Operating in a Multithreaded Environment
The fax service calls FaxDevStartJob at the beginning of a new fax job and once for each fax operation, because each operation executes in a separate thread. Fax service providers (FSPs) must function in a multithreaded environment.
The FSP must allocate memory for the job-specific instance data for each fax operation thread to ensure that the FSP DLL is thread-safe. The FSP should also deallocate memory for the instance data when the fax operation finishes. For more information, see Multiple Threads.