On Sun, 6 Jan 2008, Rafael J. Wysocki wrote: > > No -- the whole idea here is to print an error message in the system > > log if a driver's resume method tries to call device_del(). Deadlock > > is unavoidable in this case, but at least we'll know which driver is > > guilty. > > Still, if we do that, we won't need to acquire dev->sem in device_pm_remove() > any more. There's a window in lock_all_devices() when dpm_list_mtx isn't held. We don't want device_pm_remove() taking an already-locked device off the dpm_locked list at that time. So we do need to acquire dev->sem in device_pm_remove(). > Apart from this, by acqiring pm_sleep_rwsem for reading in > device_del() we can prevent a suspend from starting while the device is being > removed. > > Consider, for example, the scenario possible with the $subject patch: > - device_del() starts and notices pm_sleep_rwsem unlocked, so the warning is > not printed > - it proceeds and everything before device_pm_remove() succeeds > - now, device_suspend() is called and locks dev->sem > - device_del() calls device_pm_remove() and blocks on that with the device > partialy removed > I think we should prevent this from happening. I don't see anything wrong with it. All that will happen is that the removal will start before the suspend and finish after the resume. Alan Stern - 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
