一尘不染

计时器和信号出现问题

linux

我已经使用timer_create()API实现了POSIX计时器,当计时器到期时,我将为其放置处理程序代码,这将生成SIGUSR1。现在的问题是,如果此程序收到另一个SIGUSR1,则将调用并捕获相同的信号处理程序。

有什么方法可以防止这种情况,以便处理程序可以捕获仅由计时器生成的信号?


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2020-06-03

共1个答案

一尘不染

这对您有用吗?(修改了timer_create手册页中示例中的代码。)

#include <stdlib.h>
#include <unistd.h>
#include <stdio.h>
#include <signal.h>
#include <time.h>

#define CLOCKID CLOCK_REALTIME
#define SIG SIGUSR1
timer_t timerid;


static void handler(int sig, siginfo_t *si, void *uc)
{
    if(si->si_value.sival_ptr != &timerid){
        printf("Stray signal\n");
    } else {
        printf("Caught signal %d from timer\n", sig);
    }
}

int main(int argc, char *argv[])
{
    struct sigevent sev;
    struct itimerspec its;
    long long freq_nanosecs;
    sigset_t mask;
    struct sigaction sa;

    printf("Establishing handler for signal %d\n", SIG);
    sa.sa_flags = SA_SIGINFO;
    sa.sa_sigaction = handler;
    sigemptyset(&sa.sa_mask);
    sigaction(SIG, &sa, NULL);

    sev.sigev_notify = SIGEV_SIGNAL;
    sev.sigev_signo = SIG;
    sev.sigev_value.sival_ptr = &timerid;
    timer_create(CLOCKID, &sev, &timerid);
    /* Start the timer */

    its.it_value.tv_sec = 10;
    its.it_value.tv_nsec = 0;
    its.it_interval.tv_sec = its.it_value.tv_sec;
    its.it_interval.tv_nsec = its.it_value.tv_nsec;

    timer_settime(timerid, 0, &its, NULL);
    sleep(100);
    exit(EXIT_SUCCESS);
}

当捕捉到来自定时器的信号时,Caught signal 10 from timer将显示。否则Stray signal将显示。

2020-06-03