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From: Arnd Bergmann <arnd@arndb.de>
To: Will Newton <will.newton@gmail.com>
Cc: Linux Kernel list <linux-kernel@vger.kernel.org>, stable@kernel.org
Subject: Re: [PATCH] bitops: Use volatile in generic atomic bitops.
Date: Wed, 27 Jul 2011 14:55:39 +0200	[thread overview]
Message-ID: <201107271455.39511.arnd@arndb.de> (raw)
In-Reply-To: <CAFbHwiQaYeQSwRykhKp57rQ8xLKSst9MXF7YJoQjEm0V+WN4Qw@mail.gmail.com>

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@imgtec.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

  reply	other threads:[~2011-07-27 12:55 UTC|newest]

Thread overview: 8+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2011-07-27 12:21 [PATCH] bitops: Use volatile in generic atomic bitops Will Newton
2011-07-27 12:55 ` Arnd Bergmann [this message]
2011-07-27 13:09   ` Will Newton
2011-07-27 14:28     ` Arnd Bergmann
2011-07-27 14:32       ` Will Newton
2011-07-27 15:22         ` Arnd Bergmann
2011-07-27 15:59           ` Will Newton
2011-07-27 16:15 ` [stable] " Greg KH

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