linux-kernel - Re: [PATCH 1/3 for 2.6.38] oom: oom_kill_process: don't set TIF

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Message-ID: <AANLkTi=YnG7tYCSrCPTNSQANOkD2MkP0tMjbOyZbx4NG@mail.gmail.com>
Date:	Mon, 14 Mar 2011 12:35:52 -0700
From:	Linus Torvalds <torvalds@...ux-foundation.org>
To:	Oleg Nesterov <oleg@...hat.com>
Cc:	Hugh Dickins <hughd@...gle.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>,
	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>,
	Andrey Vagin <avagin@...nvz.org>,
	David Rientjes <rientjes@...gle.com>,
	Frantisek Hrbata <fhrbata@...hat.com>, linux-mm@...ck.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/3 for 2.6.38] oom: oom_kill_process: don't set
 TIF_MEMDIE if !p->mm

On Mon, Mar 14, 2011 at 12:04 PM, Oleg Nesterov <oleg@...hat.com> wrote:
> oom_kill_process() simply sets TIF_MEMDIE and returns if PF_EXITING.
> This is very wrong by many reasons. In particular, this thread can
> be the dead group leader. Check p->mm != NULL.

Explain more, please. Maybe I'm missing some context because I wasn't
cc'd on the original thread, but PF_EXITING gets set by exit_signal(),
and exit_mm() is called almost immediately afterwards which will set
p->mm to NULL.

So afaik, this will basically just remove the whole point of the code
entirely - so why not remove it then?

The combination of testing PF_EXITING and p->mm just doesn't seem to
make any sense.

                      Linus
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