Standard Library

#include <stdio.h>
#include <unistd.h>
#include <pthread.h>

#ifdef __cplusplus
#if __cplusplus
extern "C" {
#endif /* __cplusplus */
#endif /* __cplusplus */

#define THREAD_NUM 3
int g_startNum = 0; /* Number of started threads */
int g_wakenNum = 0; /* Number of wakeup threads */

struct testdata {
    pthread_mutex_t mutex;
    pthread_cond_t cond;
} g_td;

/*
 * Entry function of child threads.
 */
static void *ChildThreadFunc(void *arg)
{
    int rc;
    pthread_t self = pthread_self();

    /* Locks a mutex. */
    rc = pthread_mutex_lock(&g_td.mutex);
    if (rc != 0) {
        printf("ERROR:take mutex lock failed, error code is %d!\n", rc);
        goto EXIT;
    }

    /* The value of g_startNum is increased by 1. The value indicates the number of child threads that have locked a mutex. */
    g_startNum++;

    /* Wait for the condition variable. */
    rc = pthread_cond_wait(&g_td.cond, &g_td.mutex);
    if (rc != 0) {
        printf("ERROR: pthread condition wait failed, error code is %d!\n", rc);
        (void)pthread_mutex_unlock(&g_td.mutex);
        goto EXIT;
    }

    /* Attempt to lock a mutex, which is failed in normal cases. */
    rc = pthread_mutex_trylock(&g_td.mutex);
    if (rc == 0) {
        printf("ERROR: mutex gets an abnormal lock!\n");
        goto EXIT;
    }

    /* The value of g_wakenNum is increased by 1. The value indicates the number of child threads that have been woken up by the condition variable. */
    g_wakenNum++;

    /* Unlock a mutex. */
    rc = pthread_mutex_unlock(&g_td.mutex);
    if (rc != 0) {
        printf("ERROR: mutex release failed, error code is %d!\n", rc);
        goto EXIT;
    }
EXIT:
    return NULL;
}

static int testcase(void)
{
    int i, rc;
    pthread_t thread[THREAD_NUM];

    /* Initialize a mutex. */
    rc = pthread_mutex_init(&g_td.mutex, NULL);
    if (rc != 0) {
        printf("ERROR: mutex init failed, error code is %d!\n", rc);
        goto ERROROUT;
    }

    /* Initialize the condition variable. */
    rc = pthread_cond_init(&g_td.cond, NULL);
    if (rc != 0) {
        printf("ERROR: pthread condition init failed, error code is %d!\n", rc);
        goto ERROROUT;
    }

    /* Create child threads in batches. The number is specified by THREAD_NUM. */
    for (i = 0; i < THREAD_NUM; i++) {
        rc = pthread_create(&thread[i], NULL, ChildThreadFunc, NULL);
        if (rc != 0) {
            printf("ERROR: pthread create failed, error code is %d!\n", rc);
            goto ERROROUT;
        }
    }

    /* Wait until all child threads lock a mutex. */
    while (g_startNum < THREAD_NUM) {
        usleep(100);
    }

    /* Lock a mutex and block all threads using pthread_cond_wait. */
    rc = pthread_mutex_lock(&g_td.mutex);
    if (rc != 0) {
        printf("ERROR: mutex lock failed, error code is %d\n", rc);
        goto ERROROUT;
    }

    /* Unlock a mutex. */
    rc = pthread_mutex_unlock(&g_td.mutex);
    if (rc != 0) {
        printf("ERROR: mutex unlock failed, error code is %d!\n", rc);
        goto ERROROUT;
    }

    for (int j = 0; j < THREAD_NUM; j++) {
        /* Broadcast signals on the condition variable. */
        rc = pthread_cond_signal(&g_td.cond);
        if (rc != 0) {
            printf("ERROR: pthread condition failed, error code is %d!\n", rc);
            goto ERROROUT;
        }
    }

    sleep(1);

    /* Check whether all child threads are woken up. */
    if (g_wakenNum != THREAD_NUM) {
        printf("ERROR: not all threads awaken, only %d thread(s) awaken!\n", g_wakenNum);
        goto ERROROUT;
    }

    /* Wait for all threads to terminate. */
    for (i = 0; i < THREAD_NUM; i++) {
        rc = pthread_join(thread[i], NULL);
        if (rc != 0) {
            printf("ERROR: pthread join failed, error code is %d!\n", rc);
            goto ERROROUT;
        }
    }

    /* Destroy the condition variable. */
    rc = pthread_cond_destroy(&g_td.cond);
    if (rc != 0) {
        printf("ERROR: pthread condition destroy failed, error code is %d!\n", rc);
        goto ERROROUT;
    }
    return 0;
ERROROUT:
    return -1;
}

/*
 * Sample code main function
 */
int main(int argc, char *argv[])
{
    int rc;

    /* Start the test function. */
    rc = testcase();
    if (rc != 0) {
        printf("ERROR: testcase failed!\n");
    }

    return 0;
}
#ifdef __cplusplus
#if __cplusplus
}
#endif /* __cplusplus */
#endif /* __cplusplus */