linux-kernel - Re: [PATCH/RFC] asm-generic/mutex-dec.h: add SMP support

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Message-Id: <201105300900.02884.arnd@arndb.de>
Date:	Mon, 30 May 2011 09:00:02 +0200
From:	Arnd Bergmann <arnd@...db.de>
To:	Mike Frysinger <vapier@...too.org>
Cc:	linux-kernel@...r.kernel.org,
	Andrew Morton <akpm@...ux-foundation.org>,
	linux-arch@...r.kernel.org, uclinux-dist-devel@...ckfin.uclinux.org
Subject: Re: [PATCH/RFC] asm-generic/mutex-dec.h: add SMP support

On Monday 30 May 2011 05:19:28 Mike Frysinger wrote:
> To make these guys work on SMP systems, we just need to sprinkle a few
> barriers around.
> 
> Signed-off-by: Mike Frysinger <vapier@...too.org>
> ---
> note: this is what the Blackfin SMP port is using, but it doesn't seem
> like other SMP ports are ... so I wonder if we're just trying too hard
> and these barriers aren't actually necessary ?

On some architectures, atomic instructions are implicit barriers. On
others, the cmpxchg() macro contains a barrier. I'm not sure if there
is other code relying on that.

	Arnd
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