LeaveCriticalSection function (synchapi.h)

Releases ownership of the specified critical section object.


void LeaveCriticalSection(
  [in, out] LPCRITICAL_SECTION lpCriticalSection


[in, out] lpCriticalSection

A pointer to the critical section object.

Return value



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.

A thread uses the EnterCriticalSection or TryEnterCriticalSection function to acquire ownership of a critical section object. To release its ownership, the thread must call LeaveCriticalSection once for each time that it entered the critical section.

If a thread calls LeaveCriticalSection when it does not have ownership of the specified critical section object, an error occurs that may cause another thread using EnterCriticalSection to wait indefinitely.

LeaveCriticalSection does not access the specified CRITICAL_SECTION structure after the ownership of a critical section object is released.

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.


For an example that uses LeaveCriticalSection, see Using Critical Section Objects.


Requirement Value
Minimum supported client Windows XP [desktop apps | UWP apps]
Minimum supported server Windows Server 2003 [desktop apps | UWP apps]
Target Platform Windows
Header synchapi.h (include Windows.h on Windows Server 2003, Windows Vista, Windows 7, Windows Server 2008 Windows Server 2008 R2)
Library Kernel32.lib
DLL Kernel32.dll

See also

Critical Section Objects





Synchronization Functions


Vertdll APIs available in VBS enclaves