On Sat, 8 Aug 2009, Rafael J. Wysocki wrote: > > The problem with this is that it calls pm_runtime_disable() at a time > > when the driver is still supposed to be in control of the device. > > Interfering with the driver's legitimate activity in this way is a bad > > thing to do. > > > > The difficulty here is that our requirements are a little > > contradictory. We want to prevent all runtime PM callbacks while the > > remove method is running, but we also want the remove method to be able > > to carry out its own runtime PM activities. > > > > So maybe what we really need is more like a barrier. That is, > > something that will do a "get", wait for outstanding callbacks to > > finish, carry out a resume if one is pending, and cancel other pending > > requests. This could easily share code with pm_runtime_disable. We > > should be able to use this for both probe and remove. > > Isn't it what's done in rev. 14? > > pm_runtime_disable(dev); > pm_runtime_get_noresume(dev); > pm_runtime_enable(dev); > > is exactly a barrier like this. It's not exactly the same because it disables runtime PM for a short time. A barrier never disables runtime PM. > How exactly would you like to implement it > instead? As described above. The barrier would be equivalent to pm_runtime_get_noresume followed by pm_runtime_disable except that it wouldn't actually disable anything. > > Perhaps this means we don't want to disable runtime PM during system > > sleep callbacks, but instead use the "barrier" scheme. > > I'm not really sure about that. I'd rather do what's right now in the patch > (well, that's why it's in there) until drivers and bus types start using the > runtime PM framework. If it turns out to be problematic, we'll change it > later. All right. Since it involves a race, the problem may not show up for a while. Alan Stern _______________________________________________ linux-pm mailing list linux-pm@xxxxxxxxxxxxxxxxxxxxxxxxxx https://lists.linux-foundation.org/mailman/listinfo/linux-pm
