问题代码:
1 #include<windows.h>
2 #include<iostream>
3 #include<thread>
4 HANDLE h1;
5 HANDLE h2;
6
7 void CALLBACK test(PVOID a, BOOLEAN b)
8 {
9 std::cout << "This a test function excuted by Thread:" << std::this_thread::get_id()<< std::endl;
10 //std::cout << "Here we try to delete timer in Thread:" << std::this_thread::get_id() << std::endl;
11 if (0 == DeleteTimerQueueTimer(NULL, h1, INVALID_HANDLE_VALUE))
12 {
13 std::cout << "Timer Deleted Failed in Thread:" << std::this_thread::get_id() << std::endl;
14 }
15 std::cout << "Timer Deleted Successfully in Thread:" << std::this_thread::get_id() << std::endl;
16
17 }
18 void CALLBACK test1(PVOID l, BOOLEAN t)
19 {
20 std::cout << "This a test1 function excuted by Thread:" << std::this_thread::get_id() << std::endl;
21 }
22
23 int main()
24 {
25
26 std::cout << "******This is a Test for TimeQueueTimer in Windows API******" << std::endl;
27 std::cout << "Main thread is executed by thread: " << std::this_thread::get_id() << std::endl;
28 //test(PVOID(1), TRUE);
29 try
30 {
31 CreateTimerQueueTimer(&h1, NULL, WAITORTIMERCALLBACK(test), NULL, 0, 1000, WT_EXECUTEINTIMERTHREAD);
32 //Sleep(1000);
33
34 CreateTimerQueueTimer(&h2, NULL, WAITORTIMERCALLBACK(test1), NULL, 0, 1000, WT_EXECUTEINTIMERTHREAD);
35
36
37 //CreateTimerQueueTimer(&h1, NULL, [](PVOID lpParameter, BOOLEAN TimerOrWaitFired) {
38 // test(lpParameter, TimerOrWaitFired); // Call your original test function from within the lambda
39 // }, NULL, 0, 1000, WT_EXECUTEINTIMERTHREAD);
40
41 }
42 catch (const std::exception& e)
43 {
44 std::cout << "something error with the timer: " << e.what() << std::endl;
45 }
46
47
48 if (std::cin.get())
49 {
50 if (0 == DeleteTimerQueueTimer(NULL, h2, INVALID_HANDLE_VALUE))
51 {
52 std::cout << "Timer Deleted Failed in Thread:" << std::this_thread::get_id() << std::endl;
53 }
54 std::cout << "Timer Deleted Successfully in Thread:" << std::this_thread::get_id() << std::endl;
55
56 };
57 Sleep(1000);
58
59 return 0;
60 }
Main()函数中test1回调无法执行!
问题分析:
CreateTimerQueueTimer和DeleteTimerQueueTimer 分别负责线程的开启和中止,函数定义如下:
BOOL CreateTimerQueueTimer(
[out] PHANDLE phNewTimer,
[in, optional] HANDLE TimerQueue,
[in] WAITORTIMERCALLBACK Callback,
[in, optional] PVOID Parameter,
[in] DWORD DueTime,
[in] DWORD Period,
[in] ULONG Flags
);
BOOL DeleteTimerQueueTimer(
[in, optional] HANDLE TimerQueue,
[in] HANDLE Timer,
[in, optional] HANDLE CompletionEvent
);
主线程中分别利用CreateTimerQueueTimer开启后台线程调用回调test()和test1(),并在test()调用中结束调用。由于DeleteTimerQueueTimer中CompletionEvent中使用的是INVALID_HANDLE_VALUE,导致线程会等待所有timer线程执行结束,才能返回。而当前执行回调的线程等不到自己结束,陷入死锁。因为CreateTimerQueueTimer的Flag参数使用的是WT_EXECUTEINTIMERTHREAD,导致test1回调和test使用的是同一线程,而test线程已经死锁,所以test1也无法得到执行
解决方案:
- 不应该在回调中调用DeleteTimerQueueTimer中止线程
- 如果必须在回调中中止线程,CompletionEvent应设为NULL,标记当前线程结束后,直接返回0(执行失败),回调执行完,不再继续执行
- CreateTimerQueueTimer使用Flag WT_EXECUTEDEFAULT开启新线程,即使上一个timer线程死锁,第二个线程仍可以执行