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WINAPI thread problem

samguddy (6)
Hey there,
I've been working on this project for a long time now and can't seem to find how this is done.

c++ language under windows.

I created 4 threads. Inside one of the threads I want to call another thread funtion. How is this done?? Cause it does not seem to work like other threads.

Thanks so much in advance.

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DWORD WINAPI R1 (LPVOID)
{
      while(TestAndSet(&lock))
          while(lock==true);

	readcount++;
	cout << "R1 in CS." << endl;
	cout << readcount << "Readers in CS." << endl;
	cout << writecount << "Wrtiers in CS." << endl;	
	
           //want to call a thread here. example R#2.
		
               readcount--;
	  lock=false;
			
		return (DWORD) 0;	
	
			}
kbw (9488)
You shouldn't do:
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      while(TestAndSet(&lock))
          while(lock==true);


You can't sych threads with normal variables. You need semaphores (or mutexes).
samguddy (6)
Here is the full source code.All im basicaly trying to do is prevent other threads from running whiles there is one in the critical section.Which seems to be working fine. What I really want to know is how to call one of the threads inside another.

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#include <iostream>
#include <windows.h>
using namespace std;
#define maxthreads 4

DWORD id[maxthreads];
DWORD waiter;
HANDLE threadhandle[maxthreads];

DWORD WINAPI R1 (LPVOID);
DWORD WINAPI R2 (LPVOID);
DWORD WINAPI W1 (LPVOID);
DWORD WINAPI W2 (LPVOID);

int readcount=0,writecount=0,data,perform;


bool lock=false;
 bool TestAndSet(bool *y)
{
	bool rv=lock;
	lock=true;
	return rv;
	}
	
	
DWORD WINAPI R1 (LPVOID)
{
		while(TestAndSet(&lock))
		while(lock==true);

		readcount++;
		cout << "R1 in CS." << endl;
		cout << readcount << "Readers in CS." << endl;
		cout << writecount << "Wrtiers in CS." << endl;	
			readcount--;
			lock=false;
		
			
	
			
		return (DWORD) 0;	
	
			}
			
DWORD WINAPI R2 (LPVOID)
{
	
		while(TestAndSet(&lock))
		while(lock==true);
		readcount++;
		cout << "R2 in CS." << endl;
		cout << readcount << "Readers in CS." << endl;
		cout << writecount << "Wrtiers in CS." << endl;
			
			readcount--;
			lock=false;
	
		return (DWORD) 0;
			}
			
			
DWORD WINAPI W1 (LPVOID)
{

		while(TestAndSet(&lock))
		while(lock==true);
		writecount++;
		cout << "W1 in CS." << endl;
		cout << readcount << "Readers in CS." << endl;
		cout << writecount << "Wrtiers in CS." << endl;	
		for (int s=0;s<=1000;s++)
			{
					perform*=s;
			
				data +=perform;
			}
			writecount--;
			lock=false;
			
	
	return (DWORD) 0;
			}
			
DWORD WINAPI W2 (LPVOID)
{
	
	
		while(TestAndSet(&lock))
		while(lock==true);
		writecount++;
		cout << "W2 in CS." << endl;
		cout << readcount << "Readers in CS." << endl;
		cout << writecount << "Wrtiers in CS." << endl;

			for (int s=0;s<=1000;s++)
			{
				
				perform*=s;
			
				data +=perform;
			}
			
			writecount--;
			lock=false;

	

			return (DWORD) 0;
}
			

			
int main(int argc, char *argv[])
{
	threadhandle[0]=CreateThread(NULL,0,R1,(LPVOID)0,0,&id[0]);
	threadhandle[1]=CreateThread(NULL,0,R2,(LPVOID)0,0,&id[1]);
	threadhandle[2]=CreateThread(NULL,0,W1,(LPVOID)0,0,&id[2]);
	threadhandle[3]=CreateThread(NULL,0,W2,(LPVOID)0,0,&id[3]);
	
			
	
	waiter = WaitForMultipleObjects(maxthreads,threadhandle,TRUE,INFINITE);
			for(int i = 0; i < maxthreads; i++)
    {
        CloseHandle(threadhandle[i]);
    }
	
	}
writetonsharma (1461)
when you change variables between threads use critical section, as you are on windows critical section will be fine.

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// Request ownership of the critical section.
EnterCriticalSection(&CriticalSection); 

    // Access the shared resource.

    // Release ownership of the critical section.
LeaveCriticalSection(&CriticalSection);



see msdn for this.
also, if you just want to increment or decrement variables, you can use
InterlockedIncrement
which will give you atomic operation.
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