c++ - 嵌套临界区是否有效？

Question

例如，这是否有效？

CRITICAL_SECTION cs;

::InitializeCriticalSection( &cs );

::EnterCriticalSection( &cs );      // First level
::EnterCriticalSection( &cs );        // Second level

/* do some stuff */

::LeaveCriticalSection( &cs );        // Second level
::LeaveCriticalSection( &cs );      // First level

::DeleteCriticalSection( &cs );

显然，我绝不会故意这样做，但如果这是由于函数调用导致调用“第一级”以锁定对象以用于复杂(例如搜索)算法和“第二级”在该对象的访问器函数中被调用？

Answer 1

是的，进入相同的临界区是有效的。来自 the docs :

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.