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

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Message-ID: <alpine.DEB.2.10.1509291534170.3375@chino.kir.corp.google.com>
Date:	Tue, 29 Sep 2015 15:36:12 -0700 (PDT)
From:	David Rientjes <rientjes@...gle.com>
To:	Oleg Nesterov <oleg@...hat.com>
cc:	Andrew Morton <akpm@...ux-foundation.org>,
	Kyle Walker <kwalker@...hat.com>,
	Michal Hocko <mhocko@...nel.org>,
	Stanislav Kozina <skozina@...hat.com>,
	Tetsuo Handa <penguin-kernel@...ove.sakura.ne.jp>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH -mm 1/3] mm/oom_kill: remove the wrong
 fatal_signal_pending()

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.
> 
> 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.
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