how to solve this multiple linux timer with single

Question

/*The handler checks that the value stored in sival_ptr matches a given timerID variable. The sival_ptr is the same as the one we set in makeTimer(), though here it lives in a different structure. Obviously, it got copied from there to here on the way to this signal handler. The point is that the timerID is what is used to determine which timer just went off and determine what to do next */

static void timerHandler( int sig, siginfo_t *si, void *uc )
{
    timer_t *tidp;

    tidp = si->si_value.sival_ptr;

    if ( *tidp == firstTimerID )

        TASK1(Task2ms_Raster);
   else if ( *tidp == secondTimerID )
       TASK2(Task10ms_Raster);
    else if ( *tidp == thirdTimerID )
        TASK3(Task100ms_Raster);
}

/* The function takes a pointer to a timer_t variable that will be filled with the timer ID created by timer_create(). This pointer is also saved in the sival_ptr variable right before calling timer_create(). In this function notice that we always use the SIGRTMIN signal, so expiration of any timer causes this signal to be raised. The signal handler I've written for that signal is timerHandler. */

 static int makeTimer( char *name, timer_t *timerID, int expireMS, int intervalMS )
{
     //sigset_t mask;
    struct sigevent         te;
    struct itimerspec       its;
    struct sigaction        sa;
    int                     sigNo = SIGRTMIN;

    /* Set up signal handler. */
    sa.sa_flags = SA_SIGINFO;
    sa.sa_sigaction = timerHandler;
    sigemptyset(&sa.sa_mask);
    if (sigaction(sigNo, &sa, NULL) == -1)
    {
        perror("sigaction");
    }

    /* Set and enable alarm */
    te.sigev_notify = SIGEV_SIGNAL;
    te.sigev_signo = sigNo;
    te.sigev_value.sival_ptr = timerID;
    timer_create(CLOCK_REALTIME, &te, timerID);

    its.it_interval.tv_sec = 0;
    its.it_interval.tv_nsec = intervalMS * 1000000;
    its.it_value.tv_sec = 0;
    its.it_value.tv_nsec = expireMS * 1000000;
    timer_settime(*timerID, 0, &its, NULL);


    return 1;
}

int main()
 {

     makeTimer("First Timer", &firstTimerID, 2, 2);   //2ms

   makeTimer("Second Timer", &secondTimerID, 10, 10);    //10ms
   makeTimer("Third Timer", &thirdTimerID, 100, 100);  //100ms


 }

I am using single handler to call the task for every 2ms, 10ms and 100ms. I am using multiple timers with single signal handler. How to identify which timer just went. In debug mode : the last debug control session is : static void timerHandler( int sig, siginfo_t *si, void *uc ){ . Could anyone help me how to solve this ?

Answer 1

Just use one timer every 2 msec and increment a counter. On every hit you have the 2 msec event, every 5th hit you also have the 10 msec event, and every 50th hit you also have the 100 msec event.

Note: the general solution is to have the timer hit every 1 msec and to have a list of timeouts to compare. They don't all have to be multiples of each other.