[Xenomai-help] rtdm_event_timedwait returns -EINTR

["Petr Cervenka" <grugh@domain.hid>]

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Hello,
I have a problem with rtdm_event_timedwait() function. It sometimes ends prematurely with -EINTR error code. It depends on special circumstances (CPU load, resizing console window in X, ...).

I tried to create simple example with native skin to reproduce the behaviour. But the rt_event_wait() behaves differently.
It, insted of returning -EINTR, resets the timeout. It's like the function is called ones more after last interruption/unblock (with original timeout).

normal run:
------------------
event: res = -110 (Connection timed out)
time - actual 5.00001 s, wanted 5 s

window resizing
-------------------------
event: res = -110 (Connection timed out)
time - actual 14.9161 s, wanted 5 s

used versions:
----------------------
Linux rtc 2.6.26.3-adeos #1 SMP PREEMPT Tue Apr 14 15:03:35 CEST 2009 x86_64 GNU/Linux
Xenomai 2.4.7
adeos-ipipe-2.6.26-x86-2.0-17.patch

Thank you for any help or advice.

Petr Cervenka


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#include <sys/mman.h>
#include <native/task.h>
#include <native/event.h>
#include <native/timer.h>

#define MY_EVENT    0x00000001ll
#define MY_PRIORITY 99

static RT_TASK mainTask;

int main(int argc, char** argv) {
    const double ONE_SEC = 1e9;
    const RTIME timeout = (RTIME)(5 * ONE_SEC);
    RT_EVENT event;
    unsigned long mask;
    RTIME start, end;
    int res;

    mlockall(MCL_CURRENT | MCL_FUTURE);

    rt_task_shadow(&mainTask, NULL, MY_PRIORITY, T_FPU);

    rt_task_set_mode(0, T_PRIMARY, NULL);

    rt_event_create(&event, NULL, 0, EV_PRIO);

    start = rt_timer_read();
    res = rt_event_wait(&event, MY_EVENT, &mask, EV_ALL, rt_timer_ns2ticks(timeout));
    end = rt_timer_read();

    switch (res) {
        case -EINVAL:
        case -EIDRM:
        case -EWOULDBLOCK:
        case -EINTR:
        case -ETIMEDOUT:
        case -EPERM:
            printf("event: res = %d (%s)\n", res, strerror(-res));
            break;
        default:
            printf("unknown event: res = %d\n", res);
    }

    printf("time - actual %g s, wanted %g s\n", rt_timer_ticks2ns(end - start)/ONE_SEC, timeout/ONE_SEC);
    
    rt_event_delete(&event);

    return 0;
}