pthreads之間的信號處理

Question

我正在嘗試學習進程和線程之間的信號處理。 幾個問題的答案將幫助我更好地理解它。

我知道進程可以向進程組發送信號並允許多個進程接收相同的信號，但我不確定線程​​。

• 發送到所有pthread的信號是否可以由多個pthread同時處理？

我設置我的程序使用pthread_sigmask()阻止所有信號，我有兩個線程使用sigwait(SIGUSR1)來等待信號，我有主線程發送SIGUSR1信號。 似乎只有一個線程處理信號時一切正常（我在另一個線程中注釋掉代碼），但是當兩個線程都在運行sigwait()代碼時，它會掛起或終止得太快。

代碼粘貼在下面。

sig_atomic_t signals = 0;
sig_atomic_t sigusr1_signals = 0;
sig_atomic_t sigusr2_signals = 0;
sig_atomic_t count = 0;
sig_atomic_t totalcount = 0;

sigset_t globalset;

int WAIT = 1;           /* false = 0, true = 1 */

static int SIGNALS_SENT = 0;
static int SIGNALS_RECEIVED = 0;

void *sig1handler1(void *argv);

void *reporterhandler(void *argv);

int random_number(int min, int max);

int main(void) {

    pthread_t threads[2];   /* create an array to store a number of threads */

    //int *p_status = &status;
    sigfillset(&globalset);
    pthread_sigmask(SIG_BLOCK, &globalset, NULL);

    /* Generate signal handling threads */
    if (pthread_create(&threads[0], NULL, &sig1handler1, NULL) > 0)
    {
        printf("Thread creation failure!\n");
        return -1;
    }


    /* create reporting thread */
    if (pthread_create(&threads[1], NULL, &reporterhandler, NULL) > 0)
    {
        printf("Thread creation failure!\n");
        return -1;
    }

    /* Signal all threads to begin work concurrently */
    WAIT = 0;

    int c = 0;
    while(c < 100)
    {
        int value = random_number(1, 2);
        if (value == 1)
            kill(0, SIGUSR1);
        else
            kill(0, SIGUSR2);

        SIGNALS_SENT++;
        c++;
        usleep(10000);
    }

    kill(0, SIGINT);


    /* Wait for each thread to finish and join */
    int i = 0;
    for(i = 0; i < 2; i++)
    {
        if (pthread_join(threads[i], NULL) > 0)
        {
            printf("Thread [%u] join failure!\n", (unsigned int)threads[i]);
            return -1;
        }

        printf("THREAD [%u] returned.\n", (unsigned int)threads[i]);
    }

    printf("Parent Process [%d] exiting successfully.\n", getpid());
    return EXIT_SUCCESS;
}


void *sig1handler1(void *argv)
{
    pthread_t tid = pthread_self();
    printf("THREAD[%u] sig1handler1: waiting for signal to do some work...\n", (unsigned int)tid);

//  sigset_t myset;
//  sigfillset(&myset);
//  sigdelset(&myset, SIGINT);
//  sigdelset(&myset, SIGUSR1);
//  pthread_sigmask(SIG_SETMASK, &myset, NULL);

    /* Wait for a signal to start work */
    while (WAIT);

    int sig;
    int count = 0;

    while(1)
    {
        sigwait(&globalset, &sig);
        if (sig == SIGUSR1)
        {
            sigusr1_signals++;
            signals++;
            count++;
            //printf("thread1: caught SIGUSR1 signal!\n");
        }
        else if (sig == SIGINT)
        {
            printf("thread1: caught SIGINT signal, detected SIGUSR1 %d times, and terminating!\n", count);          pthread_exit(NULL);
        }
    }

    //printf("THREAD[%u] sig1handler1: doing some work!\n", (unsigned int)tid);
    //return (void *)EXIT_SUCCESS;
    //return (void *)NULL;
    pthread_exit(NULL);
}

void *reporterhandler(void *argv)
{
    pthread_t tid = pthread_self();
    printf("THREAD[%u] reporter: waiting for signal to do some work...\n", (unsigned int)tid);

    int sig;
    int count = 0;

//  sigset_t myset;
//  sigfillset(&myset);
//  sigdelset(&myset, SIGINT);
//  sigdelset(&myset, SIGUSR1);
//  sigdelset(&myset, SIGUSR2);
//  pthread_sigmask(SIG_SETMASK, &myset, NULL);

    /* Wait for a signal to start work */
    while (WAIT);

    while(1)
    {
        sigwait(&globalset, &sig);
        if (sig == SIGUSR1)
        {
            sigusr1_signals++;
            signals++;
            count++;
            totalcount++;
            SIGNALS_RECEIVED++;
        }
        else if (sig == SIGUSR2)
        {
            sigusr2_signals++;
            signals++;
            count++;
            totalcount++;
            SIGNALS_RECEIVED++;
        }
        else if (sig == SIGINT)
        {
            printf("Reporter: SIGUSR1 detected %d times\n", sigusr1_signals);
            printf("Reporter: SIGUSR2 detected %d times\n", sigusr2_signals);
            printf("Reporter: detected %d signals\n", totalcount);
            printf("Reporter: SIGNALS_SENT %d \n", SIGNALS_SENT);
            printf("Reporter: SIGNALS_REC %d \n", SIGNALS_RECEIVED);
            pthread_exit(NULL);
        }

        /* Display Report after detecting 10 signals */
        if (count == 10)
                    sigusr1_signals, sigusr2_signals);

            count = 0;
        }
    }

    //printf("THREAD[%u] reporter: doing some work!\n", (unsigned int)tid);
    pthread_exit(NULL);
}

int random_number(int min, int max)
{
    if (min < max)
    {
        max = max + 1;      /* include the max value */
        return (rand() % (max - min)) + min;
    }

    return -1;
}   

Answer 1

• 可以將信號[be]發送到所有pthreads [和]同時由多個pthread處理嗎？

不是在同一時間。 這些是可能性：

1. 向進程發送信號（ kill() ）：在這種情況下，任何偵聽信號的線程都可以接收它，但只有一個可以接收它。
2. 向進程組發送信號：信號將傳遞到組中的所有進程。
3. 將信號發送到特定線程（ pthread_kill() ）：現在您將其發送到特定線程ID。

原型：

int pthread_kill(pthread_t thread, int sig);

在您的情況下，我認為將信號傳遞給所有線程的唯一方法是沿着所有線程ID迭代以使用pthread_kill()發送信號。