几个重要的函数：
#include <pthread.h>
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：
int a = 100;
int b = 200;
pthread_mutex_t lock;
void * threadA()
{
pthread_mutex_lock(&lock);
printf("thread A got lock!\n");
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!\n");
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!\n");
usleep(100000);
}
printf("thread C got the lock!\n");
a = 1000;
b = 2000;
pthread_mutex_unlock(&lock);
printf("thread C released the lock!\n");
}
void * threadB()
{
sleep(2); //让threadA能先执行
pthread_mutex_lock(&lock);
printf("thread B got the lock! a=%d b=%d\n", a, b);
pthread_mutex_unlock(&lock);
printf("thread B released the lock!\n", 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;
}
