[Xenomai-help] periodical task in posix skin

[Xenomai-help] periodical task in posix skin

[ramon costa]

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Hi,

I have developed a very simple task in native code and it works fine
(included in native.tar.gz). This
simple task generates a square waveform through the parallel port ( and also
the speaker).

Currently I'm trying to transform this code into the POSIX skin (Makefile
and .c included in posix,tar.gz).
Unfortunatelly It does not work, although the parallel port shows a square
waveform its period is not the desired
one (0.1ms), its period is very small. This makes the system to freeze.

It seems that pthread_wait_np is not working properly, or may be I'm not
using pthread_make_periodic_np
properly. I used it in the following way :

        #define PERIOD 100000

        clock_gettime      ( CLOCK_REALTIME, &now);
        pthread_make_periodic_np (pthread_self(), &now, (struct timespec
*)PERIOD);

I also have tried

       struct timespec period;
       period.tv_sec=0;
       period.tv_nsec=PERIOD;

        clock_gettime      ( CLOCK_REALTIME, &now);
        pthread_make_periodic_np (pthread_self(), &now,&period);

Although both compile and execute, non of them works fine to me. Any clue ?


Best wishes,
Ramon

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Re: [Xenomai-help] periodical task in posix skin

[Gilles Chanteperdrix]

ramon costa wrote:
> Hi,
> 
> I have developed a very simple task in native code and it works fine
> (included in native.tar.gz). This
> simple task generates a square waveform through the parallel port ( and also
> the speaker).
> 
> Currently I'm trying to transform this code into the POSIX skin (Makefile
> and .c included in posix,tar.gz).
> Unfortunatelly It does not work, although the parallel port shows a square
> waveform its period is not the desired
> one (0.1ms), its period is very small. This makes the system to freeze.
> 
> It seems that pthread_wait_np is not working properly, or may be I'm not
> using pthread_make_periodic_np
> properly. I used it in the following way :
> 
>         #define PERIOD 100000
> 
>         clock_gettime      ( CLOCK_REALTIME, &now);
>         pthread_make_periodic_np (pthread_self(), &now, (struct timespec
> *)PERIOD);

Well, the reason why this does not work is obvious, I am even amazed
that it does not cause a segmentation fault, but you could check
pthread_make_periodic_np return value to have a clue.

> I also have tried
> 
>        struct timespec period;
>        period.tv_sec=0;
>        period.tv_nsec=PERIOD;
> 
>         clock_gettime      ( CLOCK_REALTIME, &now);
>         pthread_make_periodic_np (pthread_self(), &now,&period);
> 
> Although both compile and execute, non of them works fine to me. Any clue ?

Here I have no clue, more exactly, I would need to see the whole code to
see what is going wrong. But again, checking pthread_make_periodic_np
return value, and looking at the documentation would help. My guess
would be that at the time of pthread_make_periodic_np, "now" is a date
in the past.

And pthread_make_periodic_np/pthread_wait_np are supposed to help
porting code from RTLinux, they should not be used in new programs. You
should be using clock_gettime with the TIMER_ABSTIME flag.

-- 
					    Gilles.

Re: [Xenomai-help] periodical task in posix skin

[ramon costa]

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Hi,


>
> > I also have tried
> >
> >        struct timespec period;
> >        period.tv_sec=0;
> >        period.tv_nsec=PERIOD;
> >
> >         clock_gettime      ( CLOCK_REALTIME, &now);
> >         pthread_make_periodic_np (pthread_self(), &now,&period);
> >
> > Although both compile and execute, non of them works fine to me. Any clue
> ?
>
> Here I have no clue, more exactly, I would need to see the whole code to
> see what is going wrong. But again, checking pthread_make_periodic_np
> return value, and looking at the documentation would help. My guess
> would be that at the time of pthread_make_periodic_np, "now" is a date
> in the past.
>

Yes !!! You are completelly right !!

I was following RTLinux scheme and that made me to fail.
Current code is :

clock_gettime      ( TIMER_ABSTIME, &now);
now.tv_nsec=now.tv_nsec+PERIOD;
out=pthread_make_periodic_np (pthread_self(), &now,&period);
       switch(out){
         case 0 :
          break;
         case ESRCH:
        printf("thread is invalid \n");
        pthread_exit ((void *)-1);
          break;
         case ETIMEDOUT :
        printf("the start time has already passed\n");
        pthread_exit ((void *)-1);
          break;
         default :
        printf(" output value not defined \n");
            pthread_exit ((void *)-1);
    }




>
> And pthread_make_periodic_np/pthread_wait_np are supposed to help
> porting code from RTLinux, they should not be used in new programs. You
> should be using clock_gettime with the TIMER_ABSTIME flag.
>

This is very useful for porting from RTLinux which is exactly what I'm
doing.

Any suggestion to substitute pthread_make_periodic_np and  pthread_wait_np
in a POSIX skin ?



Thank you very much
Ramon

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Re: [Xenomai-help] periodical task in posix skin

[Gilles Chanteperdrix]

ramon costa wrote:
> Any suggestion to substitute pthread_make_periodic_np and  pthread_wait_np
> in a POSIX skin ?

clock_nanosleep with TIMER_ABSTIME.


-- 
					    Gilles.

Re: [Xenomai-help] periodical task in posix skin

[Ramon]

On 24/08/2010 14:13, Gilles Chanteperdrix wrote:
> ramon costa wrote:
>    
>> Any suggestion to substitute pthread_make_periodic_np and  pthread_wait_np
>> in a POSIX skin ?
>>      
> clock_nanosleep with TIMER_ABSTIME.
>
>
>    

Unfortunatelly,  clock_nanosleep is a relative delay while 
pthread_make_periodic_n is an absolute one, as a consequence the 
behaviour is different.

Ramon

Re: [Xenomai-help] periodical task in posix skin

[Gilles Chanteperdrix]

Ramon wrote:
> On 24/08/2010 14:13, Gilles Chanteperdrix wrote:
>> ramon costa wrote:
>>    
>>> Any suggestion to substitute pthread_make_periodic_np and  pthread_wait_np
>>> in a POSIX skin ?
>>>      
>> clock_nanosleep with TIMER_ABSTIME.
>>
>>
>>    
> 
> Unfortunatelly,  clock_nanosleep is a relative delay while 
> pthread_make_periodic_n is an absolute one, as a consequence the 
> behaviour is different.

TIMER_ABSTIME means absolute delay.

-- 
					    Gilles.

Re: [Xenomai-help] periodical task in posix skin

[Ramon]

Hi,

I'm sorry in my previous email I made an error.

If I use

clock_gettime      ( TIMER_ABSTIME, &now);
now.tv_nsec=now.tv_nsec+PERIOD;
out=pthread_make_periodic_np (pthread_self(), &now,&period);
......

it always says that "the start time has already passed\n". Differently 
if I use

clock_gettime      ( CLOCK_REALTIME, &now);
        now.tv_nsec=now.tv_nsec+PERIOD;
        out=pthread_make_periodic_np (pthread_self(), &now,&period);

  everything works fine.


Ramon