linux-kernel - Re: [PATCH -mm 1/3] mm/oom_kill: remove the wrongfatal_signal

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Date:	Thu, 1 Oct 2015 00:20:57 +0900
From:	Tetsuo Handa <penguin-kernel@...ove.SAKURA.ne.jp>
To:	oleg@...hat.com
Cc:	rientjes@...gle.com, akpm@...ux-foundation.org, kwalker@...hat.com,
	mhocko@...nel.org, skozina@...hat.com, linux-kernel@...r.kernel.org
Subject: Re: [PATCH -mm 1/3] mm/oom_kill: remove the wrongfatal_signal_pending()

Oleg Nesterov wrote:
> > This fatal_signal_pending() check is about to be added by me because the OOM
> > killer spams the kernel log when the mm struct which the OOM victim is using
> > is shared by many threads. ( http://marc.info/?l=linux-mm&m=143256441501204 )
> 
> OK, I see, but it is wrong.
> 
> But I don't really understand "shared by many threads", I mean "threads" is
> confusing word. I guess you mean CLONE_VM processes, otherwise we shouldn't
> see the additional spam.

Right.

> 
> And 1000 CLONE_VM processes + "and the lock dependency prevents all threads
> except the OOM victim thread from terminating until they get TIF_MEMDIE flag"
> look like a really pathological case...

Right. But I saw that
http://lkml.kernel.org/r/201509271451.DEB86404.tMFFHSVQFOLOOJ@I-love.SAKURA.ne.jp
took 3 minites to kill one mm struct because dump_header() was called for many
times.

> > I was waiting for your comment about whether you depend on
> > the "sharing same memory" message with KERN_ERR level.
> > ( http://marc.info/?l=linux-mm&m=144120389203133 )
> >
> > If nobody else objects, I think we can remove the "sharing same memory"
> > message. ( http://marc.info/?l=linux-mm&m=144119325831959 )
> 
> OK, will you agree with v2 which also removes pr_warn?

Yes.
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