linux-kernel - Re: [ 42/78] PM / Runtime: dont forget to wake up waitqueue on failure

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Date:	Sat, 14 Apr 2012 06:23:23 +0100
From:	Ben Hutchings <ben@...adent.org.uk>
To:	Greg KH <gregkh@...uxfoundation.org>,
	Alan Stern <stern@...land.harvard.edu>
Cc:	linux-kernel@...r.kernel.org, stable@...r.kernel.org,
	torvalds@...ux-foundation.org, akpm@...ux-foundation.org,
	alan@...rguk.ukuu.org.uk, "Rafael J. Wysocki" <rjw@...k.pl>
Subject: Re: [ 42/78] PM / Runtime: dont forget to wake up waitqueue on
 failure

On Wed, 2012-04-11 at 16:11 -0700, Greg KH wrote:
> 3.3-stable review patch.  If anyone has any objections, please let me know.
> 
> ------------------
> 
> From: Alan Stern <stern@...land.harvard.edu>
> 
> commit f2791d733a2f06997b573d1a3cfde21e6f529826 upstream.
> 
> This patch (as1535) fixes a bug in the runtime PM core.  When a
> runtime suspend attempt completes, whether successfully or not, the
> device's power.wait_queue is supposed to be signalled.  But this
> doesn't happen in the failure pathway of rpm_suspend() when another
> autosuspend attempt is rescheduled.  As a result, a task can get stuck
> indefinitely on the wait queue (I have seen this happen in testing).
> 
> The patch fixes the problem by moving the wake_up_all() call up near
> the start of the failure code.
[...]

It looks like this is also relevant to 3.2, but the code got moved
around a bit between 3.2 and 3.3.  Attaching my (untested) backport.

Ben.

-- 
Ben Hutchings
It is easier to change the specification to fit the program than vice versa.

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