在函数和子函数中调用相同的临界区

Question

我是一名支持工程师，在失败进程的转储中，我看到有一些锁。

使用 Windbg（Visual Studio 无法正确处理调用堆栈）我发现一个函数 (ClassName::F()) 正在恢复。该函数使用一个临界区并调用一个子函数（ClassName::f_sub()），子函数调用相同的临界区，简而言之：

int ClassName::f_sub(){
  EnterCriticalSection(&m_cs);
  ...
  LeaveCriticalSection(&m_cs);
  return ...;
}

int ClassName::F() {
  EnterCriticalSection(&m_cs);
  ...
  int temp = f_sub();
  ...
  LeaveCriticalSection(&m_cs);
  return ...;
}

每次都使用相同的临界区 m_cs（ClassName 的属性）。

在我看来，这使得以下顺序成为可能：

Thread 1 : F()     : Enter the critical section. (Thread 1 is in)
Thread 1 : f_sub() : Enter the critical section. (Thread 1 is in)
Thread 1 : f_sub() : Leave the critical section. (Thread 1 is out)
Thread 2 : F()     : Enter the critical section. (Thread 2 is in) 

=> WRONG! Thread 2 should be forced to wait for Thread 1 leaving the critical section via F().

我的分析是否正确，这是否意味着建议对主函数和子函数使用不同的临界区？

Answer 1

Is my analysis correct and does this mean that it's advised to have different critical sections for main and sub functions?

来自 Microsoft Docs（强调我的）：

After a thread has ownership of a critical section, it can make additional calls to EnterCriticalSection or TryEnterCriticalSection without blocking its execution. This prevents a thread from deadlocking itself while waiting for a critical section that it already owns. The thread enters the critical section each time EnterCriticalSection and TryEnterCriticalSection succeed. A thread must call LeaveCriticalSection once for each time that it entered the critical section.

所以不，你描述的事情不应该发生。多次进入临界区是完全没问题的，离开临界区的次数也一样。

在函数和子函数中调用相同的临界区

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