Re: [PATCH] x86: cmpxchg_double: Add missing memory clobber

From	Peter Zijlstra <peterz@infradead.org>
Newsgroups	linux.kernel
Subject	Re: [PATCH] x86: cmpxchg_double: Add missing memory clobber
Date	2015-10-07 15:10 +0200
Message-ID	<qgWDL-5In-1@gated-at.bofh.it> (permalink)
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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.
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[PATCH] x86: cmpxchg_double: Add missing memory clobber Pranith Kumar <bobby.prani@gmail.com> - 2015-10-06 21:00 +0200
  Re: [PATCH] x86: cmpxchg_double: Add missing memory clobber "H. Peter Anvin" <hpa@zytor.com> - 2015-10-06 22:20 +0200
    Re: [PATCH] x86: cmpxchg_double: Add missing memory clobber Pranith Kumar <bobby.prani@gmail.com> - 2015-10-06 22:30 +0200
      Re: [PATCH] x86: cmpxchg_double: Add missing memory clobber "H. Peter Anvin" <hpa@zytor.com> - 2015-10-06 23:40 +0200
        Re: [PATCH] x86: cmpxchg_double: Add missing memory clobber Peter Zijlstra <peterz@infradead.org> - 2015-10-07 15:10 +0200

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