linux条件锁pthread_cond_t使用示例

等待线程[喝小酒的网摘]http://blog.hehehehehe.cn/a/17163.htm

1。使用pthread_cond_wait前要先加锁

2。pthread_cond_wait内部会解锁，然后等待条件变量被其它线程激活(pthread_cond_signal发送信号)

3。pthread_cond_wait被激活后会再自动加锁

激活线程：

1。加锁（和等待线程用同一个锁）

2。pthread_cond_signal发送信号

3。解锁

激活线程的上面三个操作在运行时间上都在等待线程的pthread_cond_wait函数内部。

程序示例：

#include <stdlib.h>

#include <stdio.h>

#include <string.h>

#include <pthread.h>

pthread_mutex_t lock;

pthread_cond_t cond;

int sum;

void* dec(void *argv)

{

pthread_mutex_lock(&lock);

while(sum==0)

{

printf("dec sum=0 ");

pthread_cond_wait(&cond,&lock);

}

sum--;

pthread_mutex_unlock(&lock);

printf("dec sum=%d ",sum);

pthread_exit(NULL);

return 0;

}

void* add(void *argv)

{

pthread_mutex_lock(&lock);

if(sum==0)

{

printf("add sum =0 ");

pthread_cond_signal(&cond);

}

sum++;

pthread_mutex_unlock(&lock);

sleep(1);

sum++;

printf("add sum=%d ",sum);

pthread_exit(NULL);

return 0;

}

int main(int argc,char** argv)

{

pthread_t ptid1,ptid2;

sum = 0;

pthread_mutex_init(&lock,NULL);

pthread_cond_init(&cond,NULL);

pthread_create(&ptid1,NULL,dec,NULL);

pthread_create(&ptid2,NULL,add,NULL);

int counter = 0;

while(counter != 10){

printf("counter: %d ", counter);

sleep(1);

counter++;

}

return 0;

}

运行结果：

dec sum=0

counter: 0

add sum =0

dec sum=0

add sum=1

counter: 1

counter: 2

counter: 3

counter: 4

counter: 5

counter: 6

counter: 7

counter: 8

counter: 9

[喝小酒的网摘]http://blog.hehehehehe.cn/a/17163.htm