Re: mm, oom_reaper: How to handle race with oom_killer_disable() ?

From	Michal Hocko <mhocko@kernel.org>
Newsgroups	linux.kernel
Subject	Re: mm, oom_reaper: How to handle race with oom_killer_disable() ?
Date	2016-06-22 14:10 +0200
Message-ID	<rMP8K-3bX-25@gated-at.bofh.it> (permalink)
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On Wed 22-06-16 19:57:17, Tetsuo Handa wrote:
> Michal Hocko wrote:
[...]
> > That being said I guess the patch to try_to_freeze_tasks after
> > oom_killer_disable should be simple enough to go for now and stable
> > trees and we can come up with something less hackish later. I do not
> > like the fact that oom_killer_disable doesn't act as a full "barrier"
> > anymore.
> > 
> > What do you think?
> 
> I'm OK with calling try_to_freeze_tasks(true) again for Linux 4.6 and 4.7 kernels.

OK, I will resend the patch CC Rafael and stable.
 
> But if free memory is little such that oom_killer_disable() can not expect TIF_MEMDIE
> threads to clear TIF_MEMDIE by themselves (and therefore has to depend on the OOM
> reaper to clear TIF_MEMDIE on behalf of them after the OOM reaper reaped some memory),
> subsequent operations would be as well blocked waiting for an operation which cannot
> make any forward progress because it cannot proceed with an allocation. Then,
> oom_killer_disable() returns false after some timeout (i.e. "do not try to suspend
> when the system is almost OOM") will be a safer reaction.

Yes that is exactly what I meant by "oom_killer_disable has to give up"
alternative. pm suspend already has a notion of timeout for back off
and oom_killer_disable can use wait_even_timeout. But let's do that
separately.

-- 
Michal Hocko
SUSE Labs

Thread

Re: mm, oom_reaper: How to handle race with oom_killer_disable() ? Michal Hocko <mhocko@kernel.org> - 2016-06-13 13:20 +0200
  Re: mm, oom_reaper: How to handle race with oom_killer_disable() ? Michal Hocko <mhocko@kernel.org> - 2016-06-21 10:40 +0200
    Re: mm, oom_reaper: How to handle race with oom_killer_disable() ? Michal Hocko <mhocko@kernel.org> - 2016-06-21 13:50 +0200
      Re: mm, oom_reaper: How to handle race with oom_killer_disable() ? Michal Hocko <mhocko@kernel.org> - 2016-06-21 15:30 +0200
        Re: mm, oom_reaper: How to handle race with oom_killer_disable() ? Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp> - 2016-06-21 17:40 +0200
          Re: mm, oom_reaper: How to handle race with oom_killer_disable() ? Michal Hocko <mhocko@kernel.org> - 2016-06-21 20:00 +0200
            Re: mm, oom_reaper: How to handle race with oom_killer_disable() ? Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp> - 2016-06-21 23:50 +0200
              Re: mm, oom_reaper: How to handle race with oom_killer_disable() ? Michal Hocko <mhocko@kernel.org> - 2016-06-22 08:50 +0200
                Re: mm, oom_reaper: How to handle race with oom_killer_disable() ? Michal Hocko <mhocko@kernel.org> - 2016-06-22 09:00 +0200
                Re: mm, oom_reaper: How to handle race with oom_killer_disable() ? Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp> - 2016-06-22 13:00 +0200
                Re: mm, oom_reaper: How to handle race with oom_killer_disable() ? Michal Hocko <mhocko@kernel.org> - 2016-06-22 14:10 +0200
                Re: mm, oom_reaper: How to handle race with oom_killer_disable() ? Michal Hocko <mhocko@kernel.org> - 2016-06-22 14:20 +0200
    Re: mm, oom_reaper: How to handle race with oom_killer_disable() ? Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp> - 2016-06-21 14:00 +0200

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