On Sunday, November 07, 2010, Alan Stern wrote: > On Wed, 3 Nov 2010, Rafael J. Wysocki wrote: > > > On Tuesday, November 02, 2010, Raj Kumar wrote: > > > > > > Hi, > > > > > > There is a one issue coming regarding the run time power management during system suspend, Suppose > > > system suspend is going on and before the suspend callback of driver is executed, driver issues a runtime resume to run time power management core before it gets > > > the system suspend call back but System suspend is going on then how the run time power management prevents this condition? > > > > > > As I saw the code during dpm_prepare, power usage count is incremented by 1 by calling pm_runtime_get_noresume(dev) and then it calls > > > pm_runtime_barrier, > > > > > > Since During System suspend, driver calls pm_runtime_get which will invoke > > > > > > atomic_inc(&dev->power.usage_count); > > > > > > which increments the power usage count and calls pm_request_resume which does not have any check on power usage count, > > > > pm_request_resume() called during system suspend will not have any effect, unless it is called before > > the pm_runtime_barrier() in dpm_prepare(), in which case the device is going to be resumed and > > system suspend will be aborted, because the PM workqueue if frozen before the suspend of > > devices. I should have said that it only affects the devices for which device_may_wakeup() returns 'true'. > Should pm_request_resume be changed? Maybe it should abort a system > sleep transition. Or maybe it should abort the sleep if the device in > question has already been suspended. Well, I don't think so, at least not always. Perhaps it's better to let the caller execute pm_wakeup_event() or pm_stay_awake() before calling pm_request_resume() in case it wants to abort system suspend in progress. I guess the core might do that as well, actually, in the situation described above ... Thanks, Rafael _______________________________________________ linux-pm mailing list linux-pm@xxxxxxxxxxxxxxxxxxxxxxxxxx https://lists.linux-foundation.org/mailman/listinfo/linux-pm
