Re: [Xenomai-help] Problems with rt_task_wait_period

[Philippe Gerum <rpm@xenomai.org>]

On Mon, 2006-08-07 at 15:45 +0200, Jan Kiszka wrote:
> Steve Kreyer wrote:
> > Hi,
> > 
> > Iam new to xenomai. 
> > For warming up I try to run this little test program:
> > 
> > -----------------------------------------------------------------------
> > #include <native/task.h>
> > #include <stdio.h>
> > #include <sys/mman.h>
> > 
> > RT_TASK task1;
> > 
> > void rt_task1(void* user_data){
> >     int err = 0;
> >     printf("%d\n", rt_task_set_periodic(NULL, TM_NOW, 100));
> 
> You are running in one-shot mode, thus all time units are in
> *nanoseconds*. 100 ns cycles tend to pass quite quickly, thus the setup
> actually fails (but it doesn't report this - a corner case for
> considering this a bug).

The setup does not really fail, but the period is so short that the tick
occurs before the task has a chance to wait for the first release point
in the timeline, so rt_task_wait_period() notices that no timer is
outstanding, but incorrectly concludes that no timer was ever armed.

> 
> >     err = rt_task_wait_period(NULL);
> >     if(err){
> >         fprintf(stderr, "Cannot wait periodic: %d, %d\n", err, EWOULDBLOCK);
> > 
> >     }
> > }
> > 
> > int main(){
> >     char* task1_data = NULL;
> >     mlockall(MCL_CURRENT|MCL_FUTURE);
> >     rt_timer_set_mode(TM_ONESHOT);
> >     rt_task_spawn(&task1, "task1", 0, 99, 0, rt_task1, &task1_data);
> >     sleep(10);
> >     rt_task_delete(&task1);
> >     return 0;
> > }
> > -----------------------------------------------------------------------
> > 
> > But rt_task_wait_period gives me always the Error EWOULDBLOCK, which means that I did not set the task periodic
> > but which in fact I did... The call to rt_task_set_periodic is succesful.
> > Can anyone help me figure out why? If you need additional infos please let me know...
> > 
> > Thanks in advance!
> > 
> > Steve
> > 
> 
> Jan
> 
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-- 
Philippe.