Locking a non-thread-safe DLL, innovative solutions?

Question

Hi,
I need to be able to lock access to a non-thread-safe third party DLL, so that multiple threads cannot access DLL simultaneously. I know that I can use semaphore or a single element queue. Are there any other innovative solutions that would limit the access to the DLL to a single call simultaneously.
If I use either semaphores or single element queue and use the semaphore (queue) with the same name in multiple programs (independent VIs), will the access to the DLL be handled without problems i.e. no collisions can happen? What if I build multiple applications (.exe) or application libraries (.dll), does a single semaphore (queue) still work between different applications or do they need to be initiated from the same application?
Tomi
Message Edited by Tomi M on 03-06-2006 08:01 PM
Tomi Maila

Answer 1

Tomi M wrote:
One more thing, with
innovative solutions I meant something like the following. Is there a
way to use some properties of Labview execution system to automatically
restrict the access to the DLL i.e. allow only single thread with
certain properties to call the DLL while all other threads with the
same properties are waiting in the execution queue. So if I set the
execution priority to something specific and execution system to
another something specific, will Labview thisway restrict access to DLL
to be sequential?
The proper way to
call non multithread safe DLLs in LabVIEW is to configure the Call
Library Node in the configuration dialog to be NOT reentrant. This
tells LabVIEW that the DLL may behave badly or at least you do not want
LabVIEW to call the DLL just from any thread. LabVIEW then will call
this DLL function from the UI execution system which is guaranteed to
only have one single thread at all times and therefore protect your DLL
from being called frm different threads at the same time.
Rlf Kalbermatter
Rolf Kalbermatter
CIT Engineering Netherlands
a division of Test & Measurement Solutions