I know, it's already there in MSDN, but it's hard to find. So I am pasting it here to refer to some of my colleagues for better understanding of mutex
Using Mutex Objects
You can use a mutex object to protect a shared resource from simultaneous access by multiple threads or processes. Each thread must wait for ownership of the mutex before it can execute the code that accesses the shared resource. For example, if several threads share access to a database, the threads can use a mutex object to permit only one thread at a time to write to the database.
In the following example, a process uses the CreateMutex function to create a mutex object.
hMutex = CreateMutex(
if (hMutex == NULL)
printf("CreateMutex error: %d\n", GetLastError());
When a thread of this process writes to the database, as in the next example, it first requests ownership of the mutex. If it gets ownership, the thread writes to the database and then releases its ownership.
The example uses structured exception-handling syntax to ensure that the thread properly releases the mutex object. The __finally block of code is executed no matter how the __try block terminates (unless the __try block includes a call to the TerminateThread function). This prevents the mutex object from being abandoned inadvertently.
BOOL FunctionToWriteToDatabase(HANDLE hMutex)
dwWaitResult = WaitForSingleObject(
if (! ReleaseMutex(hMutex))