嵌入式操作系统内核原理和开发（互斥量）

作者：网络转载发布时间：[ 2012/9/18 10:19:11 ] 推荐标签：

　　和之前的信号量释放相比，互斥量的释放要复杂一切，关键在于修改优先级的问题。我们来梳理一下，

　　（1）判断参数合法性；

　　（2）判断线程是否为互斥量的占有线程，不是则返回；

　　（3）判断等待队列是否为空，为空的话则返回；

　　（4）判断占有任务的优先级有没有发生变化，如果有则需要重新修改优先级，重新加入调度队列中；

　　（5）选择下一个可以调度的线程；

　　（6）函数返回。

　　说了这么些，剩下后一个删除互斥量了，大家再接再厉，一起去学习。

RAW_U16 raw_mutex_delete(RAW_MUTEX *mutex_ptr)
{
   LIST *block_list_head;

   RAW_TASK_OBJ *mutex_occupy;

   RAW_SR_ALLOC();

   #if (RAW_MUTEX_FUNCTION_CHECK > 0)

   if (mutex_ptr == 0) {
    return RAW_NULL_OBJECT;
   }

   #endif

   block_list_head = &mutex_ptr->common_block_obj.block_list;

   RAW_CRITICAL_ENTER();

   mutex_occupy = mutex_ptr->occupy;
   /*if mutex is occupied and occupy priority is not the original priority*/
   if ((mutex_occupy) && (mutex_occupy->priority != mutex_ptr->occupy_original_priority)) {
    switch (mutex_occupy->task_state) {
     case RAW_RDY:
      /*remove from the ready list*/
      remove_ready_list(&raw_ready_queue， mutex_ptr->occupy);
      /*raise the occupy task priority*/
      mutex_occupy->priority = mutex_ptr->occupy_original_priority;
      /*readd to the ready list head*/
      add_ready_list_end(&raw_ready_queue， mutex_ptr->occupy);
      break;

     case RAW_DLY:
     case RAW_SUSPENDED:
     case RAW_DLY_SUSPENDED:
      /*occupy task is not on any list， so just change the priority*/
      mutex_occupy->priority = mutex_ptr->occupy_original_priority;
      break;

     case RAW_PEND:
     case RAW_PEND_TIMEOUT:
     case RAW_PEND_SUSPENDED:
     case RAW_PEND_TIMEOUT_SUSPENDED:
      /*occupy task is on the block list so change the priority on the block list*/
      mutex_occupy->priority = mutex_ptr->occupy_original_priority;
      change_pend_list_priority(mutex_occupy);

      break;

     default:
      RAW_CRITICAL_EXIT();
      return RAW_STATE_UNKNOWN;
    }
   }


   /*All task blocked on this queue is waken up*/
   while (!is_list_empty(block_list_head)) {
    delete_pend_obj(list_entry(block_list_head->next， RAW_TASK_OBJ， task_list));
   }

   RAW_CRITICAL_EXIT();

   raw_sched();

   return RAW_SUCCESS;
}