linux-kernel - Re: [PATCH] PM: Fix potential issue with failing asynchronous suspend (was: Re: [PATCH] PM: Prevent waiting ...)

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Date:	Thu, 16 Sep 2010 17:00:12 -0400 (EDT)
From:	Alan Stern <stern@...land.harvard.edu>
To:	"Rafael J. Wysocki" <rjw@...k.pl>
cc:	Colin Cross <ccross@...roid.com>, <linux-kernel@...r.kernel.org>,
	<linux-pm@...ts.linux-foundation.org>, Pavel Machek <pavel@....cz>
Subject: Re: [PATCH] PM: Fix potential issue with failing asynchronous suspend
 (was: Re: [PATCH] PM: Prevent waiting ...)

On Thu, 16 Sep 2010, Rafael J. Wysocki wrote:

> From: Rafael J. Wysocki <rjw@...k.pl>
> Subject: PM: Fix potential issue with failing asynchronous suspend
> 
> There is a potential issue with the asynchronous suspend code that
> a device driver suspending asynchronously may not notice that it
> should back off.  There are two failing scenarions, (1) when the
> driver is waiting for a driver suspending synchronously to complete
> and that second driver returns error code, in which case async_error
> won't be set and the waiting driver will continue suspending and (2)
> after the driver has called device_pm_wait_for_dev() and the waited
> for driver returns error code, in which case the caller of
> device_pm_wait_for_dev() will not know that there was an error and
> will continue suspending.
> 
> To fix this issue make __device_suspend() set async_error, so
> async_suspend() doesn't need to set it any more, and make
> device_pm_wait_for_dev() return async_error, so that its callers
> can check whether or not they should continue suspending.
> 
> No more changes are necessary, since device_pm_wait_for_dev() is
> not used by any drivers' suspend routines at the moment.

You just squeaked by, since it is _is_ being used by a USB _resume_
routine.  :-)

Alan Stern

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