Hello,
I'm working on the creation of a Xenomai target for Mathwork's
Real Time Workshop. In order to achieve this, I would like to
control the execution rate of a task with a semaphore periodically
released by an alarm handler. The tasks does nothing else but waiting
(in a loop) on the semaphore. If the task can immediately take
the sempahore, it means that the rate is too fast for it because
the semaphore has been released before the end of its current iteration.
My problem is that I cannot decrease the alarm period under 40us
without facing this situation. I cannot figure what is the cause of
all that overhead (maybe it comes from the rt_alarm_wait call ?). I
have tried to use event flags instead of semaphores but I get the
same results.
Do you have any idea ?
Here is the code of the main task and the alarm handler:
void tBaseRate(void * cookie)
{
while (1) {
if (rt_sem_p(&rtClockSem, TM_NONBLOCK) == 0) {
printf("Rate for BaseRate task too fast.\n");
} else {
rt_sem_p(&rtClockSem, TM_INFINITE);
}
}
void clockHandler(void * cookie)
{
int status;
while (1) {
status = rt_alarm_wait(&clockDesc);
if (!status) {
status = rt_sem_v(&rtClockSem);
if (status)
printf ("Semaphore error : %d\n", status);
} else
printf ("Alarm error: %d\n", status);
}
}
Thank you very much.
Best regards,
Jean-Philippe Meylan
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