Dmitry: I'm trying to help eliminate the need for the freezer during suspend. For it to work, we have to prevent threads which otherwise would have been frozen from trying to bind drivers to suspended devices or trying to register new devices whose parents are already suspended. To help accomplish this, the PM core can acquire the device semaphores for all existing devices before suspending any of them. That will prevent attempts at binding. It would also prevent registration of new children, _if_ the driver doing the registration had to acquire the parent's semaphore first. But many drivers don't do this. One thought was to have the PM core acquire and hold the dpm_list_mutex throughout the suspend. This would block registration attempts at the point where the new device is added to the PM core's device-list. Unfortunately it creates several lockdep violations. For example, the serio core holds serio->drv_mutex while input_register_device is called (which acquires dpm_list_mutex), and it acquires serio->drv_mutex in serio_suspend and serio_resume (which would be called while the PM core holds dpm_list_mutex). I'm having trouble coming up with a way to block registrations during suspend that won't create a possibility for deadlock. Do you have any suggestions? A scheme that would work for the input layer ought to be generally applicable. Alan Stern _______________________________________________ linux-pm mailing list linux-pm@xxxxxxxxxxxxxxxxxxxxxxxxxx https://lists.linux-foundation.org/mailman/listinfo/linux-pm
