条件锁pthread_cond_t - [Linux]

http://egeho123.blogbus.com/logs/10821816.html

2006年09月05日 12:42

说明， 等待线程 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 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 <stdio.h> #include <pthread.h> #include <unistd.h> pthread_mutex_t count_lock; pthread_cond_t count_nonzero; unsigned count = 0; void * decrement_count(void *arg) { pthread_mutex_lock (&count_lock); printf("decrement_count get count_lock\n"); while(count==0) { printf("decrement_count count == 0 \n"); printf("decrement_count before cond_wait \n"); pthread_cond_wait( &count_nonzero, &count_lock); printf("decrement_count after cond_wait \n"); } count = count -1; pthread_mutex_unlock (&count_lock); } void * increment_count(void *arg){ pthread_mutex_lock(&count_lock); printf("increment_count get count_lock\n"); if(count==0) { printf("increment_count before cond_signal\n"); pthread_cond_signal(&count_nonzero); printf("increment_count after cond_signal\n"); } count=count+1; pthread_mutex_unlock(&count_lock); } int main(void) { pthread_t tid1,tid2; pthread_mutex_init(&count_lock,NULL); pthread_cond_init(&count_nonzero,NULL); pthread_create(&tid1,NULL,decrement_count,NULL); sleep(2); pthread_create(&tid2,NULL,increment_count,NULL); sleep(10); pthread_exit(0); }