linux-kernel - Re: [PATCH 09/12] oom: remove PF

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Message-ID: <alpine.DEB.2.00.1006022332320.22441@chino.kir.corp.google.com>
Date:	Wed, 2 Jun 2010 23:34:52 -0700 (PDT)
From:	David Rientjes <rientjes@...gle.com>
To:	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>
cc:	"Luis Claudio R. Goncalves" <lclaudio@...g.org>,
	LKML <linux-kernel@...r.kernel.org>,
	linux-mm <linux-mm@...ck.org>, Oleg Nesterov <oleg@...hat.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>,
	Nick Piggin <npiggin@...e.de>
Subject: Re: [PATCH 09/12] oom: remove PF_EXITING check completely

On Thu, 3 Jun 2010, KOSAKI Motohiro wrote:

> Currently, PF_EXITING check is completely broken. because 1) It only
> care main-thread and ignore sub-threads

Then check the subthreads.

> 2) If user enable core-dump
> feature, it can makes deadlock because the task during coredump ignore
> SIGKILL.
> 

It may ignore SIGKILL, but does not ignore fatal_signal_pending() being 
true which gives it access to memory reserves with my patchset so that it 
may quickly finish.

> The deadlock is certenaly worst result, then, minor PF_EXITING
> optimization worth is relatively ignorable.
> 
> This patch removes it.
> 
> Signed-off-by: KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>
> Acked-by: Oleg Nesterov <oleg@...hat.com>

Nacked-by: David Rientjes <rientjes@...gle.com>

You have no real world experience in using the oom killer for memory 
containment and don't understand how critical it is to protect other 
vital system tasks that are needlessly killed as the result of this patch.
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