On Thursday, June 24, 2010, Alan Stern wrote: > On Thu, 24 Jun 2010, Rafael J. Wysocki wrote: > > > > > And what happens if the device gets a second wakeup event before the timer > > > > for the first one expires? > > > > > > Good question. I don't have an answer to it at the moment, but it seems to > > > arise from using a single timer for all events. > > > > > > It looks like it's simpler to make pm_wakeup_event() allocate a timer for each > > > event and make the timer function remove it. That would cause suspend to > > > be blocked until the timer expires without a way to cancel it earlier, though. > > > > So, I decided to try this after all. > > > > Below is a new version of the patch. It introduces pm_stay_awake(dev) and > > pm_relax() that play the roles of the "old" pm_wakeup_begin() and > > pm_wakeup_end(). > > > > pm_wakeup_event() now takes an extra timeout argument and uses it for > > deferred execution of pm_relax(). So, one can either use the > > pm_stay_awake(dev) / pm_relax() pair, or use pm_wakeup_event(dev, timeout) > > if the ending is under someone else's control. > > > > In addition to that, pm_get_wakeup_count() blocks until events_in_progress is > > zero. > > > > Please tell me what you think. > > This is slightly different from the wakelock design. Each call to > pm_stay_awake() must be paired with a call to pm_relax(), allowing one > device to have multiple concurrent critical sections, whereas calls to > pm_wakeup_event() must not be paired with anything. With wakelocks, > you couldn't have multiple pending events for the same device. You could, but you needed to define multiple wakelocks for the same device for this purpose. > I'm not sure which model is better in practice. No doubt the Android people > will prefer their way. I suppose so. > This requires you to define an explicit PCI_WAKEUP_COOLDOWN delay. I > think that's okay; I had to do something similar with USB and SCSI. > (And I still think it would be a good idea to prevent workqueue threads > from freezing until their queues are empty.) I guess you mean the freezable ones? I'm not sure if that helps a lot, because new work items may still be added after the workqueue thread has been frozen. > Instead of allocating the work structures dynamically, would you be > better off using a memory pool? Well, it would be kind of equivalent to defining my own slab cache for that, wouldn't it? Rafael _______________________________________________ linux-pm mailing list linux-pm@xxxxxxxxxxxxxxxxxxxxxxxxxx https://lists.linux-foundation.org/mailman/listinfo/linux-pm
