mutex.c

本程序主要用于说明阅读者写入者问题中的资源互斥访问的调动策略

/*
 * Mutex.c
 *
 * Sample code for "Multithreading Applications in Win32"
 * This sample is discussed in Chapter 4.
 *
 * Graphically demonstrates the problem of the
 * ReaderAndWriter.
 *
 * This version uses mutexes with WaitForSingleObject(),
 * which can cause deadlock, and WaitForMultipleObjects(),
 * which always works properly.
 */

#define WIN32_LEAN_AND_MEAN
#include <stdio.h>
#include <stdlib.h>
#include <windows.h>
#include <time.h>
#include "MtVerify.h"
#include "ReaderAndWriter.h"


int PASCAL WinMain(HINSTANCE, HINSTANCE, LPSTR, int);
BOOL InitApplication(HINSTANCE);
BOOL InitInstance(HINSTANCE, int);

extern HWND   	hWndMain;			// Main Window Handle                             


#define P_DELAY	 rand()/25*10


int Readercount;                       //the number of reader
int readerstate[CCounter];             //the state of reader
int writerstate[CCounter];             //the state of writer
int resourcestate[CCounter];           //the state of resource
CRITICAL_SECTION  RP_Write;            //the variable used to identify the Critical Section
HANDLE count;                          //the resouce used to define the readcount 
#undef PostMessage
#define PostMessage SendMessage

DWORD WINAPI ReaderThread(LPVOID pVoid)
{   int ReaderNum = (int) pVoid;  // get the number of thread(reader)          
    DWORD result;
    //Randomize the random number generator
	srand( (unsigned)time( NULL ) * (ReaderNum + 1) );
    readerstate[ReaderNum] = resting;        //reader is resting
    Sleep(P_DELAY);
	for(;;)
	{// Wait until resources are available
		readerstate[ReaderNum] = waiting;    //reader is waiting
		PostMessage(hWndMain, WM_FORCE_REPAINT,0 ,0);
		result=WaitForSingleObject(count, INFINITE);  //get the resource of count
		if(result==WAIT_OBJECT_0)
			Readercount+=1;
		if(Readercount==1)
			EnterCriticalSection(&RP_Write);  //get the critical section
		MTVERIFY(ReleaseMutex(count));        // release the resource of count
		resourcestate[ReaderNum] = read;
		readerstate[ReaderNum] = reading;     //the reader is reading
		PostMessage(hWndMain, WM_FORCE_REPAINT,0 ,0);
 		Sleep(P_DELAY/4);
		
		result=WaitForSingleObject(count, INFINITE); //get the resource of count
		if(result==WAIT_OBJECT_0)
			Readercount-=1;
		if(Readercount==0)
			LeaveCriticalSection(&RP_Write);     //leave the cristical section
		MTVERIFY(ReleaseMutex(count));           //release the resource of count
		readerstate[ReaderNum] = resting;        //the reader is reading 
		resourcestate[ReaderNum] = UNUSED;
		PostMessage(hWndMain, WM_FORCE_REPAINT,0 ,0);
        Sleep(P_DELAY);
	}
	return 0;
}
DWORD WINAPI WriterThread(LPVOID pVoid)
{  int writerNum = (int)pVoid;   // get the nunber of thread(writer)
	//Randomize the random number generator
	srand( (unsigned)time( NULL ) * (writerNum + 1) );
	writerstate[writerNum] = resting;  //the writer id resting
	Sleep(P_DELAY);
	for(;;)
	{ // Wait until resources are available
		writerstate[writerNum] = waiting;   //the writer is waiting
		PostMessage(hWndMain, WM_FORCE_REPAINT,0 ,0);
    	EnterCriticalSection(&RP_Write);   // enter the critical section
		writerstate[writerNum] = writing;  // the writer is writing
		resourcestate[writerNum] = write;
		PostMessage(hWndMain, WM_FORCE_REPAINT,0 ,0);
		Sleep(P_DELAY/4);
		LeaveCriticalSection(&RP_Write);   //leave the critical section
		writerstate[writerNum] = resting;  // the writer is resting
		resourcestate[writerNum] = UNUSED;
		PostMessage(hWndMain, WM_FORCE_REPAINT,0 ,0);
		Sleep(P_DELAY);
	}
	return 0;
}

int ReaderAndWriter(void)
{
	HANDLE hThread[CCounter];
	HANDLE hThread1[CCounter];
	DWORD dwThreadId;
	int i;
	Readercount = 0;
	resourcestate[CCounter] = UNUSED;
	count = CreateMutex(NULL, FALSE, NULL);
    MTVERIFY(count != NULL);
	InitializeCriticalSection(&RP_Write);  //initialize the critical section
  for (i=0; i < CCounter; i++)
	{//inlitialize the reader and writer state
	  readerstate[i] = resting;  
	  writerstate[i] = resting;
	}

	for (i = 0; i < CCounter; i++)
	{   //creat the reader and writer thread
		MTVERIFY( hThread[i] = CreateThread(NULL, 0, ReaderThread, (LPVOID) i, 0, &dwThreadId ));
        MTVERIFY( hThread1[i] = CreateThread(NULL, 0, WriterThread, (LPVOID) i, 0, &dwThreadId ));
    }
	return 0;
}