linux-kernel - Re: [PATCH] mm, oom: Fix race when selecting process to kill

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Message-ID: <20131106030000.GA1934@hp530>
Date:	Wed, 6 Nov 2013 04:00:04 +0100
From:	Vladimir Murzin <murzin.v@...il.com>
To:	David Rientjes <rientjes@...gle.com>
Cc:	Luigi Semenzato <semenzato@...gle.com>,
	Sameer Nanda <snanda@...omium.org>,
	Andrew Morton <akpm@...ux-foundation.org>, mhocko@...e.cz,
	Johannes Weiner <hannes@...xchg.org>, rusty@...tcorp.com.au,
	linux-mm@...ck.org, linux-kernel@...r.kernel.org, oleg@...hat.com,
	dserrg@...il.com
Subject: Re: [PATCH] mm, oom: Fix race when selecting process to kill

Ccing Oleg and Sergey

On Tue, Nov 05, 2013 at 05:27:29PM -0800, David Rientjes wrote:
> On Tue, 5 Nov 2013, Luigi Semenzato wrote:
> 
> > It's not enough to hold a reference to the task struct, because it can
> > still be taken out of the circular list of threads.  The RCU
> > assumptions don't hold in that case.
> > 
> 
> Could you please post a proper bug report that isolates this at the cause?
>
Hi David!

I think it has already been reported[1] and actively discussed. Oleg has
confirmed that while_each_thread() is not safe under rcu_read_lock()[2].

Oleg, any news about your activity for fixing that?

[1] http://www.spinics.net/lists/linux-mm/msg54836.html
[2] http://marc.info/?l=linux-kernel&m=127688978121665
> Thanks.
> 
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