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. > > > 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. > We wouldn't want to allow destroy_suspended_device() to be called when an > arbitrary CPU hotplug notification occurs. Of course. Greetings, Rafael - To unsubscribe from this list: send the line "unsubscribe linux-acpi" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
