Reproject in multiprocessing

In my code, I have several images to reproject to a certain WCS. So I want to using multiprocessing pool to accelerate this procedure.
I pass the CCDData and target WCS to a function and it returns a new CCDData to main thread.
The problem is the program is always stuck at the last few images. When I commented out the reproject_interp all thing run good.

Start with a minimal multiprocessing pool reproducer using several CCDData images, a target WCS, and reproject_interp. Compare the run with and without reproject_interp, then inspect where the final workers stop responding. Done means the hang is reproduced and its triggering conditions or cause are documented.

Written by the indexing model from the issue text.