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

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Message-Id: <201509301042.DEE34882.OFHSMLQtOOVFFJ@I-love.SAKURA.ne.jp>
Date:	Wed, 30 Sep 2015 10:42:26 +0900
From:	Tetsuo Handa <penguin-kernel@...ove.SAKURA.ne.jp>
To:	rientjes@...gle.com, oleg@...hat.com
Cc:	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 wrong fatal_signal_pending()

David Rientjes wrote:
> On Tue, 29 Sep 2015, Oleg Nesterov wrote:
> 
> > The fatal_signal_pending() was added to suppress unnecessary "sharing
> > same memory" message, but it can't 100% help anyway because it can be
> > false-negative; SIGKILL can be already dequeued.
> > 
> > And worse, it can be false-positive due to exec or coredump. exec is
> > mostly fine, but coredump is not. It is possible that the group leader
> > has the pending SIGKILL because its sub-thread originated the coredump,
> > in this case we must not skip this process.
> > 
> > We could probably add the additional ->group_exit_task check but this
> > pach just removes fatal_signal_pending(), the extra "Kill process" is
> > unlikely and doesn't really hurt.

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 )

> > 
> > Signed-off-by: Oleg Nesterov <oleg@...hat.com>
> 
> Acked-by: David Rientjes <rientjes@...gle.com>
> 
> In addition, I'm really debating whether we need the "sharing same memory" 
> line or not.  In the past, it has been helpful because there is no other 
> way to determine what the kernel has killed other than to leave an 
> artifact behind in the kernel log.  I can imagine that this could easily 
> spam the kernel log, though, accompanied by oom killer messages that are 
> already very verbose.  I wouldn't mind if it the printk were removed 
> entirely.
> 

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 )
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