On Wednesday 10 June 2009, Oliver Neukum wrote: > Am Mittwoch, 10. Juni 2009 21:27:56 schrieb Rafael J. Wysocki: > > > What happens if the parent's parent is also suspended? It seems to me > > > that you must code this recursively. > > > > Hmm, I thought I did. > > > > [Looks] > > > > pm_request_resume(dev) will call pm_request_resume(dev->parent), if > > necessary, and that will call pm_request_resume(dev->parent->parent) and so > > on. Each of them will queue a work item and the one for the topmost parent > > will be queued first. So, the resume requests for all parents will be > > executed before the one for the device, due to the fact that the workqueue > > is singlethread. > > Sneaky, I overlooked that. > > > Well, there is a bug related to it, namely pm_autosuspend() may change the > > status to RPM_SUSPENDED after pm_request_resume() has changed it to > > RPM_WAKE, that needs fixing. > > Ok, maybe this is related. You recurse if the parent isn't in RPM_ACTIVE. > But that is not enough. You must ensure that all the nodes higher up stay > in RPM_ACTIVE. It seems to me that you must go up until you find an > active node (or the root) and put it a blocked state. If you're referring to pm_autoresume(), then this again is tricky. We have queued up resume requests for the device's parent, its parent etc., the topmost one goes first. The workqueue is singlethread, so pm_autoresume() is going to be run for all parents before the device itself, so if that were the only resume mechanism, it would be enough to check if the parent is RPM_ACTIVE. *However*, there also is pm_resume_sync(), which can take the device directly from RPM_SUSPENDED to RPM_RESUMING and that may be done in parallel with our pm_autoresume(). That's why I put the wait_for_completion() in there. Best, Rafael _______________________________________________ linux-pm mailing list linux-pm@xxxxxxxxxxxxxxxxxxxxxxxxxx https://lists.linux-foundation.org/mailman/listinfo/linux-pm
