On Thu, 10 Jan 2008, Rafael J. Wysocki wrote: > On Wednesday, 9 of January 2008, Alan Stern wrote: > > On Wed, 9 Jan 2008, Rafael J. Wysocki wrote: > > > > > > In dpm_resume() you shouldn't need to use dpm_list_mtx at all, because > > > > the list_move_tail() comes before the resume_device(). It's the same > > > > as in dpm_power_up(). > > > > > > Still, device_pm_schedule_removal() can (in theory) be called concurrently > > > with dpm_resume() by another thread and this might corrupt the list without > > > the locking. > > > > Any thread doing that would be in violation of the restrictions you're > > going to add to the kerneldoc for destroy_suspended_device(). > > > > However the overhead for the locking isn't critical. There won't be > > any contention (if everything is working right) and it isn't a hot path > > anyway. So you can leave the extra locking in if you want. But then > > you should put it in all the routines where the lists get manipulated, > > not just some of them. That is: device_power_down(), dpm_power_up(), > > and even unregister_dropped_devices(). > > Except for those run on one CPU with interrupts disabled, I think. Not unregister_dropped_devices()! > > > > Also, the kerneldoc for destroy_suspended_device() should contain an > > > > extra paragraph warning that the routine should never be called except > > > > within the scope of a system sleep transition. In practice this means > > > > it has to be directly or indirectly invoked by a suspend or resume > > > > method. > > > > > > Or by a CPU hotplug notifier (that will be the majority of cases, IMO). > > > > In your patch the call is made in response to a CPU_UP_CANCELED_FROZEN > > notification. Isn't it true that this notification is issued only as > > part of a system sleep transition? > > Yes, it is. So it counts as being indirectly invoked by a resume method. Alan Stern _______________________________________________ linux-pm mailing list linux-pm@xxxxxxxxxxxxxxxxxxxxxxxxxx https://lists.linux-foundation.org/mailman/listinfo/linux-pm
