> Benjamin LaHaise writes:
> > current->state = TASK_INTERRUPTIBLE;
> > add_wait_queue(&my_wait_queue, &wait);
>
> That should be:
> add_wait_queue(&my_wait_queue, &wait);
> current->state = TASK_INTERRUPTIBLE;
>
> otherwise there is a chance that the interrupt could occur between
> the TASK_INTERRUPTIBLE and the add_wait_queue. If this does happen,
> the task will not be on my_wait_queue, and therefore the state will
> not be set to TASK_RUNNING.
Ummm, no, that's worse and a different kind of race: you'll note that in
the original code I posted, the trigger for the wake up should be
started *after* the add_wait_queue. With your change, what happens if
someone else had already triggered the interrupt and it does a wake_up
between the add_wait_queue and current->state = TASK_INTERRUPTIBLE? The
task will then sleep until the wait queue gets another
wake_up_interruptible or a signal arrives for the task, which is wrong.
-ben
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