linux-kernel - oom-killer is crazy? (Was: [PATCH 0/3] uprobes fixes for 3.5)

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Message-ID: <20120608140328.GA26650@redhat.com>
Date:	Fri, 8 Jun 2012 16:03:28 +0200
From:	Oleg Nesterov <oleg@...hat.com>
To:	Hugh Dickins <hughd@...gle.com>, Ingo Molnar <mingo@...e.hu>,
	Peter Zijlstra <peterz@...radead.org>,
	Srikar Dronamraju <srikar@...ux.vnet.ibm.com>,
	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>,
	Dave Jones <davej@...hat.com>,
	David Rientjes <rientjes@...gle.com>
Cc:	Ananth N Mavinakayanahalli <ananth@...ibm.com>,
	Anton Arapov <anton@...hat.com>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>,
	linux-kernel@...r.kernel.org
Subject: oom-killer is crazy? (Was: [PATCH 0/3] uprobes fixes for 3.5)

On 06/07, Oleg Nesterov wrote:
>
> This doesn't depend on other uprobes patches I sent, and I think
> this is 3.5 material.

And during the testing I found another thing which should be fixed
in 3.5 imho. I noticed that oom-killer goes crazy. In the simplest
case, when there is the single and "obvious" memory hog it kills
sshd daemon.

Hmm. oom_badness() does

	if (has_capability_noaudit(p, CAP_SYS_ADMIN))
		points -= 30 * totalpages / 1000;

very nice, but what if this underflows? points is unsigned long.
points += p->signal->oom_score_adj... looks suspicious too.

Looks like we should remove "unsigned" from oom_badness() and
its callers? Probably not, it does "return points ? points : 1".

Confused.

Oleg.

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