信号量使用

在一个文件中释放信号量，怎么在另外一个文件获取呢？

发布于 2021-10-22 09:11:37 浏览：573 订阅该版

recan 认证专家 2021-10-22

公众号【架构师李肯】主理人，每周赠送10本IT书籍，正在挑战100+最佳答案，有疑难问题请邀请我回答@_@

吕蛋蛋 2021-10-22

这家伙很懒，什么也没写！

吕蛋蛋 2021-10-22

这家伙很懒，什么也没写！

static void rt_thread_entry1(void *parameter)
{
      while(1)
      {
          /* 线程 1 获取到互斥量后，先后对 number1、number2 进行加 1 操作，然后释放互斥量 */
          rt_mutex_take(dynamic_mutex, RT_WAITING_FOREVER);
          number1++;
          rt_thread_mdelay(10);
          number2++;
          rt_mutex_release(dynamic_mutex);
       }
}

ALIGN(RT_ALIGN_SIZE)
static char thread2_stack[1024];
static struct rt_thread thread2;
static void rt_thread_entry2(void *parameter)
{
      while(1)
      {
          /* 线程 2 获取到互斥量后，检查 number1、number2 的值是否相同，相同则表示 mutex 起到了锁的作用 */
          rt_mutex_take(dynamic_mutex, RT_WAITING_FOREVER);
          if(number1 != number2)
          {
            rt_kprintf("not protect.number1 = %d, mumber2 = %d \n",number1 ,number2);
          }
          else
          {
            rt_kprintf("mutex protect ,number1 = mumber2 is %d\n",number1);
          }

number1++;
           number2++;
           rt_mutex_release(dynamic_mutex);

if(number1>=50)
              return;
      }
}

就像这个互斥量代码，两个线程都对number进行了自增操作，为什么打印的结果还是顺序的呢，不应该是只打印奇数嘛？

recan 2021-10-22

公众号【架构师李肯】主理人，每周赠送10本IT书籍，正在挑战100+最佳答案，有疑难问题请邀请我回答@_@

吕蛋蛋 2021-10-22

这家伙很懒，什么也没写！

recan 2021-10-22

公众号【架构师李肯】主理人，每周赠送10本IT书籍，正在挑战100+最佳答案，有疑难问题请邀请我回答@_@

@吕蛋蛋 这个代码我也从[官方示例代码](https://docs.rt-thread.org/#/rt-thread-version/rt-thread-standard/programming-manual/ipc1/ipc1?id=%e4%ba%92%e6%96%a5%e9%87%8f)中拉取了，在qemu的模拟环境下跑了一下。
发现结果跟文档提及的有出入，后面仔细分析了下，跟thread1/2的线程优先级有关。
你理解的，理论上应该全部打印出奇数的值，而不应该打印出偶数的，
那么你的前提是thread1/2是交替调度运行的，
即1-》2-》1-》2-》1-》...这样，但实际是可能不是这样的；
你可以像这样加下调试：
![image.png](https://oss-club.rt-thread.org/uploads/20211022/f677605ee50553e1f1770b4bebfd17a4.png.webp)
观察结果：
```c
msh />mutex_sample
1111111111 get mutex ...
msh />2222222222 get mutex ...
mutex protect ,number1 = mumber2 is 1
1111111111 get mutex ...
2222222222 get mutex ...
mutex protect ,number1 = mumber2 is 3
2222222222 get mutex ...
mutex protect ,number1 = mumber2 is 4
2222222222 get mutex ...
mutex protect ,number1 = mumber2 is 5
1111111111 get mutex ...
2222222222 get mutex ...
mutex protect ,number1 = mumber2 is 7
2222222222 get mutex ...
mutex protect ,number1 = mumber2 is 8
2222222222 get mutex ...
mutex protect ,number1 = mumber2 is 9
1111111111 get mutex ...
2222222222 get mutex ...
mutex protect ,number1 = mumber2 is 11
2222222222 get mutex ...
mutex protect ,number1 = mumber2 is 12
2222222222 get mutex ...
mutex protect ,number1 = mumber2 is 13
2222222222 get mutex ...
mutex protect ,number1 = mumber2 is 14
2222222222 get mutex ...
mutex protect ,number1 = mumber2 is 15
2222222222 get mutex ...
mutex protect ,number1 = mumber2 is 16
2222222222 get mutex ...
mutex protect ,number1 = mumber2 is 17
2222222222 get mutex ...
mutex protect ,number1 = mumber2 is 18
2222222222 get mutex ...
mutex protect ,number1 = mumber2 is 19
2222222222 get mutex ...
mutex protect ,number1 = mumber2 is 20
2222222222 get mutex ...
mutex protect ,number1 = mumber2 is 21
2222222222 get mutex ...
mutex protect ,number1 = mumber2 is 22
2222222222 get mutex ...
mutex protect ,number1 = mumber2 is 23
2222222222 get mutex ...
mutex protect ,number1 = mumber2 is 24
2222222222 get mutex ...
mutex protect ,number1 = mumber2 is 25
2222222222 get mutex ...
mutex protect ,number1 = mumber2 is 26
2222222222 get mutex ...
mutex protect ,number1 = mumber2 is 27
2222222222 get mutex ...
mutex protect ,number1 = mumber2 is 28
2222222222 get mutex ...
mutex protect ,number1 = mumber2 is 29
2222222222 get mutex ...
mutex protect ,number1 = mumber2 is 30
2222222222 get mutex ...
mutex protect ,number1 = mumber2 is 31
2222222222 get mutex ...
mutex protect ,number1 = mumber2 is 32
2222222222 get mutex ...
mutex protect ,number1 = mumber2 is 33
2222222222 get mutex ...
mutex protect ,number1 = mumber2 is 34
1111111111 get mutex ...
2222222222 get mutex ...
mutex protect ,number1 = mumber2 is 36
1111111111 get mutex ...
2222222222 get mutex ...
mutex protect ,number1 = mumber2 is 38
1111111111 get mutex ...
2222222222 get mutex ...
mutex protect ,number1 = mumber2 is 40
1111111111 get mutex ...
2222222222 get mutex ...
mutex protect ,number1 = mumber2 is 42
1111111111 get mutex ...
2222222222 get mutex ...
mutex protect ,number1 = mumber2 is 44
1111111111 get mutex ...
2222222222 get mutex ...
mutex protect ,number1 = mumber2 is 46
1111111111 get mutex ...
2222222222 get mutex ...
mutex protect ,number1 = mumber2 is 48
1111111111 get mutex ...
2222222222 get mutex ...
mutex protect ,number1 = mumber2 is 50
1111111111 get mutex ...
1111111111 get mutex ...
1111111111 get mutex ...
1111111111 get mutex ...
1111111111 get mutex ...
1111111111 get mutex ...
1111111111 get mutex ...
1111111111 get mutex ...
1111111111 get mutex ...
1111111111 get mutex ...
1111111111 get mutex ...
```
你会发现，并不是thread1/2交替运行，这就导致打印的结果不全是奇数。