MSDN上的Mutex代码及其执行结果

MSDN上的Mutex代码及其执行结果

#include <windows.h>
#include <stdio.h>

#define THREADCOUNT 2

HANDLE ghMutex; 

DWORD WINAPI WriteToDatabase( LPVOID );

int main( void )
{
    HANDLE aThread[THREADCOUNT];
    DWORD ThreadID;
    int i;

    // Create a mutex with no initial owner

    ghMutex = CreateMutex( 
        NULL,              // default security attributes
        FALSE,             // initially not owned
        NULL);             // unnamed mutex

    if (ghMutex == NULL) 
    {
        printf("CreateMutex error: %d\n", GetLastError());
        return 1;
    }

    // Create worker threads

    for( i=0; i < THREADCOUNT; i++ )
    {
        aThread[i] = CreateThread( 
                     NULL,       // default security attributes
                     0,          // default stack size
                     (LPTHREAD_START_ROUTINE) WriteToDatabase, 
                     NULL,       // no thread function arguments
                     0,          // default creation flags
                     &ThreadID); // receive thread identifier

        if( aThread[i] == NULL )
        {
            printf("CreateThread error: %d\n", GetLastError());
            return 1;
        }
    }

    // Wait for all threads to terminate

    WaitForMultipleObjects(THREADCOUNT, aThread, TRUE, INFINITE);

    // Close thread and mutex handles

    for( i=0; i < THREADCOUNT; i++ )
        CloseHandle(aThread[i]);

    CloseHandle(ghMutex);

    return 0;
}

DWORD WINAPI WriteToDatabase( LPVOID lpParam )
{ 
    // lpParam not used in this example
    UNREFERENCED_PARAMETER(lpParam);

    DWORD dwCount=0, dwWaitResult; 

    // Request ownership of mutex.

    while( dwCount < 20 )
    { 
        dwWaitResult = WaitForSingleObject( 
            ghMutex,    // handle to mutex
            INFINITE);  // no time-out interval
 
        switch (dwWaitResult) 
        {
            // The thread got ownership of the mutex
            case WAIT_OBJECT_0: 
                __try { 
                    // TODO: Write to the database
                    printf("Thread %d writing to database...\n", 
                            GetCurrentThreadId());
                    dwCount++;
                } 

                __finally { 
                    // Release ownership of the mutex object
                    if (! ReleaseMutex(ghMutex)) 
                    { 
                        // Handle error.
                    } 
                } 
                break; 

            // The thread got ownership of an abandoned mutex
            // The database is in an indeterminate state
            case WAIT_ABANDONED: 
                return FALSE; 
        }
    }
    return TRUE; 
}

Thread 736 writing to database...
Thread 736 writing to database...
Thread 736 writing to database...
Thread 736 writing to database...
Thread 736 writing to database...
Thread 736 writing to database...
Thread 736 writing to database...
Thread 736 writing to database...
Thread 736 writing to database...
Thread 736 writing to database...
Thread 2504 writing to database...
Thread 736 writing to database...
Thread 2504 writing to database...
Thread 736 writing to database...
Thread 2504 writing to database...
Thread 736 writing to database...
Thread 2504 writing to database...
Thread 736 writing to database...
Thread 2504 writing to database...
Thread 736 writing to database...
Thread 2504 writing to database...
Thread 736 writing to database...
Thread 2504 writing to database...
Thread 736 writing to database...
Thread 2504 writing to database...
Thread 736 writing to database...
Thread 2504 writing to database...
Thread 736 writing to database...
Thread 2504 writing to database...
Thread 736 writing to database...
Thread 2504 writing to database...
Thread 2504 writing to database...
Thread 2504 writing to database...
Thread 2504 writing to database...
Thread 2504 writing to database...
Thread 2504 writing to database...
Thread 2504 writing to database...
Thread 2504 writing to database...
Thread 2504 writing to database...
Thread 2504 writing to database...
请按任意键继续. . .

dwCount 为 20，每个线程执行20次。