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From: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
To: David Howells <dhowells@redhat.com>
Cc: kosaki.motohiro@jp.fujitsu.com,
	"Paul E. McKenney" <paulmck@linux.vnet.ibm.com>,
	LKML <linux-kernel@vger.kernel.org>,
	linux-mm <linux-mm@kvack.org>,
	Andrew Morton <akpm@linux-foundation.org>,
	David Rientjes <rientjes@google.com>,
	KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Subject: Re: oom: __task_cred() need rcu_read_lock()
Date: Fri, 20 Aug 2010 09:08:52 +0900 (JST)	[thread overview]
Message-ID: <20100820084820.5FDB.A69D9226@jp.fujitsu.com> (raw)
In-Reply-To: <7682.1282230394@redhat.com>

Hi

> KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com> wrote:
> 
> > dump_tasks() can call __task_cred() safely because we are holding
> > tasklist_lock. but rcu lock validator don't have enough knowledge and
> > it makes following annoying warning.
> 
> No, it can't.  The tasklist_lock is not protection against the creds changing
> on another CPU.

Thank you for correction.

I suppose you mean I missed CONFIG_TREE_PREEMPT_RCU, right?
As far as my grepping, other rcu implementation and spinlock use 
preempt_disable(). In other word, Can I assume usual distro user 
don't hit this issue?

Thanks.



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  reply	other threads:[~2010-08-20  0:08 UTC|newest]

Thread overview: 4+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2010-08-19 13:06 KOSAKI Motohiro
2010-08-19 15:06 ` David Howells
2010-08-20  0:08   ` KOSAKI Motohiro [this message]
2010-08-20  8:50   ` David Howells

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