From: Manfred Spraul <manfred@colorfullife.com>
To: Jack Steiner <steiner@sgi.com>
Cc: Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH] - Fix memory ordering problem in wake_futex()
Date: Sun, 25 Dec 2005 17:02:33 +0100 [thread overview]
Message-ID: <43AEC299.1010707@colorfullife.com> (raw)
In-Reply-To: <20051224034504.GC24614@sgi.com>
Again replying to myself, sorry:
Jack Steiner wrote:
>On Fri, Dec 23, 2005 at 11:23:11PM +0100, Manfred Spraul wrote:
>
>
>>Bad race.
>>Unfortuantely the scenario that you describe is quite frequent:
>>- autoremove_wake_function()
>>
>>
Not a bug, but for very subtile reasons:
There are no writes to the wait_queue structure except the
list_del_init(), and for list_del_init() no memory barriers are required
because finish_wait() uses list_empty_careful(), i.e. the spin_lock() is
only bypassed if both write operations from list_del_init() have completed.
>>- ipc/sem.c (search for IN_WAKEUP)
>>
>>
fixed in -rc7.
--
Manfred
next prev parent reply other threads:[~2005-12-25 16:02 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2005-12-23 22:23 [PATCH] - Fix memory ordering problem in wake_futex() Manfred Spraul
2005-12-23 22:52 ` Manfred Spraul
2005-12-24 3:45 ` Jack Steiner
2005-12-25 16:02 ` Manfred Spraul [this message]
-- strict thread matches above, loose matches on Subject: below --
2005-12-23 16:38 Jack Steiner
2005-12-23 17:05 ` Joe Seigh
2005-12-23 20:48 ` Olof Johansson
2005-12-23 21:32 ` Jack Steiner
2005-12-23 21:59 ` Olof Johansson
2005-12-23 23:48 ` Robin Holt
2005-12-24 13:45 ` Jack Steiner
2005-12-24 18:13 ` Olof Johansson
2005-12-27 16:30 ` Jack Steiner
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