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 23:24:18 +0200
From:	"Rafael J. Wysocki" <rjw@...k.pl>
To:	Alan Stern <stern@...land.harvard.edu>
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 Thursday, September 16, 2010, Alan Stern wrote:
> 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.  :-)

I know that, but resume actually doesn't need to care about async_error.

Thanks,
Rafael
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