Re: [linux-pm] subtle pm_runtime_put_sync race and sdio functions

["Rafael J. Wysocki" <rjw@sisk.pl>]

On Sunday, December 26, 2010, Ohad Ben-Cohen wrote:
> On Sun, Dec 26, 2010 at 4:48 AM, Alan Stern <stern@rowland.harvard.edu> wrote:
> > Is there a separate handler responsible for powering the device back
> > on?  What are the names of these handlers?
> 
> wl1271_sdio_power_on() and wl1271_sdio_power_off().
> 
> If you're taking a look, please do so using the latest code as seen on mmc-next:
> 
> git://git.kernel.org/pub/scm/linux/kernel/git/cjb/mmc.git mmc-next
> 
> > That's not a race
> 
> It is.
> 
> If system suspend will continue uninterruptedly, and the driver will
> be suspended (by the SDIO subsystem), then the device will be powered
> down, and everything will work.
> 
> But if something will interrupt the suspend transition _before_ our
> driver is suspended (e.g. some other suspend() handler will fail),
> then we have a problem, because the device will not be reset as the
> driver needs it to be.

Now, that's interesting.  (It still is not a race, though.)
Why does the driver need the device to be reset even though it hasn't
been suspeneded yet?

Rafael