* Esben Nielsen <[email protected]> wrote:
> It can run within try_to_wake_up(). But then it the whole lock chain
> is traversed in an atomic section. That unpredictable overall system
> latencies since the locks can be in userspace. So it has to run in
> some task. That task has to be high priority enough to preempt the
> boosted tasks, but it can't be so high priority that it bothers any
> higher priority threads than those involved in this. So it can't be,
> forinstance a general priority 99 task we just use for this. We thus
> need something running at a slightly higher priority than the priority
> to which the tasks are boosted, but not a full +1 priority. I.e. we
> need to run it at priority "+0.5".
we could just queue the task in front of the other task in the runqueue,
and mark that task for reschedule if it's running currently. (Doing this
is not without precedent: we do something similar in wake_up_new_task()
to implement child-runs-first logic.)
Ingo
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