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Date: Wed, 7 Oct 2015 15:00:36 +0200
From: Peter Zijlstra <peterz@infradead.org>
To: "H. Peter Anvin" <hpa@zytor.com>
Cc: Pranith Kumar <bobby.prani@gmail.com>,
        Thomas Gleixner <tglx@linutronix.de>, Ingo Molnar <mingo@redhat.com>,
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Subject: Re: [PATCH] x86: cmpxchg_double: Add missing memory clobber
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On Tue, Oct 06, 2015 at 02:39:02PM -0700, H. Peter Anvin wrote:

> However, I think one of the major uses for cmpxchg_double() is for page
> table manipulation, and for that it isn't clear that a compiler barrier
> is needed nor desired.

See mm/slub.c, that uses cmpxchg_double() (the LOCK prefixed one) and
one would expect that to also include a compiler barrier.