOFFQFHS@I-love.SAKURA.ne.jp> (raw) In-Reply-To: <20160621174617.GA27527@dhcp22.suse.cz> Michal Hocko wrote: > On Wed 22-06-16 00:32:29, Tetsuo Handa wrote: > > Michal Hocko wrote: > [...] > > > Hmm, what about the following instead. It is rather a workaround than a > > > full flaged fix but it seems much more easier and shouldn't introduce > > > new issues. > > > > Yes, I think that will work. But I think below patch (marking signal_struct > > to ignore TIF_MEMDIE instead of clearing TIF_MEMDIE from task_struct) on top of > > current linux.git will implement no-lockup requirement. No race is possible unlike > > "[PATCH 10/10] mm, oom: hide mm which is shared with kthread or global init". > > Not really. Because without the exit_oom_victim from oom_reaper you have > no guarantee that the oom_killer_disable will ever return. I have > mentioned that in the changelog. There is simply no guarantee the oom > victim will ever reach exit_mm->exit_oom_victim. Why? Since any allocation after setting oom_killer_disabled = true will be forced to fail, nobody will be blocked on waiting for memory allocation. Thus, the TIF_MEMDIE tasks will eventually reach exit_mm->exit_oom_victim, won't it? The only possibility that the TIF_MEMDIE tasks won't reach exit_mm->exit_oom_victim is __GFP_NOFAIL allocations failing to make forward progress even after ALLOC_NO_WATERMARKS is used. But that is a different problem which I think we can call panic() when __GFP_NOFAIL allocations failed after setting oom_killer_disabled = true.
next prev parent reply other threads:[~2016-06-21 21:49 UTC|newest] Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top 2016-06-10 14:23 Tetsuo Handa 2016-06-13 11:19 ` Michal Hocko 2016-06-21 8:31 ` Michal Hocko 2016-06-21 11:03 ` Tetsuo Handa 2016-06-21 11:46 ` Michal Hocko 2016-06-21 13:27 ` Michal Hocko 2016-06-21 15:32 ` Tetsuo Handa 2016-06-21 17:46 ` Michal Hocko 2016-06-21 21:47 ` Tetsuo Handa [this message] 2016-06-22 6:40 ` Michal Hocko 2016-06-22 6:50 ` Michal Hocko 2016-06-22 10:57 ` Tetsuo Handa 2016-06-22 12:08 ` Michal Hocko 2016-06-22 12:15 ` Michal Hocko
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