linux-kernel - Re: [patch] mm, oom: remove task

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Message-ID: <20150924194528.GB3009@cmpxchg.org>
Date:	Thu, 24 Sep 2015 15:45:28 -0400
From:	Johannes Weiner <hannes@...xchg.org>
To:	David Rientjes <rientjes@...gle.com>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	Oleg Nesterov <oleg@...hat.com>,
	Michal Hocko <mhocko@...nel.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Kyle Walker <kwalker@...hat.com>,
	Christoph Lameter <cl@...ux.com>,
	Vladimir Davydov <vdavydov@...allels.com>,
	linux-mm <linux-mm@...ck.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Stanislav Kozina <skozina@...hat.com>,
	Tetsuo Handa <penguin-kernel@...ove.sakura.ne.jp>
Subject: Re: [patch] mm, oom: remove task_lock protecting comm printing

On Tue, Sep 22, 2015 at 04:30:13PM -0700, David Rientjes wrote:
> The oom killer takes task_lock() in a couple of places solely to protect
> printing the task's comm.
> 
> A process's comm, including current's comm, may change due to
> /proc/pid/comm or PR_SET_NAME.
> 
> The comm will always be NULL-terminated, so the worst race scenario would
> only be during update.  We can tolerate a comm being printed that is in
> the middle of an update to avoid taking the lock.
> 
> Other locations in the kernel have already dropped task_lock() when
> printing comm, so this is consistent.
> 
> Suggested-by: Oleg Nesterov <oleg@...hat.com>
> Signed-off-by: David Rientjes <rientjes@...gle.com>

Acked-by: Johannes Weiner <hannes@...xchg.org>
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