linux-kernel - Re: [PATCH] bitops: Use volatile in generic atomic bitops.

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Message-Id: <201107271455.39511.arnd@arndb.de>
Date:	Wed, 27 Jul 2011 14:55:39 +0200
From:	Arnd Bergmann <arnd@...db.de>
To:	Will Newton <will.newton@...il.com>
Cc:	Linux Kernel list <linux-kernel@...r.kernel.org>, stable@...nel.org
Subject: Re: [PATCH] bitops: Use volatile in generic atomic bitops.

On Wednesday 27 July 2011, Will Newton wrote:
> The generic atomic bitops currently explicitly cast away the
> volatile from the pointer passed to them. This will allow the
> access to the bitfield to happen outside of the critical section
> thus making the bitops no longer interrupt-safe. Remove this cast
> and add a volatile keyword to make sure all accesses to the
> bitfield happen inside the critical section.
> 
> Signed-off-by: Will Newton <will.newton@...tec.com>

Have you observed this behavior? The interrupt disable/enable should
always come with a barrier that should prevent the bitops from
leaking out, so I don't see how this causes problems in practice.

	Arnd
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