java mutex命令_互斥量mutex的简单使用(实例讲解)
几个重要的函数：
#include
int pthread_mutex_init(pthread_mutex_t *restrict mutex, const pthread_mutex_t *restrict attr); //初始化mutex
int pthread_mutex_destroy(pthread_mutex_t *mutex); //如果mutex是动态分配的，则释放内存前调用此函数。
int pthread_mutex_lock(pthread_mutex_t *mutex); //加锁
int pthread_mutex_trylock(pthread_mutex_t *mutex); //若已有其他线程占用锁，则返回EBUSY，否则返回0，不阻塞。
int pthread_mutex_unlock(pthread_mutex_t *mutex); //解锁
例程：
复制代码 代码如下:
#include
#include
#include
#include
#include
int a = 100;
int b = 200;
pthread_mutex_t lock;
void * threadA()
{
pthread_mutex_lock(&lock);
printf("thread A got lock! ");
a -= 50;
sleep(3); //如果不加锁，threadB输出会是50和200
b += 50; //加锁后会sleep 3秒后，并为b加上50 threadB才能打印
pthread_mutex_unlock(&lock);
printf("thread A released the lock! ");
a -= 50;
}
void * threadC()
{
sleep(1);
while(pthread_mutex_trylock(&lock) == EBUSY) //轮询直到获得锁
{
printf("thread C is trying to get lock! ");
usleep(100000);
}
printf("thread C got the lock! ");
a = 1000;
b = 2000;
pthread_mutex_unlock(&lock);
printf("thread C released the lock! ");
}
void * threadB()
{
sleep(2); //让threadA能先执行
pthread_mutex_lock(&lock);
printf("thread B got the lock! a=%d b=%d ", a, b);
pthread_mutex_unlock(&lock);
printf("thread B released the lock! ", a, b);
}
int main()
{
pthread_t tida, tidb, tidc;
pthread_mutex_init(&lock, NULL);
pthread_create(&tida, NULL, threadA, NULL);
pthread_create(&tidb, NULL, threadB, NULL);
pthread_create(&tidc, NULL, threadC, NULL);
pthread_join(tida, NULL);
pthread_join(tidb, NULL);
pthread_join(tidc, NULL);
return 0;
}
时间： 2014-01-20
几个重要的函数： #include int pthread_mutex_init(pthread_mutex_t *restrict mutex, const pthread_mutex_t *restrict attr); //初始化mutex int pthread_mutex_destroy(pthread_mutex_t *mutex); //如果mutex是动态分配的，则释放内存前调用此函数。 int pthread_mutex_lock(pthread_mutex_t *mutex); //加锁 int pthread_mutex_trylock(pthread_mutex_t *mutex); //若已有其他线程占用锁，则返回EBUSY，否则返回0，不阻塞。 int pthread_mutex_unlock(pthread_mutex_t *mutex); //解锁 例程： 复制代码 代码如下: #include #include #include #include #include int a = 100; int b = 200; pthread_mutex_t lock; void * threadA() { pthread_mutex_lock(&lock); printf("thread A got lock! "); a -= 50; sleep(3); //如果不加锁，threadB输出会是50和200 b += 50; //加锁后会sleep 3秒后，并为b加上50 threadB才能打印 pthread_mutex_unlock(&lock); printf("thread A released the lock! "); a -= 50; } void * threadC() { sleep(1); while(pthread_mutex_trylock(&lock) == EBUSY) //轮询直到获得锁 { printf("thread C is trying to get lock! "); usleep(100000); } printf("thread C got the lock! "); a = 1000; b = 2000; pthread_mutex_unlock(&lock); printf("thread C released the lock! "); } void * threadB() { sleep(2); //让threadA能先执行 pthread_mutex_lock(&lock); printf("thread B got the lock! a=%d b=%d ", a, b); pthread_mutex_unlock(&lock); printf("thread B released the lock! ", a, b); } int main() { pthread_t tida, tidb, tidc; pthread_mutex_init(&lock, NULL); pthread_create(&tida, NULL, threadA, NULL); pthread_create(&tidb, NULL, threadB, NULL); pthread_create(&tidc, NULL, threadC, NULL); pthread_join(tida, NULL); pthread_join(tidb, NULL); pthread_join(tidc, NULL); return 0; } 时间： 2014-01-20