Linux timer CLOCK_PROCESS_CPU_ID is not working

Question

I need to use some timers in my code. I've got something like this:

    struct sigevent ec;

    ec.sigev_notify = SIGEV_THREAD;
    ec.sigev_value.sival_ptr = &c_timer;
    ec.sigev_notify_function = c_thread;
    ec.sigev_notify_attributes = NULL;

    secs = floor(c);
    nsecs = (long long) SECOND * (c - secs);
    printf("%ds\t%lldns\n\n",secs,nsecs);
    it1c.it_value.tv_sec = secs;
    it1c.it_value.tv_nsec = nsecs;
    it1c.it_interval.tv_sec = 0;
    it1c.it_interval.tv_nsec = 0;

    timer_create(CLOCK_PROCESS_CPUTIME_ID, &ec, &c_timer);
    timer_settime(c_timer, 0, &it1c, NULL);

Where c_thread is some simple function which is setting new timer, SECOND is:

#define SECOND 1000000000

c is something like 2.25

And my problem is that this timer doesn't call c_thread when it should. When i change CLOCK_PROCESS_CPUTIME_ID to CLOCK_REALTIME everything is ok, and it is called, but when I am using first one nothing happens. I am also checking CLOCK_PROCESS_CPUTIME_ID using other CLOCK_REALTIME timer with clock_gettime function and values of clock reach my it_value.

Any ideas what could be wrong?

And my second question: Is there any way to pass some arguments to function called as thread using timers?

Answer 1

@annamataris problem was not related to spinlock and nanosleep stuff. There is reason to use only CLOCK_REALTIME because.

The POSIX timers system calls first appeared in Linux 2.6. Prior to this, glibc provided an incomplete user-space implementation (CLOCK_REALTIME timers only) using POSIX threads, and in glibc versions before 2.17, the implementation falls back to this technique on systems running pre-2.6 Linux kernels.

Read man timer_create for more info.