pthread_cond_wait:线程解开mutex指向的锁并被条件变量cond阻塞。
线程可以被函数pthread_cond_signal和函数 pthread_cond_broadcast唤醒线程
被唤醒后,它将重新检查判断条件是否满足,如果还不满足,
一般说来线程应该仍阻塞在这里,被等待被下一次唤醒。
编译和运行:
gcc -o pthread_cond pthread_cond.c -pthread
./pthread_cond
测试代码:pthread_cond.c
#include <pthread.h>
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
pthread_mutex_t mutex = PTHREAD_MUTEX_INITIALIZER; /*初始化互斥锁*/
pthread_cond_t cond = PTHREAD_COND_INITIALIZER; //初始化条件变量
void *thread1(void *);
void *thread2(void *);
int i=1;
int main(void)
{
pthread_t t_a;
pthread_t t_b;
pthread_create(&t_a,NULL,thread1,(void *)NULL); /*创建进程t_a*/
pthread_create(&t_b,NULL,thread2,(void *)NULL); /*创建进程t_b*/
pthread_join(t_b, NULL);/*等待进程t_b结束*/
pthread_mutex_destroy(&mutex);
pthread_cond_destroy(&cond);
exit(0);
}
void *thread1(void *junk)
{
for(i=1;i<=9;i++)
{
printf("thead1: IN one\n");
pthread_mutex_lock(&mutex);//
if(i%3==0)
pthread_cond_signal(&cond);/*条件改变,发送信号,通知t_b进程*/
else
printf("thead1: %d\n",i);
pthread_mutex_unlock(&mutex);//*解锁互斥量*/
printf("thead1: Up Mutex\n\n\n");
sleep(2);
}
}
void *thread2(void *junk)
{
while(i<9)
{
printf("thread2: IN two \n");
pthread_mutex_lock(&mutex);
/*
pthread_cond_wait:线程解开mutex指向的锁并被条件变量cond阻塞。
线程可以被函数pthread_cond_signal和函数 pthread_cond_broadcast唤醒线程
被唤醒后,它将重新检查判断条件是否满足,如果还不满足,
一般说来线程应该仍阻塞在这里,被等待被下一次唤醒
*/
if(i%3!=0)
pthread_cond_wait(&cond,&mutex);/*等待*/
printf("thread2: %d\n",i);
pthread_mutex_unlock(&mutex);
printf("thread2: Down Mutex\n");
sleep(2);
}
}
运行结果:
thread2: IN two
thead1: IN one
thead1: 1
thead1: Up Mutex
thead1: IN one
thead1: 2
thead1: Up Mutex
thead1: IN one
thread2: 3
thread2: Down Mutex
thead1: Up Mutex
thread2: IN two
thread2: 3
thread2: Down Mutex
thead1: IN one
thead1: 4
thead1: Up Mutex
thread2: IN two
thead1: IN one
thead1: 5
thead1: Up Mutex
thead1: IN one
thread2: 6
thread2: Down Mutex
thead1: Up Mutex
thread2: IN two
thread2: 6
thread2: Down Mutex
thead1: IN one
thead1: 7
thead1: Up Mutex
thread2: IN two
thead1: IN one
thead1: 8
thead1: Up Mutex
thead1: IN one
thread2: 9
thread2: Down Mutex
thead1: Up Mutex