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Date: Tue, 04 Dec 2007 20:02:47 +0100
From: Jarek Poplawski <jarkao2@gmail.com>
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To: Alan Stern <stern@rowland.harvard.edu>
CC: Jarek Poplawski <jarkao2@o2.pl>, Ingo Molnar <mingo@elte.hu>,
       Linux-pm mailing list <linux-pm@lists.linux-foundation.org>,
       Kernel development list <linux-kernel@vger.kernel.org>,
       Peter Zijlstra <peterz@infradead.org>
Subject: Re: Need lockdep help
References: <Pine.LNX.4.44L0.0712041000540.4321-100000@iolanthe.rowland.org>
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Alan Stern wrote, On 12/04/2007 04:17 PM:
...

> Furthermore, in this case deadlock isn't really impossible -- it could 
> occur if there were a bug somewhere else in the kernel.  So lockdep was 
> correct to warn that deadlock might occur.


Alan, if the scenario was like you described at the beginning, there was
no deadlock possible, unless some errors in the notifier. These #1-#3
threads were only helpful to guess what lockdep could 'think', but I
guess notifier doesn't use 2 rivaling threads for a wake, so, lockdep
probably needed additional information. And you really can't consider
any hypothetical kernel bugs here because then each lock is vulnerable.

Regards,
Jarek P.