Hi Bart, I too can't understand the problem. Perhaps you missed the fact that abort_exclusive_wait() does everything under wait_queue_head_t->lock ?
On 08/03, Bart Van Assche wrote: > > try_to_wake_up() locks task_struct.pi_lock but abort_exclusive_wait() not. > My assumption is that the following sequence of events leads to the lockup > that I had mentioned in the description of my patch: > * try_to_wake_up() is called for the task that will execute > abort_exclusive_wait(). > * After try_to_wake_up() has checked task_struct.state and before > autoremove_wake_function() has tried to remove the task from the wait > queue, abort_exclusive_wait() is executed for the same task. But we do not care if we race with another try_to_wake_up(), or even with another exclusive wake_up_nr(wq)/whatever unless wq is the same. And if this wq is the same, then wake_up_nr() will do try_to_wake_up/autoremove either before or after abort_exclusive_wait(), wake_up_nr() takes the same wq->lock. And this means that abort_exclusive_wait() can't be called "After try_to_wake_up()" and "before autoremove_wake_function()". Oleg.
