Deadline miss in periodic tasks

Joel Sherrill joel.sherrill at
Fri Sep 7 14:01:40 UTC 2012

On 09/07/2012 02:14 AM, Fered wrote:
> Hi;
> In periodic tasks, if a task misses its deadline at middle of its execution,
> is the task stopped or it continues and just the rtems_rate_monotonic_period()
> function returns RTEMS_TIMEOUT?
If you are using the Deterministic Priority Scheduler (default)
or the Earliest Deadline First, this is the case.

If you are using the Constant Bandwidth Scheduler algorithm,
then it can detect when a thread is not going to make its
deadline and give you options to deal with that.

But in general, the task continues to execute after the period.
There is no magic way for RTEMS to make you go back to
the top of the loop without the user callbacks supported by the
CBS algorithm. When you get the RTEMS_TIMEOUT, you have
to know what that means to that task.
> Thanks.
> _______________________________________________
> rtems-users mailing list
> rtems-users at

Joel Sherrill, Ph.D.             Director of Research&   Development
joel.sherrill at        On-Line Applications Research
Ask me about RTEMS: a free RTOS  Huntsville AL 35805
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