shared memory in DLLs?

[X PaYnE X]

I'm trying to share a variable across multiple processes/threads, and make it so that if one process updates the value, all the other processes 'get' the new value.

I read that I could/should use mutex's/semaphores/interlocked* funcs/critical sections/events/file mappings, but I wasnt sure which or why. Heres the code Im using atm, is this a safe method of doing it?

Thanks in advance for any help.

#include <windows.h>
#include <tchar.h>

#pragma data_seg("SHARED")

int nSharedCount;

#pragma data_seg()

#pragma comment(linker, "/section:SHARED,RWS")

BOOL APIENTRY DllMain(HMODULE hModule, DWORD dwReason, LPVOID lpReserved)
{
	switch (dwReason) 
	{ 
		case DLL_PROCESS_ATTACH:
		{
			
		}
		break; 

		case DLL_PROCESS_DETACH:
		{

		}
		break; 
	}
}

void GetCount()
{
	return nSharedCount;
}

void SetCount(int nCount)
{
	nSharedCount = nCount;
}

[Ken Fitlike]

Using Thread Local Storage in a Dynamic-Link Library may be of some interest.