[uClinux-dev] real timer library on uClinux

[Will Huang]

Hi All,

I am working on Coldfire m5272c3 with uClinux version 2.6.17-uc1.

When I try to use the high resolution timer, I found that sometimes the program works well

but sometimes the timer will expire after double inteval time than the inteval time I have set

by using librt apis(timer_create, timer_settime).

Does anyone can help me?

Thank you very much!

 

PS: I have attached my program which is using the librt as bellow

 

#include <unistd.h>
#include <sys/types.h>
#include <stdio.h>
#include <sys/limits.h>
#include <time.h>
#include <sys/signal.h>
#include <sys/errno.h>

#define FAILURE -1
#define ABS     TIMER_ABSTIME
#define REL     0

sig_handler();
void timeaddval();

/*
 * Control Structure for Timer Examples
 */
struct timer_definitions {
        int type;                       /* Absolute or Relative Timer */
        struct sigevent evp;            /* Event structure */
        struct itimerspec timeout;      /* Timer interval */
};

/*
 * Initialize timer_definitions array for use in example as follows:
 *
 *   type, { sigev_value, sigev_signo }, { it_iteration, it_value }
 */

struct timer_definitions timer_values[TIMERS] = {
        { ABS, {0,SIGALRM}, {0,0, 3,0} },
        { ABS, {0,SIGUSR1}, {0,500000000, 2,0} },
        { REL, {0,SIGUSR2}, {0,0, 5,0} }
};

timer_t timerid;
volatile int usr1;
sigset_t mask;

main()
{
        int status;
        int clock_id = CLOCK_REALTIME;

        struct sigaction sig_act;
        struct timespec current_time;

        struct sigevent evp; 

        struct itimerspec timeout;

        evp.sigev_value = 0; 

        evp.sigev_signo = SIGUSR1;

        timeout.it_value.tv_sec = 2;
        timeout.it_value.tv_nsec = 0;
        timeout.it_interval.tv_sec = 3;
        timeout.it_interval.tv_nsec = 0;

        /*
         *  Initialize the sigaction structure for the handler.
         */

        sigemptyset(&mask);
        sig_act.sa_handler = (void *)sig_handler;
        sig_act.sa_flags = 0;
        sigemptyset(&sig_act.sa_mask);
        usr1 = 0;

        status = timer_create(clock_id, &evp,
                              &timerid);
        if (status == -1) {
                perror("timer_create");
                exit(-1);
        }
        sigaction(evp.sigev_signo, &sig_act, 0);

        status = clock_gettime(CLOCK_REALTIME, &current_time);
        timeaddval(&timeout.it_value, &current_time);
        status = timer_settime(timerid, TIMER_ABSTIME, &timeout, NULL);
        if (status == -1) {
                perror("timer_settime failed: ");
                exit(-1);
        }
}

/*
 *  Handle Timer expiration.
 */

sig_handler(signo)
int signo;
{
        if(signo = SIGUSR1)
              printf("timer expired\n");

        return;
}

/*
 * Add two timevalues: t1 = t1 + t2
 */

void timeaddval(t1, t2)
struct timespec *t1, *t2;
{
        t1->tv_sec += t2->tv_sec;
        t1->tv_nsec += t2->tv_nsec;
        if (t1->tv_nsec < 0) {
                t1->tv_sec--;
                t1->tv_nsec += 1000000000;
        }
        if (t1->tv_nsec >= 1000000000) {
                t1->tv_sec++;
                t1->tv_nsec -= 1000000000;
        }
}

 

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