TryEnterCriticalSection function

Attempts to enter a critical section without blocking. If the call is successful, the calling thread takes ownership of the critical section.


BOOL WINAPI TryEnterCriticalSection(
  _Inout_ LPCRITICAL_SECTION lpCriticalSection


lpCriticalSection [in, out]

A pointer to the critical section object.

Return value

If the critical section is successfully entered or the current thread already owns the critical section, the return value is nonzero.

If another thread already owns the critical section, the return value is zero.


The threads of a single process can use a critical section object for mutual-exclusion synchronization. The process is responsible for allocating the memory used by a critical section object, which it can do by declaring a variable of type CRITICAL_SECTION. Before using a critical section, some thread of the process must call the InitializeCriticalSection or InitializeCriticalSectionAndSpinCount function to initialize the object.

To enable mutually exclusive use of a shared resource, each thread calls the EnterCriticalSection or TryEnterCriticalSection function to request ownership of the critical section before executing any section of code that uses the protected resource. The difference is that TryEnterCriticalSection returns immediately, regardless of whether it obtained ownership of the critical section, while EnterCriticalSection blocks until the thread can take ownership of the critical section. When it has finished executing the protected code, the thread uses the LeaveCriticalSection function to relinquish ownership, enabling another thread to become the owner and gain access to the protected resource. The thread must call LeaveCriticalSection once for each time that it entered the critical section.

Any thread of the process can use the DeleteCriticalSection function to release the system resources that were allocated when the critical section object was initialized. After this function has been called, the critical section object can no longer be used for synchronization.

If a thread terminates while it has ownership of a critical section, the state of the critical section is undefined.

To compile an application that uses this function, define _WIN32_WINNT as 0x0400 or later. For more information, see Using the Windows Headers.


Minimum supported client

Windows XP [desktop apps | Windows Store apps]

Minimum supported server

Windows Server 2003 [desktop apps | Windows Store apps]

Minimum supported phone

Windows Phone 8


WinBase.h on Windows XP, Windows Server 2003, Windows Vista, Windows 7, Windows Server 2008 and Windows Server 2008 R2 (include Windows.h);
Synchapi.h on Windows 8 and Windows Server 2012





See also

Critical Section Objects
Synchronization Functions