linux-kernel - Re: [PATCH 1/2 v3] wait: add wait_event_lock

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Date:	Fri, 30 Nov 2012 02:48:42 -0800
From:	Andrew Morton <akpm@...ux-foundation.org>
To:	Lukas Czerner <lczerner@...hat.com>
Cc:	linux-kernel@...r.kernel.org, linux-raid@...r.kernel.org,
	axboe@...nel.dk, jmoyer@...hat.com, Neil Brown <neilb@...e.de>,
	David Howells <dhowells@...hat.com>,
	Ingo Molnar <mingo@...e.hu>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>
Subject: Re: [PATCH 1/2 v3] wait: add wait_event_lock_irq() interface

On Fri, 30 Nov 2012 11:42:40 +0100 Lukas Czerner <lczerner@...hat.com> wrote:

> New wait_event{_interruptible}_lock_irq{_cmd} macros added. This commit
> moves the private wait_event_lock_irq() macro from MD to regular wait
> includes, introduces new macro wait_event_lock_irq_cmd() instead of using
> the old method with omitting cmd parameter which is ugly and makes a use
> of new macros in the MD. It also introduces the _interruptible_ variant.
> 
> The use of new interface is when one have a special lock to protect data
> structures used in the condition, or one also needs to invoke "cmd"
> before putting it to sleep.
> 
> All new macros are expected to be called with the lock taken. The lock
> is released before sleep and is reacquired afterwards. We will leave the
> macro with the lock held.
> 
> Note to DM: IMO this should also fix theoretical race on waitqueue while
> using simultaneously wait_event_lock_irq() and wait_event() because of
> lack of locking around current state setting and wait queue removal.

Does this fix the sparse warning which Fengguang just sent us?
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