linux-多執行緒

int pthread_cond_init (pthread_cond_t *__restrict __cond,
			      __const pthread_condattr_t *__restrict
			      __cond_attr);
int pthread_cond_destroy (pthread_cond_t *__cond);

 pthread_cond_wait (pthread_cond_t *__restrict __cond,
			      pthread_mutex_t *__restrict __mutex)

int pthread_cond_signal (pthread_cond_t *__cond);

int pthread_cond_broadcast (pthread_cond_t *__cond)

#include <stdio.h>
#include <stdlib.h>
#include <pthread.h>
#include <unistd.h>
#include <string.h>
#define DEBUG 1

int num=0;
pthread_mutex_t mylock=PTHREAD_MUTEX_INITIALIZER;
pthread_cond_t qready=PTHREAD_COND_INITIALIZER;
void * thread_func(void *arg)
{
    int i=(int)arg; 
    int ret;
    sleep(5-i);//執行緒睡眠,然最先生成的執行緒，最後甦醒
    pthread_mutex_lock(&mylock);//呼叫pthread_cond_wait前，必須獲得互斥鎖
    while(i!=num)
    {
#ifdef DEBUG
        printf("thread %d waiting\n",i);
#endif
        ret=pthread_cond_wait(&qready,&mylock);//該函式把執行緒放入等待條件的執行緒列表，然後對互斥鎖進行解鎖，這兩部都是原子操作。並且在pthread_cond_wait返回時，互斥量再次鎖住。
        if(ret==0)
        {
#ifdef DEBUG
            printf("thread %d wait success\n",i);
#endif
        }else
        {
#ifdef DEBUG
            printf("thread %d wait failed:%s\n",i,strerror(ret));
#endif
        }
    }
    printf("thread %d is running \n",i);
    num++;
    pthread_mutex_unlock(&mylock);//解鎖
    pthread_cond_broadcast(&qready);//喚醒等待該條件的所有執行緒
    return (void *)0;
}
int main(int argc, char** argv) {
    
    int i=0,err;
    pthread_t tid[4];
    void *tret;
    for(;i<4;i++)
    {
        err=pthread_create(&tid[i],NULL,thread_func,(void *)i);
        if(err!=0)
        {
            printf("thread_create error:%s\n",strerror(err));
            exit(-1);
        }
    }
    for (i = 0; i < 4; i++)
    {
        err = pthread_join(tid[i], &tret);
        if (err != 0)
        {
            printf("can not join with thread %d:%s\n", i,strerror(err));
            exit(-1);
        }
    }
    return 0;
}