[Xenomai-help] Sporadic PC freeze after rt_task_start

["M. Koehrer" <mathias_koehrer@domain.hid>]

Hi everybody,

I noticed a sporadic freeze of my PC using Xenomai 2.3.1 and kernel 2.6.20.4 on a Pentium D.
adeos-ipipe-2.6.20-i386-1.8-01.patch.

The freeze happened sporadically on one of our systems, occasionally it took up to 6 hours  to get it.
Using a PCI Post Code board and writing POST codes to it, I was able to locate the code that was causing
the issue. And finally I was able to extract it to a very simple program that shows the same behaviour!!

Here is my simple test program:
**************************************** BEGIN *****************
#include <stdio.h>
#include <sys/mman.h>

#include <native/task.h>
#include <native/sem.h>


RT_TASK taska_desc;

void mytaska(void *cookie)
{
    int i;

    for (i=0; i < 5; i++)
    {
        rt_task_sleep(5000000);
    }
}

int main(void)
{
    int i;
    int j;
    mlockall(MCL_CURRENT|MCL_FUTURE);

    for (j=0; j < 100; j++)
        for (i=10; i < 15000; i++)
        {
            rt_task_create(&taska_desc, "mytaska", 0, 81, T_JOINABLE | T_FPU | T_CPU(1));
            rt_task_start(&taska_desc, &mytaska, NULL);
            usleep(1500);

            rt_task_join(&taska_desc);
            if ( i % 100 == 0)
                printf("Loop %i\n", i);
        }

    return 0;
}
*************************************** END ***********************************
It is important to know, that I started the kernel with isolcpus=1, i.e. all non-realtime tasks
are running on CPU 0.
Somehow it seems to have to do with the usleep() that is following the rt_task_start.
usleep() is executed on CPU 0 and rt_task_start starts a task on CPU 1...
Can this be as the begin of usleep() is executed before the task is started but the end of
usleep() is when the task has already started. Could this be a cause for a race condition?

I leave the program running for a while and somehow it freezes the PC (only reset works).

Any feedback on this is welcome!

Regards

Mathias






-- 
Mathias Koehrer
mathias_koehrer@domain.hid


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