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The KeReleaseMutex routine releases a given mutex object, specifying whether the caller is to call one of KeWaitXxx as soon as KeReleaseMutex returns control.
LONG
KeReleaseMutex(
IN PRKMUTEX Mutex,
IN BOOLEAN Wait
);
If the return value is zero, the mutex object was released and attained a state of signaled.
Declared in wdm.h and ntddk.h. Include wdm.h or ntddk.h.
For better performance, use the ExXxxFastMutex routines instead of the KeXxxMutex routines. However, a fast mutex cannot be acquired recursively, as a kernel mutex can.
If the mutex object attains a signaled state, an attempt is made to satisfy a wait for the mutex object.
A mutex object can be released only by the thread currently holding the mutex. If an attempt is made to release a mutex not held by the thread, a bug check occurs. An attempt to release a mutex object whose current state is signaled also causes a bug check to occur.
When a mutex object attains a signaled state, it is removed from the list of mutexes held by that thread. If the thread’s owned mutex list does not contain any more entries, the thread’s original priority is restored.
If the value of the Wait parameter is TRUE, the return to the caller is executed without lowering IRQL or releasing the dispatcher database spin lock. Therefore, the call to KeReleaseMutex must be followed immediately by a call to one of KeWaitXxx.
This allows the caller to release a mutex and wait as one atomic operation, preventing a possibly superfluous context switch. However, a caller cannot wait at raised IRQL nor in an arbitrary thread context for a nonzero interval on a mutex object.
If a mutex is acquired recursively, the holding thread must call KeReleaseMutex as many times as it acquired the mutex to set it to the signaled state.
Callers of KeReleaseMutex must be running at IRQL <= DISPATCH_LEVEL.
ExReleaseFastMutex, ExReleaseFastMutexUnsafe, KeInitializeMutex, KeReadStateMutex, KeWaitForMultipleObjects, KeWaitForMutexObject, KeWaitForSingleObject