1.互斥量的概念前面已经提及
2.一个demo
要求 四个线程,每个线程分别输出a b c d,是拼命输出,如何让他们在终端上输出顺序的a b c d
pthread_mutex_t mut[THRNUM];
void * Fun(void *p)
{
int c = 'a' + (int)p;
int i = (int)p;
int next = (i+1)%THRNUM;
while(1)
{
pthread_mutex_lock(mut+i);
write(1, &c, 1);
pthread_mutex_unlock(mut+next);
}
pthread_exit(NULL);
}
int main()
{
pthread_t tid[THRNUM];
int i,err;
for(i = 0 ; i <= THRNUM; i++)
{
pthread_mutex_init(mut+i, NULL);
pthread_mutex_lock(mut+i);
err = pthread_create(tid+i, NULL, Fun, (void *)i);
if(err)
{
fprintf(stderr, "create()%s ", strerror(err));
exit(1);
}
}
pthread_mutex_unlock(mut+0);
alarm(1);
for(i = 0; i <= THRNUM; i++)
{
pthread_join(tid[i], NULL);
}
for(i = 0; i <= THRNUM; i++)
pthread_mutex_destroy(mut+i);
return 0;
}
我们在每创建一个线程的时候,先把其锁住,然后每个线程获取一个锁,再次阻塞,我们在main线程中打开了a的锁,然后a写入完成后,他打开b的锁,b可以运行,然后再打开c的锁,一次类推