linux-kernel - Re: [PATCH 1/2] break out page allocation warning code

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Message-Id: <20110420093900.45F6.A69D9226@jp.fujitsu.com>
Date:	Wed, 20 Apr 2011 09:39:00 +0900 (JST)
From:	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>
To:	David Rientjes <rientjes@...gle.com>
Cc:	kosaki.motohiro@...fujitsu.com,
	Dave Hansen <dave@...ux.vnet.ibm.com>, linux-mm@...ck.org,
	linux-kernel@...r.kernel.org, Johannes Weiner <hannes@...xchg.org>,
	Michal Nazarewicz <mina86@...a86.com>,
	Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [PATCH 1/2] break out page allocation warning code

> On Tue, 19 Apr 2011, KOSAKI Motohiro wrote:
> 
> > The rule is,
> > 
> > 1) writing comm
> > 	need task_lock
> > 2) read _another_ thread's comm
> > 	need task_lock
> > 3) read own comm
> > 	no need task_lock
> > 
> 
> That was true a while ago, but you now need to protect every thread's 
> ->comm with get_task_comm() or ensuring task_lock() is held to protect 
> against /proc/pid/comm which can change other thread's ->comm.  That was 
> different before when prctl(PR_SET_NAME) would only operate on current, so 
> no lock was needed when reading current->comm.

Right. /proc/pid/comm is evil. We have to fix it. otherwise we need change
all of current->comm user. It's very lots!



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