Re: [patch] Real-Time Preemption, -RT-2.6.10-rc2-mm3-V0.7.32-6

[Ingo Molnar <mingo@elte.hu>]

* K.R. Foley <kr@cybsft.com> wrote:

> running realfeel with rtc histogram generates > 100 usec entries in
> the histogram but none of these are ever caught by the wakeup tracing.

can you reproduce this with rtc_wakeup:

  http://www.affenbande.org/~tapas/wiki/index.php?rtc_wakeup

?

> I think I know why we don't get traces from this. TIF_NEED_RESCHED is
> not set for IRQ 8 at the time that it wakes up realfeel so
> _need_resched fails and trace_start_sched_wakeup doesn't actually call
> __trace_start_sched_wakeup(p)???

here's the code:

+static inline void trace_start_sched_wakeup(task_t *p, runqueue_t *rq)
+{
+       if (TASK_PREEMPTS_CURR(p, rq) && (p != rq->curr) && _need_resched())
+               __trace_start_sched_wakeup(p);
+}

indeed this only triggers if the woken up task has a higher priority
than the waker... hm. Could you try to reverse the priorities of 
realfeel and IRQ8, does that produce traces?

	Ingo