linux-kernel - Re: [PATCH] aio: use cmpxchg in aio_read_evt() instead of aio_ring_info->ring

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Message-ID: <48692008.3010003@oracle.com>
Date:	Mon, 30 Jun 2008 11:03:52 -0700
From:	Zach Brown <zach.brown@...cle.com>
To:	Nikanth Karthikesan <knikanth@...e.de>
CC:	linux-aio@...ck.org, linux-kernel@...r.kernel.org,
	Benjamin LaHaise <bcrl@...ck.org>,
	Jeff Moyer <jmoyer@...hat.com>
Subject: Re: [PATCH] aio: use cmpxchg in aio_read_evt() instead of aio_ring_info->ring_lock

Nikanth Karthikesan wrote:
> Use cmpxchg in aio_read_evt() and remove the aio_ring_info->ring_lock

I don't think this is safe because the cmpxhg() can't differentiate the
0 it read at one point with a 0 that it reads in the future after other
racing threads have done enough work on the ring index to wrap it.

- z
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