sigev_thread.c

/*
 * sigev_thread.c
 *
 * Demonstrate use of the SIGEV_THREAD signal mode to handle
 * signals by creating a new thread.
 *
 * Special notes: This program will not compile on Solaris 2.5.
 * It will compile on Digital UNIX 4.0 but will not work.
 * Digital UNIX 4.0D fixes SIGEV_THREAD, and sources inform me
 * that Solaris 2.6 will also fix SIGEV_THREAD. To try this on
 * Solaris, remove the "#ifdef sun" conditionals in main.
 */
#include <pthread.h>
#include <signal.h>
#include <sys/time.h>
#include "errors.h"

timer_t timer_id;
pthread_mutex_t mutex = PTHREAD_MUTEX_INITIALIZER;
pthread_cond_t cond = PTHREAD_COND_INITIALIZER;
int counter = 0;

/*
 * Thread start routine to notify the application when the
 * timer expires. This routine is run "as if" it were a new
 * thread, each time the timer expires.
 *
 * When the timer has expired 5 times, the main thread will
 * be awakened, and will terminate the program.
 */
void
timer_thread (union sigval si)
{
    int status;

    status = pthread_mutex_lock (&mutex);
    if (status != 0)
        err_abort (status, "Lock mutex");
    if (++counter >= 5) {
        status = pthread_cond_signal (&cond);
        if (status != 0)
            err_abort (status, "Signal condition");
    }
    status = pthread_mutex_unlock (&mutex);
    if (status != 0)
        err_abort (status, "Unlock mutex");

    printf ("Timer (0x%p) %d\n", si.sival_ptr, counter);
}

int main()
{
    int status;
    struct itimerspec ts;
    struct sigevent se;

#ifdef sun
    fprintf (
        stderr,
        "This program cannot compile on Solaris 2.5.\n"
        "To build and run on Solaris 2.6, remove the\n"
        "\"#ifdef sun\" block in main().\n");
#else
    /*
     * Set the sigevent structure to cause the signal to be
     * delivered by creating a new thread.
     */
    se.sigev_notify = SIGEV_THREAD;
    se.sigev_value.sival_ptr = &timer_id;
    se.sigev_notify_function = timer_thread;
    se.sigev_notify_attributes = NULL;

    /*
     * Specify a repeating timer that fires each 5 seconds.
     */
    ts.it_value.tv_sec = 5;
    ts.it_value.tv_nsec = 0;
    ts.it_interval.tv_sec = 5;
    ts.it_interval.tv_nsec = 0;

    DPRINTF (("Creating timer\n"));
    status = timer_create(CLOCK_REALTIME, &se, &timer_id);
    if (status == -1)
        errno_abort ("Create timer");

    DPRINTF ((
        "Setting timer %d for 5-second expiration...\n", timer_id));
    status = timer_settime(timer_id, 0, &ts, 0);
    if (status == -1)
        errno_abort ("Set timer");

    status = pthread_mutex_lock (&mutex);
    if (status != 0)
        err_abort (status, "Lock mutex");
    while (counter < 5) {
        status = pthread_cond_wait (&cond, &mutex);
        if (status != 0)
            err_abort (status, "Wait on condition");
    }
    status = pthread_mutex_unlock (&mutex);
    if (status != 0)
        err_abort (status, "Unlock mutex");

#endif /* Sun */
    return 0;
}