Re: [PATCH 0/2 v8] oom: capture unreclaimable slab info in oom message

From	Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Newsgroups	linux.kernel
Subject	Re: [PATCH 0/2 v8] oom: capture unreclaimable slab info in oom message
Date	2017-09-28 22:00 +0200
Message-ID	<uuN8u-4KX-3@gated-at.bofh.it> (permalink)
References	<uusnn-8uO-3@gated-at.bofh.it> <uuyM9-4cw-17@gated-at.bofh.it> <uuL6G-3wn-15@gated-at.bofh.it>
Organization	linux.* mail to news gateway

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Yang Shi wrote:
> On 9/27/17 9:36 PM, Tetsuo Handa wrote:
> > On 2017/09/28 6:46, Yang Shi wrote:
> >> Changelog v7 -> v8:
> >> * Adopted Michal’s suggestion to dump unreclaim slab info when unreclaimable slabs amount > total user memory. Not only in oom panic path.
> > 
> > Holding slab_mutex inside dump_unreclaimable_slab() was refrained since V2
> > because there are
> > 
> > 	mutex_lock(&slab_mutex);
> > 	kmalloc(GFP_KERNEL);
> > 	mutex_unlock(&slab_mutex);
> > 
> > users. If we call dump_unreclaimable_slab() for non OOM panic path, aren't we
> > introducing a risk of crash (i.e. kernel panic) for regular OOM path?
> 
> I don't see the difference between regular oom path and oom path other 
> than calling panic() at last.
> 
> And, the slab dump may be called by panic path too, it is for both 
> regular and panic path.

Calling a function that might cause kerneloops immediately before calling panic()
would be tolerable, for the kernel will panic after all. But calling a function
that might cause kerneloops when there is no plan to call panic() is a bug.

> 
> Thanks,
> Yang
> 
> > 
> > We can try mutex_trylock() from dump_unreclaimable_slab() at best.
> > But it is still remaining unsafe, isn't it?
> > 
>

Thread

[PATCH 0/2 v8] oom: capture unreclaimable slab info in oom message "Yang Shi" <yang.s@alibaba-inc.com> - 2017-09-27 23:50 +0200
  [PATCH 2/2] mm: oom: show unreclaimable slab info when unreclaimable slabs > user memory "Yang Shi" <yang.s@alibaba-inc.com> - 2017-09-27 23:50 +0200
    Re: [PATCH 2/2] mm: oom: show unreclaimable slab info when unreclaimable  slabs > user memory Christopher Lameter <cl@linux.com> - 2017-10-01 08:20 +0200
  Re: [PATCH 0/2 v8] oom: capture unreclaimable slab info in oom  message Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp> - 2017-09-28 06:40 +0200
    Re: [PATCH 0/2 v8] oom: capture unreclaimable slab info in oom  message "Yang Shi" <yang.s@alibaba-inc.com> - 2017-09-28 19:50 +0200
      Re: [PATCH 0/2 v8] oom: capture unreclaimable slab info in oom message Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp> - 2017-09-28 22:00 +0200
        Re: [PATCH 0/2 v8] oom: capture unreclaimable slab info in oom  message "Yang Shi" <yang.s@alibaba-inc.com> - 2017-09-28 22:30 +0200
          Re: [PATCH 0/2 v8] oom: capture unreclaimable slab info in oom message Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp> - 2017-09-28 22:50 +0200
            Re: [PATCH 0/2 v8] oom: capture unreclaimable slab info in oom  message "Yang Shi" <yang.s@alibaba-inc.com> - 2017-09-30 00:20 +0200
              Re: [PATCH 0/2 v8] oom: capture unreclaimable slab info in oom message Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp> - 2017-09-30 13:10 +0200
                Re: [PATCH 0/2 v8] oom: capture unreclaimable slab info in oom  message "Yang Shi" <yang.s@alibaba-inc.com> - 2017-10-02 22:50 +0200
    Re: [PATCH 0/2 v8] oom: capture unreclaimable slab info in oom  message Michal Hocko <mhocko@kernel.org> - 2017-10-02 13:30 +0200
      Re: [PATCH 0/2 v8] oom: capture unreclaimable slab info in oom  message "Yang Shi" <yang.s@alibaba-inc.com> - 2017-10-02 22:50 +0200

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