Re: Possible race condition in oom-killer

From	Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Newsgroups	linux.kernel
Subject	Re: Possible race condition in oom-killer
Date	2017-07-28 15:20 +0200
Message-ID	<u8dln-4dP-3@gated-at.bofh.it> (permalink)
References	<u8cIF-3Kl-3@gated-at.bofh.it> <u8cIF-3Kl-1@gated-at.bofh.it> <u8dbI-4ad-17@gated-at.bofh.it> <u8dbJ-4ad-25@gated-at.bofh.it>
Organization	linux.* mail to news gateway

Show all headers | View raw

Michal Hocko wrote:
> > 4578 is consuming memory as mlocked pages. But the OOM reaper cannot reclaim
> > mlocked pages (i.e. can_madv_dontneed_vma() returns false due to VM_LOCKED), can it?
> 
> You are absolutely right. I am pretty sure I've checked mlocked counter
> as the first thing but that must be from one of the earlier oom reports.
> My fault I haven't checked it in the critical one
> 
> [  365.267347] oom_reaper: reaped process 4578 (oom02), now anon-rss:131559616kB, file-rss:0kB, shmem-rss:0kB
> [  365.282658] oom_reaper: reaped process 4583 (oom02), now anon-rss:131561664kB, file-rss:0kB, shmem-rss:0kB
> 
> and the above screemed about the fact I was just completely blind.
> 
> mlock pages handling is on my todo list for quite some time already but
> I didn't get around it to implement that. mlock code is very tricky.

task_will_free_mem(current) in out_of_memory() returning false due to
MMF_OOM_SKIP already set allowed each thread sharing that mm to select a new
OOM victim. If task_will_free_mem(current) in out_of_memory() did not return
false, threads sharing MMF_OOM_SKIP mm would not have selected new victims
to the level where all OOM killable processes are killed and calls panic().

Thread

Re: Possible race condition in oom-killer Michal Hocko <mhocko@kernel.org> - 2017-07-28 14:40 +0200
  Re: Possible race condition in oom-killer Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp> - 2017-07-28 15:10 +0200
    Re: Possible race condition in oom-killer Michal Hocko <mhocko@kernel.org> - 2017-07-28 15:10 +0200
      Re: Possible race condition in oom-killer Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp> - 2017-07-28 15:20 +0200
        Re: Possible race condition in oom-killer Michal Hocko <mhocko@kernel.org> - 2017-07-28 15:40 +0200
          Re: Possible race condition in oom-killer Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp> - 2017-07-28 16:00 +0200
            Re: Possible race condition in oom-killer Michal Hocko <mhocko@kernel.org> - 2017-07-28 16:10 +0200
              Re: Possible race condition in oom-killer Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp> - 2017-07-29 06:40 +0200
  Re: Possible race condition in oom-killer Michal Hocko <mhocko@kernel.org> - 2017-07-28 16:20 +0200

csiph-web