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多线程的那点儿事(之避免死锁)

11-12-05

【 声明:版权所有,欢迎转载,请勿用于商业用途。 联系信箱:feixiaoxing @163.com】预防死锁的注意事项:(1)在编写多线程程序之前,首先编写正确的程序,然后再移植到多线程(2)时刻检查自己写的程序有没...

 

【 声明:版权所有,欢迎转载,请勿用于商业用途。  联系信箱:feixiaoxing @163.com】

 

 

预防死锁的注意事项:

 

(1)在编写多线程程序之前,首先编写正确的程序,然后再移植到多线程

 

(2)时刻检查自己写的程序有没有在跳出时忘记释放锁

 

(3)如果自己的模块可能重复使用一个锁,建议使用嵌套锁

 

(4)对于某些锁代码,不要临时重新编写,建议使用库里面的锁,或者自己曾经编写的锁

 

(5)如果某项业务需要获取多个锁,必须保证锁的按某种顺序获取,否则必定死锁

 

(6)编写简单的测试用例,验证有没有死锁

 

(7)编写验证死锁的程序,从源头避免死锁

 

 

 

 

    首先,定义基本的数据结构和宏,

 

 

typedef struct _LOCK_INFO 

    char lockName[32]; 

    HANDLE hLock; 

}LOCK_INFO: 

 

typedef struct _THREAD_LOCK 

    int threadId; 

    LOCK_INFO* pLockInfo[32]; 

}THREAD_LOCK; 

 

#define CRITICAL_SECTION_TYPE 1  

#define MUTEX_LOCK_TYPE       2  

#define SEMAPHORE_LOCK_TYPE   3  

#define NORMAL_LOCK_TYPE      4  

 

#define WaitForSingleObject(a, b) \  

        WaitForSingleObject_stub((void*)a, NORMAL_LOCK_TYPE) 

 

#define EnterCriticalSection(a) \  

        WaitForSingleObject_stub((void*)a, CRITICAL_SECTION_TYPE) 

 

#define ReleaseMutex(a) \  

        ReleaseLock_stub((void*)a, MUTEX_LOCK_TYPE)) 

 

#define ReleaseSemaphore(a, b, c) \  

        ReleaseLock_stub((void*)a, SEMAPHORE_LOCK_TYPE)) 

 

#define LeaveCriticalSection(a) \  

        ReleaseLock_stub((void*)a, CRITICAL_SECTION_TYPE)) 

typedef struct _LOCK_INFO

{

    char lockName[32];

    HANDLE hLock;

}LOCK_INFO:

 

typedef struct _THREAD_LOCK

{

    int threadId;

    LOCK_INFO* pLockInfo[32];

}THREAD_LOCK;

 

#define CRITICAL_SECTION_TYPE 1

#define MUTEX_LOCK_TYPE       2

#define SEMAPHORE_LOCK_TYPE   3

#define NORMAL_LOCK_TYPE      4

 

#define WaitForSingleObject(a, b) \

        WaitForSingleObject_stub((void*)a, NORMAL_LOCK_TYPE)

 

#define EnterCriticalSection(a) \

        WaitForSingleObject_stub((void*)a, CRITICAL_SECTION_TYPE)

 

#define ReleaseMutex(a) \

        ReleaseLock_stub((void*)a, MUTEX_LOCK_TYPE))

 

#define ReleaseSemaphore(a, b, c) \

        ReleaseLock_stub((void*)a, SEMAPHORE_LOCK_TYPE))

 

#define LeaveCriticalSection(a) \

        ReleaseLock_stub((void*)a, CRITICAL_SECTION_TYPE))    然后,改写锁的申请函数,

 

 

void WaitForSingleObject_stub(void* hLock, int type) 

    /* step 1 */ 

    WaitForSingleObject(hDbgLock); 

    /* check if lock loops arounds threads */ 

    ReleaseMutex(hDbgLock); 

 

    /* step 2 */ 

    if(NORMAL_LOCK_TYPE == type) 

        WaitForSingleObject((HANDLE)hLock, INFINITE); 

    else if(CRITICAL_SECTION_TYPE == type) 

        EnterCriticalSection((LPCRITICAL_SECTION)hLock); 

    else 

        assert(0); 

 

    /* step 3 */ 

    WaitForSingleObject(DbgLock); 

    /* add lock to specified threadid list */ 

    ReleaseMutex(hDbgLock); 

void WaitForSingleObject_stub(void* hLock, int type)

{

    /* step 1 */

    WaitForSingleObject(hDbgLock);

    /* check if lock loops arounds threads */

    ReleaseMutex(hDbgLock);

 

    /* step 2 */

    if(NORMAL_LOCK_TYPE == type)

        WaitForSingleObject((HANDLE)hLock, INFINITE);

    else if(CRITICAL_SECTION_TYPE == type)

        EnterCriticalSection((LPCRITICAL_SECTION)hLock);

    else

        assert(0);

 

    /* step 3 */

    WaitForSingleObject(DbgLock);

    /* add lock to specified threadid list */

    ReleaseMutex(hDbgLock);

}    最后,需要改写锁的释放函数。

 

 

void ReleaseLock_stub(void* hLock, int type) 

    /* step 1 */ 

    WaitForSingleObject(hDbgLock); 

    /* remove lock from specified threadid list */ 

    ReleaseMutex(hDbgLock); 

 

    /* step 2 */ 

    if(MUTEX_LOCK_TYPE))== type) 

        ReleaseMutex(HANDLE)hLock); 

    else if(SEMAPHORE_LOCK_TYPE == type)  

        ReleaseSemaphore((HANDLE)hLock, 1, NULL); 

    else if(CRITICAL_SECTION_TYPE == type) 

        LeaveCriticalSection((LPCRITICAL_SECTION)hLock); 

    assert(0); 

void ReleaseLock_stub(void* hLock, int type)

{

    /* step 1 */

    WaitForSingleObject(hDbgLock);

    /* remove lock from specified threadid list */

    ReleaseMutex(hDbgLock);

 

    /* step 2 */

    if(MUTEX_LOCK_TYPE))== type)

        ReleaseMutex(HANDLE)hLock);

    else if(SEMAPHORE_LOCK_TYPE == type)

        ReleaseSemaphore((HANDLE)hLock, 1, NULL);

    else if(CRITICAL_SECTION_TYPE == type)

        LeaveCriticalSection((LPCRITICAL_SECTION)hLock);

    assert(0);

}

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