[Fwd: [rtl] dynamic periodic task ?]

[Bernhard Kuhn]

-- 
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| Bernhard Kuhn                (kuhn[at]lpr.ei.tum.de)  O|||OO||OO| |
| Laboratory for Process Control and Real-Time Systems  O|||O|O|O|O |
| Technische Universität München  Tel.+49-89-289-23732  O|||OO||OO| |
| 80290 München, Germany          Room 3944 Fax -23555  OOO|O|||O|O |
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---

Kay-Ulrich Scholl wrote:

> I created a periodic task but the period-time changes
> from time to time.
> The tak decides on his own when he wants to be recalled again.
> At the moment I do this in the following way:
> 
>  RTIME wait=last_send+wait_time-rt_get_time()-CAN_SEND_PERIOD;
>  // should I wait longer than CAN_SEND_PERIOD ?
>  if (wait>0)
>  {
>      long flags;
>      r_save_flags(flags);
>      r_cli();
>      // wait a litle bit longer next time:
>      can_send_task.resume_time=rt_get_time()+wait;
>      r_restore_flags(flags);
>  }
>  rt_task_wait();
> 
> Is there a better way ?



you may use

int rt_task_make_periodic(RT_TASK *task, RTIME start_time, RTIME period)

since that code is similar to yours (/usr/src/linux/kernel/rt_prio_sched.c):



int rt_task_make_periodic(RT_TASK *task, RTIME start_time, RTIME period)
{
        long flags;
        if (task->magic != RT_TASK_MAGIC) {
                return -EINVAL;
        }
        r_save_flags(flags);
        r_cli();
        task->resume_time = start_time;
        task->period = period;
        task->state = RT_TASK_DELAYED;
        r_restore_flags(flags);
        rt_schedule();
        return 0;
}





But you may also write write

   can_send_task.resume_time=rt_get_time()+wait;
   rt_task_wait();

since rt_task_wait() will reschedule anyway
(/usr/src/linux/kernel/rt_prio_sched.c):





int rt_task_wait(void)
{
        long flags;
        r_save_flags(flags);
        r_cli();
        rt_current->state = RT_TASK_DELAYED;
        rt_current->resume_time += rt_current->period;
        rt_schedule();
        r_restore_flags(flags);
        return 0;
}




-- 
 -------------------------------------------------------------------  
| Bernhard Kuhn                (kuhn[at]lpr.ei.tum.de)  O|||OO||OO| |
| Laboratory for Process Control and Real-Time Systems  O|||O|O|O|O |
| Technische Universität München  Tel.+49-89-289-23732  O|||OO||OO| |
| 80290 München, Germany          Room 3944 Fax -23555  OOO|O|||O|O |
 --------------------------------------------------------------------

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