Re: [PATCH/RFC] MMC: remove unbalanced pm_runtime_suspend()

Alan Stern
2011-04-20T21:16:14Z

On Wed, 20 Apr 2011, Rafael J. Wysocki wrote:

> On Wednesday, April 20, 2011, Alan Stern wrote:
> > On Wed, 20 Apr 2011, Guennadi Liakhovetski wrote:
> ...
> > Ah, now I see the problem. It looks like we did not give sufficient
> > thought to the case where a device starts off (and therefore should
> > finish up) in a powered-down state. Calling pm_runtime_put_sync()
> > after unbinding the device driver seems a little futile -- with no
> > driver, the subsystem may not be able to power-down the device!
> >
> > Rafael, how do you think we should handle this? Get rid of the
> > pm_runtime_get_no_resume() and pm_runtime_put_sync() calls in
> > dd.c:__device_release_driver()?
>
> I think we need pm_runtime_barrier() in there. Otherwise we risk
> removing the driver while there's a runtime PM request pending.
>
> But we can move the pm_runtime_put_sync() before driver_sysfs_remove().

What happens if another runtime PM request is queued between the
put_sync() and the remove callback? We may need a safe way to prevent
async runtime PM requests while still allowing synchronous requests.

Alan Stern