多线程的那点儿事（之避免死锁）
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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);
补充：软件开发 , 其他 ,
