On Thu, 24 Jun 2010, Rafael J. Wysocki wrote: > > 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. Yeah, okay, but who's going to do that? > > I'm not sure which model is better in practice. No doubt the Android people > > will prefer their way. > > I suppose so. It may not make a significant difference in the end. You can always emulate the wakelock approach by not calling pm_stay_awake() when you know there is an earlier call still pending. > > 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? Yes. The unfreezable workqueue threads don't have to worry about getting frozen while their queues are non-empty. :-) > I'm not sure if that helps a lot, because > new work items may still be added after the workqueue thread has been frozen. That's not the point. If a wakeup handler queues a work item (for example, by calling pm_request_resume) then it wouldn't need to guess a timeout. The work item would be guaranteed to run before the system could suspend again. > > 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? I suppose so. It would make the GFP_ATOMIC allocations a little more reliable. Alan Stern _______________________________________________ linux-pm mailing list linux-pm@xxxxxxxxxxxxxxxxxxxxxxxxxx https://lists.linux-foundation.org/mailman/listinfo/linux-pm
