thread_18

/*例子：下面第二次加锁时将出现死锁，如果改为PTHREAD_MUTEX_ERRORCHECK_NP类型，第二次加锁将会返回非零值，不会出现死锁。*/
#include <stdlib.h>
#include <pthread.h>
#include <stdio.h>
#include <sched.h>
#include <sched.h>
void *consumer1(void *p)
{

          printf("<<<(%u),%d\n", (unsigned)pthread_self(),1);

}
 void *consumer2(void *p)
 {

             printf("<<<(%u),%d\n", (unsigned)pthread_self(), 2);

 }
int main(int argc, char *argv[])
 {pthread_mutex_t mu ;
          pthread_t  t1, t2, t3;
          int ret;
         pthread_mutexattr_t mutexattr;
        pthread_mutexattr_init(&mutexattr);
         pthread_mutexattr_settype(&mutexattr, PTHREAD_MUTEX_ERRORCHECK_NP);

        pthread_mutex_init(&mu, &mutexattr);
        if(!pthread_mutex_lock(&mu))
                printf("get mutex (mian)\n");
         if(!pthread_mutex_lock(&mu))
                  printf("get mutex (main)\n");
         ret = pthread_create(&t1, NULL, consumer1, NULL);
         ret = pthread_create(&t2, NULL, consumer2,NULL);
          if(ret != 0)
          {
                  printf("create failed,%d\n", ret);
                 exit(1);
          }
          sleep(2);
          printf("main returned\n");
       return 0;
  }
/*注意：
PTHREAD_MUTEX_TIMED_NP类型的锁，一个线程加的锁可以被另一个线程解锁，也可以解除未被锁定的锁，不会返回错误。
PTHREAD_MUTEX_ERRORCHECK_NP类型的，加锁和解锁要同一个线程，如果某个线程尝试解除锁定的互斥锁不是由该线程锁定或者未锁定，则将返回错误。*/