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* [Xenomai-help] Problem of thread creation with Xenomai Posix
@ 2008-02-14 13:32 Fabien MAHOT
  2008-02-14 13:46 ` Gilles Chanteperdrix
  2008-02-14 13:48 ` Johan Borkhuis
  0 siblings, 2 replies; 6+ messages in thread
From: Fabien MAHOT @ 2008-02-14 13:32 UTC (permalink / raw)
  To: xenomai

Hi,

I need your help to understand why my application doesn't work correctly.

I use the Xenomai 2.3.4 kernel with its POSIX skin to develop a real time
application. In this program, I create several threads thanks to a main
thread which has the highest priority (SCHED_FIFO configuration). The aim
is that the main thread stays in execution during the creation of all the
other threads.

However, in my program, when the main thread calls the posix function
pthread_create to create a new thread, it's preempted by a thread created
previously. In spite of the main thread has the highest priority.

To illustrate my problem, I wrote a test program. I execute this
application in my xenomai environment and in a linux environment (linux
2.6.20 kernel configured preemptive)  :

My test program : The main function creates Main Thread. After Main Thread
creates T1 thread and next T2 thread. Main priority : 30, T1 priority :
25, T2 priority : 20.


#include <sys/mman.h>
#include <pthread.h>
#include <unistd.h>
#include <sys/time.h>
#include <string.h>
#include <stdio.h>

void console(char * chaine)
{
	write(2, chaine, strlen(chaine));
	fflush(stderr);
}

int func(volatile int* i)
{
	return (*i)++;
}

void* thread1(void * context) {
        volatile int i;
	volatile int result;

	console("T1 : start\n");
        while (i < 10000) {
              result = func(&i);
        }
	console("T1 : finish\n");

	return NULL;
}

void* thread2(void * context) {
        volatile int i;
	volatile int result;

	console("T2 : start\n");
        while (i < 10000) {
              result = func(&i);
        }
	console("T2 : finish\n");

	return NULL;
}

void* thread_main(void *arg) {
    	pthread_attr_t attr;
    	pthread_t p1;
    	pthread_t p2;
    	struct sched_param sch;
    	struct sched_param sch1;
    	int result;

        pthread_attr_init(&attr);
        pthread_attr_setinheritsched(&attr,PTHREAD_EXPLICIT_SCHED);
	pthread_attr_setschedpolicy(&attr, SCHED_FIFO);

        sch.sched_priority = 25;
        pthread_attr_setschedparam(&attr, &sch);

	console("M : before pthread_create T1\n");
        pthread_create(&p1, &attr, thread1, NULL);
	console("M : after pthread_create T1\n");

        sch.sched_priority = 20;
        pthread_attr_setschedparam(&attr, &sch);

	console("M : before pthread_create T2\n");
        result = pthread_create(&p2, &attr, thread2, NULL);
	if (result != 0)
	{
		console("creation of thread 2 impossible\n");
	}
	console("M : after pthread_create T2\n");

        pthread_attr_destroy(&attr);

        while (1) {
                sleep(500);
        }
	return NULL;
}

int main(int argc, char** argv) {
   	pthread_attr_t attr;
        pthread_t p;
    	struct sched_param sch;

       	mlockall(MCL_CURRENT|MCL_FUTURE);

        pthread_attr_init(&attr);
	pthread_attr_setinheritsched(&attr,PTHREAD_EXPLICIT_SCHED);
        pthread_attr_setschedpolicy(&attr, SCHED_FIFO);

        sch.sched_priority = 30;
        pthread_attr_setschedparam(&attr, &sch);
        pthread_create(&p, &attr, thread_main, NULL);
        pthread_attr_destroy(&attr);

        while (1) {
                sleep(500);
        }

        return 0;
}



Result in Linux environment :

M : before pthread_create T1
M : after pthread_create T1
M : before pthread_create T2
M : after pthread_create T2
T1 : start
T1 : finish
T2 : start
T2 : finish

Result in Xenomai environment :

M : before pthread_create T1
M : after pthread_create T1
M : before pthread_create T2
T1 : start
T1 : finish
M : after pthread_create T2
T2 : start
T2 : finish

In the Linux environment, the thread creation is correct, Main thread is
not preempted by T1.
But in the Xenomai environment, we can see that Main thread is preempted
by T1 thread during the T2 creation.

I would like to know why I ve got this problem with Xenomai. If you ve got
an idea, please , give me your opinion.

Thanks a lot.



^ permalink raw reply	[flat|nested] 6+ messages in thread
end of thread, other threads:[~2008-02-14 15:10 UTC | newest]

Thread overview: 6+ messages (download: mbox.gz follow: Atom feed
-- links below jump to the message on this page --
2008-02-14 13:32 [Xenomai-help] Problem of thread creation with Xenomai Posix Fabien MAHOT
2008-02-14 13:46 ` Gilles Chanteperdrix
2008-02-14 13:48 ` Johan Borkhuis
2008-02-14 13:51   ` Gilles Chanteperdrix
2008-02-14 14:55     ` Johan Borkhuis
2008-02-14 15:10       ` Gilles Chanteperdrix

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