EnterCriticalSection

A version of this page is also available for

Windows Embedded CE 6.0 R3

4/8/2010

This function waits for ownership of the specified critical section object. The function returns when the calling thread is granted ownership.

Syntax

void EnterCriticalSection(
  LPCRITICAL_SECTION lpCriticalSection
);

Parameters

• lpCriticalSection
  [in] Pointer to the critical section object.

Return Value

None.

Remarks

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 to initialize the object.

To enable mutually exclusive access to a shared resource, each thread calls the EnterCriticalSection function to request ownership of the critical section before executing any section of code that accesses the protected resource. 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 owner and access the protected resource. The thread must call LeaveCriticalSection once for each time that it entered the critical section. The thread enters the critical section each time EnterCriticalSection succeeds.

After a thread has ownership of a critical section, it can make additional calls to EnterCriticalSection without blocking its execution. This prevents a thread from deadlocking itself while waiting for a critical section that it already owns.

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.

If a critical section is deleted while it is still owned, the state of the threads waiting for ownership of the deleted critical section is undefined.

If multiple threads call EnterCriticalSection, and the critical section is currently owned by a different thread, the highest priority thread among the calling threads gets the critical section first after the current thread leaves the critical section. If all the calling threads have the same priority, a first-in, first-out (FIFO) basis is used after the current thread leaves the critical section.

Each object type, such as memory maps, semaphores, events, message queues, mutexes, and watchdog timers, has its own separate namespace. Empty strings, "", are handled as named objects. On Windows desktop-based platforms, synchronization objects all share the same namespace.

Requirements

See Also

Reference

Synchronization Functions
DeleteCriticalSection
InitializeCriticalSection
LeaveCriticalSection