使用pthread_exit和pthread_join。 pthread_exit不会终止调用函数

Question

gcc 4.6.0 c89

I am just experimenting with using pthread_exit and pthread_join.

The only thing I notice with the pthread_exit it that it didn't display the print message before main returned. However, pthread_join did exactly that.

I would have thought the print statement should have been displayed. If not does that mean that main has not terminated correctly in using the pthread_exit?

Many thanks for any suggestions,

My source code snippet source.c file:

void* process_events(void)
{
    app_running = TRUE;
    int counter = 0;

    while(app_running) {
#define TIMEOUT 3000000
        printf("Sleeping.....\n");
        usleep(TIMEOUT);

        if(counter++ == 2) {
            app_running = FALSE;
        }
    }

    printf("Finished process events\n");

    return NULL;
}

Source code snippet main.c file:

int main(void)
{
    pthread_t th_id = 0;
    int th_rc = 0;

    th_rc = pthread_create(&th_id, NULL, (void*)process_events, NULL);
    if(th_rc == -1) {
        fprintf(stderr, "Cannot create thread [ %s ]\n", strerror(errno));
        return -1;
    }

    /*
     * Test with pthread_exit and pthread_join
     */

    /* pthread_exit(NULL); */

    if(pthread_join(th_id, NULL) == -1) {
        fprintf(stderr, "Failed to join thread [ %s ]", strerror(errno));
        return -1;
    }

    printf("Program Terminated\n");

    return 0;
}

Answer 1

What you're seeing is expected. pthread_exit never returns. It stops the thread that calls it immediately (and then runs the clean-up handlers if any, and then potentially thread-specific data destructors).

Nothing in main after pthread_exit will ever run.