PulseEvent Useless?

MSDN上明确写道:“Therefore, PulseEvent is unreliable and should notbe used by new applications. Instead, use condition variables.”,MSDN给的理由是:“A thread waiting on asynchronization object can be momentarily removed from the wait state by akernel-mode APC, and then returned to the wait state after the APC is complete.

然而,在某些scenarios中,PulseEvent还是有用的。例如:我们有一个WinCE上的项目,软件里的一个worker thread1通过串口向硬件发送一个命令后会阻塞等待硬件给出回应(ACK),而另一个worker thread2会接受并处理硬件通过串口发来的各种数据,包括ACK信息。由于thread2处理信息时可能导致ACK处理的滞后,此时thread1的阻塞等待状态可能已经time out,并且可能马上要进入到下一个阻塞等待状态。这种情况下,PulseEvent可以替我们缓解一下ACK错误匹配的问题。

当然,应该注意的是:PulseEvent在上述场合下的作用只是一个缓解,问题的根本解决可能需要重新的设计或不存在一个100%正确的解决方案。但是,这却是一个事实存在,而且很可能不是唯一的。
#include <iostream.h> #include <windows.h> HANDLE hMutex; HANDLE hNotFullEvent; HANDLE hAlphabetEvent,hNumberEvent,hSymbolEvent; const int BufferSize = 15; char Buffer[BufferSize]; int count = 0; int alphabet = 0; int number = 0; int symbol = 0; int head = 0; int tail = 0; /************************************************ /* /* 显示缓冲区情况函数 /* ************************************************/ void showbuffer(char a[15]) { cout<<"缓冲区存储情况为(^为已消费资源):"; for(int i=0;i<15;i++) { cout<<a[i]<<" "; } cout<<endl; } /************************************************ /* /* 生产者进程P1:输入大写字母A /* ************************************************/ UINT ProThreadP1(LPVOID pParam) { for(;;) { for(;;) { WaitForSingleObject(hMutex,INFINITE); if( count == BufferSize ) { ReleaseMutex(hMutex); WaitForSingleObject(hNotFullEvent,INFINITE); continue; } break; } cout<<"生产者进程P1:产生大写字母A"<<endl; Buffer[tail] = 'A'; showbuffer(Buffer); if(tail == 14) tail = 0; else tail++; count++; alphabet++; cout<<"按Enter继续,按q退出程序:"<<endl; char ch; ch = cin.get(); if(ch == 'q' || ch == 'Q') { ReleaseMutex(hMutex); PulseEvent(hAlphabetEvent); exit(0); } ReleaseMutex(hMutex); PulseEvent(hAlphabetEvent); } } /************************************************ /* /* 生产者进程P2:输入数字1 /* ************************************************/ UINT ProThreadP2(LPVOID pParam) { for(;;) { for(;;) { WaitForSingleObject(hMutex,INFINITE); if( count == BufferSize ) { ReleaseMutex(hMutex); WaitForSingleObject(hNotFullEvent,INFINITE); continue; } break; } cout<<"生产者进程P2:产生数字1"<<endl; Buffer[tail] = '1'; showbuffer(Buffer); if(tail == 14) tail = 0; else tail++; count++; number++; cout<<"按Enter继续,按q退出程序:"<<endl; char ch; ch = cin.get(); if(ch == 'q' || ch == 'Q') { ReleaseMutex(hMutex); PulseEvent(hNumberEvent); exit(0); } ReleaseMutex(hMutex); PulseEvent(hNumberEvent); } } /************************************************ /* /* 生产者进程P3:输入符号* /* ************************************************/ UINT ProThreadP3(LPVOID pParam) { for(;;) { for(;;) { WaitForSingleObject(hMutex,INFINITE); if( count == BufferSize ) { ReleaseMutex(hMutex); WaitForSingleObject(hNotFullEvent,INFINITE); continue; } break; } cout<<"生产者进程 p3:产生符号* "<<endl; Buffer[tail] = '*'; showbuffer(Buffer); if(tail == 14) tail = 0; else tail++; count++; symbol++; cout<<"按Enter继续,按q退出程序:"<<endl; char ch; ch = cin.get(); if(ch == 'q' || ch == 'Q') { ReleaseMutex(hMutex); PulseEvent(hSymbolEvent); exit(0); } ReleaseMutex(hMutex); PulseEvent(hSymbolEvent); } } /************************************************ /* /* 消费者进程C1:大写A转成小写a /* ************************************************/ UINT ConThreadC1(LPVOID pParam) { for(;;) { WaitForSingleObject(hMutex,INFINITE); if(alphabet == 0) { ReleaseMutex(hMutex); WaitForSingleObject(hAlphabetEvent,INFINITE); continue; } else { cout<<"消费者进程C1:大写A转成小写a"<<endl; int i; for(i=head;Buffer[i] != 'A';) { if(i == 14) { if(Buffer[i] == 'A') break; i = 0; continue; } i++; } Buffer[i] = 'a'; showbuffer(Buffer); if(i-head>=0) { for(int j=0;j<i-head;j++) { Buffer[i] = Buffer[i-1]; i--; } } else { for(;i>0;i--) { Buffer[i] = Buffer[i-1]; } Buffer[i] = Buffer[BufferSize-1]; for(i=BufferSize-1;i-head>0;i--) { Buffer[i] = Buffer[i-1]; } } Buffer[head] = '^'; if(head == 14) head = 0; else head++; count--; alphabet--; cout<<"按Enter继续,按q退出程序:"<<endl; char ch; ch = cin.get(); if(ch == 'q' || ch == 'Q') { ReleaseMutex(hMutex); PulseEvent(hNotFullEvent); exit(0); } ReleaseMutex(hMutex); PulseEvent(hNotFullEvent); } } } /************************************************ /* /* 消费者进程C2:将数字1转为数字2 /* ************************************************/ UINT ConThreadC2(LPVOID pParam) { for(;;) { WaitForSingleObject(hMutex,INFINITE); if(number == 0) { ReleaseMutex(hMutex); WaitForSingleObject(hNumberEvent,INFINITE); continue; } else { cout<<"消费者进程C2:将数字1转为数字2"<<endl; int i; for(i=head;Buffer[i] != '1';) { if(i == 14) { if(Buffer[i] == '1') break; i = 0; continue; } i++; } Buffer[i] = '2'; showbuffer(Buffer); if(i-head>=0) { for(int j=0;j<i-head;j++) { Buffer[i] = Buffer[i-1]; i--; } } else { for(;i>0;i--) { Buffer[i] = Buffer[i-1]; } Buffer[i] = Buffer[BufferSize-1]; for(i=BufferSize-1;i-head>0;i--) { Buffer[i] = Buffer[i-1]; } } Buffer[head] = '^'; if(head == 14) head = 0; else head++; count--; number--; cout<<"按Enter继续,按q退出程序:"<<endl; char ch; ch = cin.get(); if(ch == 'q' || ch == 'Q') { ReleaseMutex(hMutex); PulseEvent(hNotFullEvent); exit(0); } ReleaseMutex(hMutex); PulseEvent(hNotFullEvent); } } } /************************************************ /* /* 消费者进程C3:将符号*转为符号# /* ************************************************/ UINT ConThreadC3(LPVOID pParam) { for(;;) { WaitForSingleObject(hMutex,INFINITE); if(symbol == 0) { ReleaseMutex(hMutex); WaitForSingleObject(hSymbolEvent,INFINITE); continue; } else { cout<<"消费者进程C3:将符号*转为符号#"<<endl; int i; for(i=head;Buffer[i] != '*';) { if(i == 14) { if(Buffer[i] == '*') break; i = 0; continue; } i++; } Buffer[i] = '#'; showbuffer(Buffer); if(i-head>=0) { for(int j=0;j<i-head;j++) { Buffer[i] = Buffer[i-1]; i--; } } else { for(;i>0;i--) { Buffer[i] = Buffer[i-1]; } Buffer[i] = Buffer[BufferSize-1]; for(i=BufferSize-1;i-head>0;i--) { Buffer[i] = Buffer[i-1]; } } Buffer[head] = '^'; if(head == 14) head = 0; else head++; count--; symbol--; cout<<"按Enter继续,按q退出程序:"<<endl; char ch; ch = cin.get(); if(ch == 'q' || ch == 'Q') { ReleaseMutex(hMutex); PulseEvent(hNotFullEvent); exit(0); } ReleaseMutex(hMutex); PulseEvent(hNotFullEvent); } } } /************************************************ /* /* 消费者进程C4:大写A转成大写B /* ************************************************/ UINT ConThreadC4(LPVOID pParam) { for(;;) { WaitForSingleObject(hMutex,INFINITE); if(alphabet == 0) { ReleaseMutex(hMutex); WaitForSingleObject(hAlphabetEvent,INFINITE); continue; } else { cout<<"消费者进程C4:大写A转成大写B"<<endl; int i; for(i=head;Buffer[i] != 'A';) { if(i == 14) { if(Buffer[i] == 'A') break; i = 0; continue; } i++; } Buffer[i] = 'B'; showbuffer(Buffer); if(i-head>=0) { for(int j=0;j<i-head;j++) { Buffer[i] = Buffer[i-1]; i--; } } else { for(;i>0;i--) { Buffer[i] = Buffer[i-1]; } Buffer[i] = Buffer[BufferSize-1]; for(i=BufferSize-1;i-head>0;i--) { Buffer[i] = Buffer[i-1]; } } Buffer[head] = '^'; if(head == 14) head = 0; else head++; count--; alphabet--; cout<<"按Enter继续,按q退出程序:"<<endl; char ch; ch = cin.get(); if(ch == 'q' || ch == 'Q') { ReleaseMutex(hMutex); PulseEvent(hNotFullEvent); exit(0); } ReleaseMutex(hMutex); PulseEvent(hNotFullEvent); } } } int main() { HANDLE hThreadVector[7]; DWORD ThreadID; hMutex=CreateMutex(NULL,FALSE,NULL); hNotFullEvent=CreateEvent(NULL,TRUE,FALSE,NULL); hThreadVector[0]=CreateThread (NULL, 0,(LPTHREAD_START_ROUTINE) ProThreadP1,NULL, 0, (LPDWORD)&ThreadID); hThreadVector[1]=CreateThread (NULL, 0,(LPTHREAD_START_ROUTINE) ConThreadC3,NULL, 0, (LPDWORD)&ThreadID); hThreadVector[2]=CreateThread (NULL, 0,(LPTHREAD_START_ROUTINE) ProThreadP3,NULL, 0, (LPDWORD)&ThreadID); hThreadVector[3]=CreateThread (NULL, 0,(LPTHREAD_START_ROUTINE) ConThreadC1,NULL, 0, (LPDWORD)&ThreadID); hThreadVector[4]=CreateThread (NULL, 0,(LPTHREAD_START_ROUTINE) ConThreadC2,NULL, 0, (LPDWORD)&ThreadID); hThreadVector[5]=CreateThread (NULL, 0,(LPTHREAD_START_ROUTINE) ProThreadP2,NULL, 0, (LPDWORD)&ThreadID); hThreadVector[6]=CreateThread (NULL, 0,(LPTHREAD_START_ROUTINE) ConThreadC4,NULL, 0, (LPDWORD)&ThreadID); WaitForMultipleObjects(7,hThreadVector,TRUE,INFINITE); return 0; } 根据这个换成精简一点,换成缓冲池为10.三个生产消费,
05-21
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