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.
If yes, then wakeups from signals don't work either, right?
Regards,
Peter Hurley
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