mutex的使用

最新推荐文章于 2024-07-17 15:58:20 发布

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最新推荐文章于 2024-07-17 15:58:20 发布

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文章标签：数据库

原文链接：http://www.cnblogs.com/mikewolf2009/archive/2009/11/21/1607552.html

本文介绍了一个使用Mutex（互斥量）进行进程间同步的例子。通过创建互斥量并利用其在多个线程中保护对共享资源（如数据库写操作）的访问，确保了线程安全。演示了如何创建、等待、释放Mutex。

mutex的使用

类似于临界区，但是可以在进程间同步。

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

#define THREADCOUNT 2

HANDLE ghMutex;

DWORD WINAPI WriteToDatabase( LPVOID );

void main()
{
    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;
    }

    // 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;
        }
    }

    // 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);
}

DWORD WINAPI WriteToDatabase( LPVOID 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;
}