linux-kernel - Re: [PATCH] i386 add idle notifier

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Message-ID: <20061129231535.GE15186@flint.arm.linux.org.uk>
Date:	Wed, 29 Nov 2006 23:15:35 +0000
From:	Russell King <rmk+lkml@....linux.org.uk>
To:	Andrew Morton <akpm@...l.org>
Cc:	eranian@....hp.com, Christoph Hellwig <hch@...radead.org>,
	linux-kernel@...r.kernel.org, ak@...e.de
Subject: Re: [PATCH] i386 add idle notifier

On Wed, Nov 29, 2006 at 03:05:44PM -0800, Andrew Morton wrote:
> btw, I don't think anyone promised that __test_and_set_bit is atomic wrt
> interrupts on all architectures.  Is OK for x86.

Correct.  The generic version found in include/asm-generic/bitops/non-atomic.h
is not interrupt safe:

/**
 * __test_and_set_bit - Set a bit and return its old value
 * @nr: Bit to set
 * @addr: Address to count from
 *
 * This operation is non-atomic and can be reordered.
 * If two examples of this operation race, one can appear to succeed
 * but actually fail.  You must protect multiple accesses with a lock.
 */

-- 
Russell King
 Linux kernel    2.6 ARM Linux   - http://www.arm.linux.org.uk/
 maintainer of:
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