Using Critical Section Objects

The following example shows how a thread initializes, enters, and releases a critical section. It uses the InitializeCriticalSectionAndSpinCount, EnterCriticalSection, LeaveCriticalSection, and DeleteCriticalSection functions.

Warning

Deadlock risk: If a thread must acquire multiple critical sections, always acquire them in a consistent, documented order across all threads. Acquiring locks in different orders from different threads is the most common cause of deadlocks. Also note that EnterCriticalSection blocks indefinitely — use TryEnterCriticalSection for non-blocking acquisition attempts, and implement a bounded retry loop with a deadline if you need timed lock acquisition.

Note

Modern C++ alternative: For new code, consider using std::mutex with std::lock_guard or std::scoped_lock (C++17), which provide RAII-based lock management that ensures release even when exceptions are thrown. For read-heavy workloads, consider Slim Reader/Writer (SRW) Locks or std::shared_mutex.

// Global variable
CRITICAL_SECTION CriticalSection; 

int main( void )
{
    ...

    // Initialize the critical section one time only.
    if (!InitializeCriticalSectionAndSpinCount(&CriticalSection, 
        0x00000400) ) 
        return;
    ...

    // Release resources used by the critical section object.
    DeleteCriticalSection(&CriticalSection);
}

DWORD WINAPI ThreadProc( LPVOID lpParameter )
{
    ...

    // Request ownership of the critical section.
    EnterCriticalSection(&CriticalSection); 

    // Access the shared resource.

    // Release ownership of the critical section.
    LeaveCriticalSection(&CriticalSection);

    ...
return 1;
}