On Thu, Oct 02, 2014 at 09:49:04AM -0400, Peter Hurley wrote:
> On 10/02/2014 08:42 AM, Peter Zijlstra wrote:
> > On Thu, Oct 02, 2014 at 02:31:50PM +0200, Peter Zijlstra wrote:
> >> @@ -2086,24 +2086,22 @@ static void rfcomm_kill_listener(void)
> >>
> >> static int rfcomm_run(void *unused)
> >> {
> >> + DEFINE_WAIT_FUNC(wait, woken_wake_function);
> >> BT_DBG("");
> >>
> >> set_user_nice(current, -10);
> >>
> >> rfcomm_add_listener(BDADDR_ANY);
> >>
> >> - while (1) {
> >> - set_current_state(TASK_INTERRUPTIBLE);
> >> -
> >> - if (kthread_should_stop())
> >> - break;
> >> + add_wait_queue(&rfcomm_wq, &wait);
> >> + while (!kthread_should_stop()) {
> >>
> >> /* Process stuff */
> >> rfcomm_process_sessions();
> >>
> >> - schedule();
> >> + wait_woken(&wait, TASK_INTERRUPTIBLE, MAX_SCHEDULE_TIMEOUT);
> >> }
> >> - __set_current_state(TASK_RUNNING);
> >> + remove_wait_queue(&rfcomm_wq, &wait);
> >>
> >> rfcomm_kill_listener();
> >>
> >
> > Hmm, I think there's a problem there. If someone were to do
> > kthread_stop() before wait_woken() we'd not actually stop, because
> > wait_woken() doesn't test KTHREAD_SHOULD_STOP before calling schedule().
>
> Do you mean this situation?
>
> CPU 0 | CPU 1
> |
> rfcomm_run() | kthread_stop()
> ... |
> if (!test_bit(KTHREAD_SHOULD_STOP)) |
> | set_bit(KTHREAD_SHOULD_STOP)
> | wake_up_process()
> wait_woken() | wait_for_completion()
> set_current_state(INTERRUPTIBLE) |
> if (!WQ_FLAG_WOKEN) |
> schedule_timeout() |
> |
>
> Now both tasks are sleeping forever.
Yep.
> If yes, then wakeups from signals don't work either, right?
Its a kthread, there should not be any signals.
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