On Fri, