Re: mm: deadlock between get_online_cpus/pcpu_alloc

From	Mel Gorman <mgorman@techsingularity.net>
Newsgroups	linux.kernel
Subject	Re: mm: deadlock between get_online_cpus/pcpu_alloc
Date	2017-02-07 17:30 +0100
Message-ID	<t8gOt-5dy-7@gated-at.bofh.it> (permalink)
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On Tue, Feb 07, 2017 at 04:34:59PM +0100, Michal Hocko wrote:
> > But we do not care about the whole cpu hotplug code. The only part we
> > really do care about is the race inside drain_pages_zone and that will
> > run in an atomic context on the specific CPU.
> > 
> > You are absolutely right that using the mutex is safe as well but the
> > hotplug path is already littered with locks and adding one more to the
> > picture doesn't sound great to me. So I would really like to not use a
> > lock if that is possible and safe (with a big fat comment of course).
> 
> And with the full changelog. I hope I haven't missed anything this time.
> ---
> From 8c6af3116520251cc4ec2213f0a4ed2544bb4365 Mon Sep 17 00:00:00 2001
> From: Michal Hocko <mhocko@suse.com>
> Date: Tue, 7 Feb 2017 16:08:35 +0100
> Subject: [PATCH] mm, page_alloc: do not depend on cpu hotplug locks inside the
>  allocator
> 
> <SNIP>
>
> Reported-by: Dmitry Vyukov <dvyukov@google.com>
> Signed-off-by: Michal Hocko <mhocko@suse.com>

Not that I can think of. It's almost identical to the diff I posted with
the exception of the mutex in the cpu hotplug teardown path. I agree that
in the current implementation that it should be unnecessary even if I
thought it would be more robust against any other hotplug churn.

