On Thursday, April 21, 2011, Alan Stern wrote: > On Thu, 21 Apr 2011, Rafael J. Wysocki wrote: > > > > > If we choose this approach, then yes, we should provide a suitable API, but > > > > I'm still thinking it would be simpler to move the pm_runtime_put_sync() before driver_sysfs_remove() and make the rule as I said previously. :-) > > > > > > The problem is synchronization. At what point is the driver supposed > > > to stop queuing runtime PM requests? It would have to be sometime > > > before the pm_runtime_barrier() call. How is the driver supposed to > > > know when that point is reached? The remove routine isn't called until > > > later. > > > > Executing the driver's callback is not an ideal solution either, because > > it simply may be insufficient (it may be necessary to execute the power > > domain and/or subsystem callbacks, pretty much what rpm_suspend() does, > > but without taking the usage counter into consideration). > > That's why I suggested a new API. It could do the right callbacks. > > > Moreover, if we want the driver's ->remove() to do the cleanup anyway, > > there's not much point in doing any cleanup before in the core. Also, > > there's a little problem that the bus ->remove() is called before the > > driver's ->remove(), so it may not be entirely possible to power down > > the device when the driver's ->remove() is called already. > > Actually, the bus->remove() callback (if there is one) is responsible > for invoking the driver's callback. Ah, sorry, I misread the code in __device_release_driver() (too little coffee perhaps). > The subsystem should be smart enough to handle runtime PM requests while > the driver's remove callback is running. If we make such a rule, we may as well remove all of the runtime PM calls from __device_release_driver(). > > I think the current code is better than any of the alternatives considered > > so far. > > Then you think Guennadi should leave his patch as it is, including the > "reversed" put/get? This, or we need to remove the runtime PM calls from __device_release_driver(). I'm a bit worried about the driver_sysfs_remove() and the bus notifier that in theory may affect the runtime PM callbacks potentially executed before ->remove() is called. Rafael -- To unsubscribe from this list: send the line "unsubscribe linux-mmc" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
