Re: [PATCH] mm: respect the __GFP_NOWARN flag when warning about stalls

From	Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Newsgroups	linux.kernel
Subject	Re: [PATCH] mm: respect the __GFP_NOWARN flag when warning about stalls
Date	2017-09-13 16:20 +0200
Message-ID	<upgGd-8st-7@gated-at.bofh.it> (permalink)
References	<uosgp-nx-5@gated-at.bofh.it> <uoGt4-1Fz-11@gated-at.bofh.it> <upeuJ-6U2-7@gated-at.bofh.it> <upgmS-86m-11@gated-at.bofh.it> <upgwy-8oG-23@gated-at.bofh.it>
Organization	linux.* mail to news gateway

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Vlastimil Babka wrote:
> On 09/13/2017 03:54 PM, Tetsuo Handa wrote:
> > Michal Hocko wrote:
> >> Let's see what others think about this.
> > 
> > Whether __GFP_NOWARN should warn about stalls is not a topic to discuss.
> 
> It is the topic of this thread, which tries to address a concrete
> problem somebody has experienced. In that context, the rest of your
> concerns seem to me not related to this problem, IMHO.

I suggested replacing warn_alloc() with safe/useful one rather than tweaking
warn_alloc() about __GFP_NOWARN.

> 
> > I consider warn_alloc() for reporting stalls is broken. It fails to provide
> > backtrace of stalling location. For example, OOM lockup with oom_lock held
> > cannot be reported by warn_alloc(). It fails to provide readable output when
> > called concurrently. For example, concurrent calls can cause printk()/
> > schedule_timeout_killable() lockup with oom_lock held. printk() offloading is
> > not an option, for there will be situations where printk() offloading cannot
> > be used (e.g. queuing via printk() is faster than writing to serial consoles
> > which results in unreadable logs due to log_bug overflow).

Thread

[PATCH] mm: respect the __GFP_NOWARN flag when warning about  stalls Mikulas Patocka <mpatocka@redhat.com> - 2017-09-11 09:00 +0200
  Re: [PATCH] mm: respect the __GFP_NOWARN flag when warning about  stalls Michal Hocko <mhocko@kernel.org> - 2017-09-11 10:30 +0200
    Re: [PATCH] mm: respect the __GFP_NOWARN flag when warning about  stalls Mikulas Patocka <mpatocka@redhat.com> - 2017-09-12 01:40 +0200
      Re: [PATCH] mm: respect the __GFP_NOWARN flag when warning about  stalls Vlastimil Babka <vbabka@suse.cz> - 2017-09-12 09:20 +0200
        Re: [PATCH] mm: respect the __GFP_NOWARN flag when warning about stalls Shakeel Butt <shakeelb@google.com> - 2017-09-13 17:00 +0200
      Re: [PATCH] mm: respect the __GFP_NOWARN flag when warning about  stalls Michal Hocko <mhocko@kernel.org> - 2017-09-13 14:00 +0200
        Re: [PATCH] mm: respect the __GFP_NOWARN flag when warning about stalls Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp> - 2017-09-13 16:00 +0200
          Re: [PATCH] mm: respect the __GFP_NOWARN flag when warning about  stalls Vlastimil Babka <vbabka@suse.cz> - 2017-09-13 16:10 +0200
            Re: [PATCH] mm: respect the __GFP_NOWARN flag when warning about stalls Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp> - 2017-09-13 16:20 +0200
              Re: [PATCH] mm: respect the __GFP_NOWARN flag when warning about  stalls Michal Hocko <mhocko@kernel.org> - 2017-09-13 16:40 +0200

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