Acked-by: Mel Gorman <mgorman@techsingularity.net>

-- 
Mel Gorman
SUSE Labs

Thread

Re: mm: deadlock between get_online_cpus/pcpu_alloc Dmitry Vyukov <dvyukov@google.com> - 2017-02-06 20:20 +0100
  Re: mm: deadlock between get_online_cpus/pcpu_alloc Mel Gorman <mgorman@techsingularity.net> - 2017-02-06 23:10 +0100
    Re: mm: deadlock between get_online_cpus/pcpu_alloc Michal Hocko <mhocko@kernel.org> - 2017-02-07 09:50 +0100
      Re: mm: deadlock between get_online_cpus/pcpu_alloc Vlastimil Babka <vbabka@suse.cz> - 2017-02-07 10:30 +0100
        Re: mm: deadlock between get_online_cpus/pcpu_alloc Mel Gorman <mgorman@techsingularity.net> - 2017-02-07 10:50 +0100
        Re: mm: deadlock between get_online_cpus/pcpu_alloc Michal Hocko <mhocko@kernel.org> - 2017-02-07 11:00 +0100
        Re: mm: deadlock between get_online_cpus/pcpu_alloc Mel Gorman <mgorman@techsingularity.net> - 2017-02-07 11:50 +0100
          Re: mm: deadlock between get_online_cpus/pcpu_alloc Mel Gorman <mgorman@techsingularity.net> - 2017-02-07 12:20 +0100
      Re: mm: deadlock between get_online_cpus/pcpu_alloc Mel Gorman <mgorman@techsingularity.net> - 2017-02-07 10:50 +0100
        Re: mm: deadlock between get_online_cpus/pcpu_alloc Vlastimil Babka <vbabka@suse.cz> - 2017-02-07 11:00 +0100
          Re: mm: deadlock between get_online_cpus/pcpu_alloc Michal Hocko <mhocko@kernel.org> - 2017-02-07 11:10 +0100
          Re: mm: deadlock between get_online_cpus/pcpu_alloc Mel Gorman <mgorman@techsingularity.net> - 2017-02-07 11:30 +0100
            Re: mm: deadlock between get_online_cpus/pcpu_alloc Michal Hocko <mhocko@kernel.org> - 2017-02-07 11:40 +0100
              Re: mm: deadlock between get_online_cpus/pcpu_alloc Mel Gorman <mgorman@techsingularity.net> - 2017-02-07 12:40 +0100
                Re: mm: deadlock between get_online_cpus/pcpu_alloc Michal Hocko <mhocko@kernel.org> - 2017-02-07 12:50 +0100
                Re: mm: deadlock between get_online_cpus/pcpu_alloc Vlastimil Babka <vbabka@suse.cz> - 2017-02-07 13:00 +0100
                Re: mm: deadlock between get_online_cpus/pcpu_alloc Michal Hocko <mhocko@kernel.org> - 2017-02-07 13:10 +0100
                Re: mm: deadlock between get_online_cpus/pcpu_alloc Michal Hocko <mhocko@kernel.org> - 2017-02-07 13:40 +0100
                Re: mm: deadlock between get_online_cpus/pcpu_alloc Vlastimil Babka <vbabka@suse.cz> - 2017-02-07 13:50 +0100
                Re: mm: deadlock between get_online_cpus/pcpu_alloc Michal Hocko <mhocko@kernel.org> - 2017-02-07 13:50 +0100
                Re: mm: deadlock between get_online_cpus/pcpu_alloc Vlastimil Babka <vbabka@suse.cz> - 2017-02-07 15:00 +0100
                Re: mm: deadlock between get_online_cpus/pcpu_alloc Mel Gorman <mgorman@techsingularity.net> - 2017-02-07 15:00 +0100
                Re: mm: deadlock between get_online_cpus/pcpu_alloc Michal Hocko <mhocko@kernel.org> - 2017-02-07 15:20 +0100
                Re: mm: deadlock between get_online_cpus/pcpu_alloc Michal Hocko <mhocko@kernel.org> - 2017-02-07 16:40 +0100
                Re: mm: deadlock between get_online_cpus/pcpu_alloc Mel Gorman <mgorman@techsingularity.net> - 2017-02-07 17:30 +0100
                Re: mm: deadlock between get_online_cpus/pcpu_alloc Michal Hocko <mhocko@kernel.org> - 2017-02-07 17:50 +0100
                Re: mm: deadlock between get_online_cpus/pcpu_alloc Christoph Lameter <cl@linux.com> - 2017-02-07 18:00 +0100
                Re: mm: deadlock between get_online_cpus/pcpu_alloc Thomas Gleixner <tglx@linutronix.de> - 2017-02-07 23:30 +0100
                Re: mm: deadlock between get_online_cpus/pcpu_alloc Michal Hocko <mhocko@kernel.org> - 2017-02-08 08:40 +0100
                Re: mm: deadlock between get_online_cpus/pcpu_alloc Thomas Gleixner <tglx@linutronix.de> - 2017-02-08 13:10 +0100
                Re: mm: deadlock between get_online_cpus/pcpu_alloc Michal Hocko <mhocko@kernel.org> - 2017-02-08 13:30 +0100
                Re: mm: deadlock between get_online_cpus/pcpu_alloc Mel Gorman <mgorman@techsingularity.net> - 2017-02-08 13:50 +0100
                Re: mm: deadlock between get_online_cpus/pcpu_alloc Mel Gorman <mgorman@techsingularity.net> - 2017-02-08 15:10 +0100
                Re: mm: deadlock between get_online_cpus/pcpu_alloc Peter Zijlstra <peterz@infradead.org> - 2017-02-08 18:00 +0100
                Re: mm: deadlock between get_online_cpus/pcpu_alloc Thomas Gleixner <tglx@linutronix.de> - 2017-02-08 15:10 +0100
                Re: mm: deadlock between get_online_cpus/pcpu_alloc Christoph Lameter <cl@linux.com> - 2017-02-08 16:30 +0100
                Re: mm: deadlock between get_online_cpus/pcpu_alloc Christoph Lameter <cl@linux.com> - 2017-02-08 17:30 +0100
                Re: mm: deadlock between get_online_cpus/pcpu_alloc Thomas Gleixner <tglx@linutronix.de> - 2017-02-08 19:40 +0100
                Re: mm: deadlock between get_online_cpus/pcpu_alloc Christoph Lameter <cl@linux.com> - 2017-02-09 04:20 +0100
                Re: mm: deadlock between get_online_cpus/pcpu_alloc Thomas Gleixner <tglx@linutronix.de> - 2017-02-09 12:50 +0100
                Re: mm: deadlock between get_online_cpus/pcpu_alloc Christoph Lameter <cl@linux.com> - 2017-02-09 15:10 +0100
                Re: mm: deadlock between get_online_cpus/pcpu_alloc Thomas Gleixner <tglx@linutronix.de> - 2017-02-09 16:40 +0100
                Re: mm: deadlock between get_online_cpus/pcpu_alloc Christoph Lameter <cl@linux.com> - 2017-02-09 16:50 +0100
                Re: mm: deadlock between get_online_cpus/pcpu_alloc Thomas Gleixner <tglx@linutronix.de> - 2017-02-09 17:20 +0100
                Re: mm: deadlock between get_online_cpus/pcpu_alloc Christoph Lameter <cl@linux.com> - 2017-02-09 18:30 +0100
                Re: mm: deadlock between get_online_cpus/pcpu_alloc Thomas Gleixner <tglx@linutronix.de> - 2017-02-09 18:50 +0100
                Re: mm: deadlock between get_online_cpus/pcpu_alloc Michal Hocko <mhocko@kernel.org> - 2017-02-09 20:20 +0100
                Re: mm: deadlock between get_online_cpus/pcpu_alloc Christoph Lameter <cl@linux.com> - 2017-02-10 19:10 +0100
                Re: mm: deadlock between get_online_cpus/pcpu_alloc Michal Hocko <mhocko@kernel.org> - 2017-02-08 18:40 +0100
                Re: mm: deadlock between get_online_cpus/pcpu_alloc Christoph Lameter <cl@linux.com> - 2017-02-08 16:10 +0100
                Re: mm: deadlock between get_online_cpus/pcpu_alloc Tejun Heo <tj@kernel.org> - 2017-02-07 18:10 +0100
                Re: mm: deadlock between get_online_cpus/pcpu_alloc Michal Hocko <mhocko@kernel.org> - 2017-02-07 21:40 +0100
                Re: mm: deadlock between get_online_cpus/pcpu_alloc Mel Gorman <mgorman@techsingularity.net> - 2017-02-07 14:10 +0100
                Re: mm: deadlock between get_online_cpus/pcpu_alloc Michal Hocko <mhocko@kernel.org> - 2017-02-07 14:50 +0100
    Re: mm: deadlock between get_online_cpus/pcpu_alloc Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp> - 2017-02-07 12:30 +0100
  Re: mm: deadlock between get_online_cpus/pcpu_alloc Michal Hocko <mhocko@kernel.org> - 2017-02-07 09:50 +0100
  Re: mm: deadlock between get_online_cpus/pcpu_alloc Thomas Gleixner <tglx@linutronix.de> - 2017-02-07 23:40 +0100

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