Synchronization in a DLL

[VFaul]

I'm writing a DLL that can be accessed by multiple applications. The DLL talks to hardware (through a third-party driver). I need to block all other calls to the DLL while the DLL is talking to the hardware. What is the best synchrounization method - critical section, mutex,...? Also, I think the synchronization object in the DLL needs to be global so it can be accessed by multiple processes. How do I do that? Thanks, VF

[jhwurmbach]

A critical section seems taylor-made for your requirements. No need to worry about where to allocate the synchonisation object: Your routines in the DLL do this before accessing the Hardware.

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Though I speak with the tongues of men and of angels, and have not money, I am become as a sounding brass, or a tinkling cymbal.
George Orwell, "Keep the Aspidistra Flying", Opening words

[Iain Clarke Warrior Programmer]

Critical sections won't work, as you can't operate on the same one across process boundaries. Using the Name part of CreateMutex looks like what you need. Saying that, its going to be very upsetting for program B if it suddenly freezes because program A is doing something. Back to the bad old days of Win 3.x... You may have legitimate need for this, but I would think *very* carefully about which functions you block... Iain.

[DevMentor org]

if you're going to sync threads in the same process than work with critical section, they are the most efficient to share objects in multiple process, it is best to work with a mutex btw, mutex are global object system objects so if you sync on that you will be ok....if you need share data you can work with shared memory, but make sure that the DLL has APIs to both allcate and free the shared memory and the applications calls these API to allocate/free the memory otherwise you're going to have issues with memory leaks. read up on DLLs in MSDN and understand the limitation of passing object across DLL boundaries.

Yours Truly, The One and Only!

[dongxiaofei]

i:) support you

[JudyL_MD]

_NightOwl_ wrote:

to share objects in multiple process, it is best to work with a mutex

It needs to be a named mutex. An un-named mutex is only good for multiple threads in the same process. Judy

[DevMentor org]

You are right Judy :) One should never use a mutex to sync threads in the same process. As I mentioned, critical sections are the best way to go for a multi-threaded process.

Yours Truly, The One and Only!