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Message-ID: <17309.366.751356.538376@cargo.ozlabs.ibm.com>
Date: Mon, 12 Dec 2005 15:49:50 +1100
From: Paul Mackerras <paulus@samba.org>
To: Andrew Morton <akpm@osdl.org>
Cc: paulmck@us.ibm.com, oleg@tv-sign.ru, vatsa@in.ibm.com,
       linux-kernel@vger.kernel.org, dipankar@in.ibm.com
Subject: Re: [PATCH] Fix RCU race in access of nohz_cpu_mask
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Andrew Morton writes:

> So foo_mb() in preemptible code is potentially buggy.
> 
> I guess we assume that a context switch accidentally did enough of the
> right types of barriers for things to work OK.

The context switch code on powerpc includes an mb() for exactly this
reason.

Paul.
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