[Xenomai] rtdm_timer_start latency?

Lowell Gilbert kludge at be-well.ilk.org
Fri Feb 9 15:50:30 CET 2018

Philippe Gerum <rpm at xenomai.org> writes:

> On 02/09/2018 11:02 AM, Philippe Gerum wrote:
>> On 02/09/2018 12:45 AM, Lowell Gilbert wrote:
>>> Am I correct in assuming that when calling rtdm_timer_start(), I should
>>> not be getting multi-second latencies before the first call to the timer
>>> routine? Just checking before I dig in too far.
>> Of course not. I suspect an absolute expiry time is given with a
>> relative mode spec.
> More generally, an absolute expiry time which is not based on the right
> clock specified by the mode argument.
> i.e.
> expiry = rtdm_clock_monotonic(), mode = RTDM_TIMERMODE_REALTIME => BAD
> expiry = rtdm_clock_realtime(), mode = RTDM_TIMERMODE_ABSOLUTE => BAD
> expiry = rtdm_clock_realtime() or _monotonic(), mode =

Okay, that makes sense.

I was using 0 for expiry, because I really just wanted the periodic
wakeup. I don't remember why I didn't create a periodic task instead of
using a timer.

What clock do I want to use to get the timer started? Once it starts, it
runs fine; but it often takes two or three seconds before the first call
into the handler.

To put it another way, I'm trying to figure out what am I doing wrong in:
		ret = rtdm_timer_start(&pstate.collect.timer, rtdm_clock_read() + 1,

Thanks again.

More information about the Xenomai mailing list