Mutex.ReleaseMutex Method

Releases the Mutex once.

Namespace:  System.Threading
Assemblies:   mscorlib (in mscorlib.dll)
  System.Threading (in System.Threading.dll)

member ReleaseMutex : unit -> unit

ExceptionCondition
ApplicationException

The calling thread does not own the mutex.

Whenever a thread acquires a mutex (for example, by calling its WaitOne method), it must subsequently call ReleaseMutex to relinquish ownership of the mutex and unblock other threads that are trying to gain ownership of the mutex. If the attempt to get ownership of the mutex fails (for example, when a call to the WaitOne method with a millisecondsTimeout or a timeout parameter returns false because the request times out), the thread shouldn't call ReleaseMutex, In this case, the thread should also not be allowed to access the resource protected by the mutex, as the following example shows.

No code example is currently available or this language may not be supported.

A thread that owns a mutex can specify the same mutex in repeated wait function calls without blocking its execution. The number of calls is kept by the common language runtime. The thread must call ReleaseMutex the same number of times to release ownership of the mutex.

If a thread terminates while owning a mutex, the mutex is said to be abandoned. The state of the mutex is set to signaled and the next waiting thread gets ownership. If no one owns the mutex, the state of the mutex is signaled. Beginning in version 2.0 of the .NET Framework, an AbandonedMutexException is thrown in the next thread that acquires the mutex. Prior to version 2.0 of the .NET Framework, no exception was thrown.

Caution noteCaution

An abandoned mutex often indicates a serious error in the code. When a thread exits without releasing the mutex, the data structures protected by the mutex might not be in a consistent state. The next thread to request ownership of the mutex can handle this exception and proceed, if the integrity of the data structures can be verified.

In the case of a system-wide mutex, an abandoned mutex might indicate that an application has been terminated abruptly (for example, by using Windows Task Manager).

The following example shows how a local Mutex object is used to synchronize access to a protected resource. The thread that creates the mutex does not own it initially. The ReleaseMutex method is used to release the mutex when it is no longer needed.

No code example is currently available or this language may not be supported.

.NET Framework

Supported in: 4.6, 4.5, 4, 3.5, 3.0, 2.0, 1.1

.NET Framework Client Profile

Supported in: 4, 3.5 SP1

XNA Framework

Supported in: 3.0, 2.0, 1.0

Portable Class Library

Supported in: Portable Class Library

Supported in: Windows Phone 8.1

Supported in: Windows Phone Silverlight 8.1

Supported in: Windows Phone Silverlight 8
Was this page helpful?
(1500 characters remaining)
Thank you for your feedback
Show:
© 2015 Microsoft