POSIX之Condition Variable

int pthread_cond_init(pthread_cond_t *pCond, pthread_condattr_t *pAttr);
int pthread_cond_destroy(pthread_cond_t *pCond);

/* Vx6 Kernel */
typedef struct
    {
    int condAttrStatus;
    }pthread_condattr_t;

/* Vx6 RTP */
typedef struct
    {
    int condAttrStatus;
    clockid_t _CondAttrClockId;
    }pthread_condattr_t;

/* Vx7 */
typedef struct
    {
    int condAttrStatus;
    int condAttrPshared;
    unsigned int condAttrClockId;
    }pthread_condattr_t;

/*
 * condAttrStatus
 *   PTHREAD_INITIALIZED_OBJ - 默认值
 *   PTHREAD_DESTROYED_OBJ
 */
int pthread_condattr_init(pthread_condattr_t *pAttr);
int pthread_condattr_destroy(pthread_condattr_t *pAttr);

/*
 * condAttrClockId
 *   CLOCK_REALTIME - 默认值
 *   CLOCK_MONOTONIC
 */
int pthread_condattr_getclock(pthread_condattr_t *pAttr, clockid_t *pClockId);
int pthread_condattr_setclock (pthread_condattr_t *pAttr, clockid_t clockId);

/*
 * condAttrPshared
 *   PTHREAD_PROCESS_PRIVATE - 默认值
 *   PTHREAD_PROCESS_SHARED
 */
int pthread_condattr_getpshared (const pthread_condattr_t *pAttr, int *pShared);
int pthread_condattr_setpshared (pthread_condattr_t *pAttr, int shared);

/*
 * 这个函数释放pMutex，然后进入阻塞，等待其它Thread以Signal方式发送pCond，
 * 这个过程是一个原子操作。
 * 收到pCond后，此函数返回0，并再次lock pMutex。
 *
 * 如果收到其它Signal，此函数也返回0，这是一种虚假唤醒(Spurious Wakeup)，
 * 因此需要再判断相应数据的值
 *
 * 调用此函数的Thread必须先成功lock pMutex，否则此函数直接返回EINVAL
 */
int pthread_cond_wait(pthread_cond_t *pCond, pthread_mutex_t *pMutex);
/*
 * 与pthread_cond_wait()类似
 * 不过在阻塞到绝对时间pAbstime后，返回ETIMEDOUT
 */
int pthread_cond_timedwait(pthread_cond_t *pCond, pthread_mutex_t *pMutex, struct timespec *pAbstime);
/*
 * 将阻塞在pCond上的Thread置为Ready
 * 如果有多个Thread阻塞，则解除优先级最高的Thread
 * 如果没有Thread阻塞，则直接返回
 */
int pthread_cond_signal(pthread_cond_t *pCond);
/*
 * 将阻塞在pCond上的所有Thread置为Ready
 * 如果没有Thread阻塞，则直接返回
 */
int pthread_cond_broadcast(pthread_cond_t *pCond);

/*
 * 版权所有  公众号  VxWorks567
 */

#include <stdio.h>    /* printf() */
#include <unistd.h>   /* sleep() */
#include <pthread.h>  /* pthread_create() */
 
static pthread_mutex_t mutexid;
static pthread_cond_t condid;
static int data = 0;

static void *thread1(void *arg)
{
    pthread_mutex_lock(&mutexid);
    printf("\nCondition Variable: in thread1, pthread_mutex_lock\n");
    printf("Condition Variable: in thread1, data =  %d\n", data);

    printf("Condition Variable: in thread1, pthread_cond_wait begin\n\n");
    pthread_cond_wait(&condid, &mutexid);
    printf("\nCondition Variable: in thread1, pthread_cond_wait end\n\n");

    printf("Condition Variable: in thread1, data =  %d\n", data);

    pthread_mutex_unlock(&mutexid);
    printf("Condition Variable: in thread1, pthread_mutex_unlock\n");
    return NULL;
    }

static void *thread2(void *arg)
{
    sleep(1);
    pthread_mutex_lock(&mutexid);
    printf("\nCondition Variable: in thread2, pthread_mutex_lock\n");

    data = 1;
    printf("Condition Variable: in thread2, data =  %d\n", data);
    printf("Condition Variable: in thread2, pthread_cond_signal begin\n");
    pthread_cond_signal(&condid);
    printf("Condition Variable: in thread2, pthread_cond_signal end\n");

    printf("Condition Variable: in thread2, pthread_mutex_unlock begin\n");
    pthread_mutex_unlock(&mutexid);
    printf("Condition Variable: in thread2, pthread_mutex_unlock end\n");
    return NULL;
    }

int testPosixCond()
{
    pthread_t tid1;
    pthread_t tid2;

    sleep(1);

    pthread_mutex_init(&mutexid, NULL);
    pthread_cond_init(&condid, NULL);
    printf("\nCondition Variable: in main thread, pthread_mutex_init&pthread_cond_init\n");

    pthread_create(&tid1, NULL, &thread1, NULL);
    pthread_create(&tid2, NULL, &thread2, NULL);
    pthread_join(tid1, NULL);
    pthread_join(tid2, NULL);

    pthread_cond_destroy(&condid);
    pthread_mutex_destroy(&mutexid);
    printf("Condition Variable: in main thread, pthread_cond_destroy&pthread_mutex_destroy\n");
    return 0;
    }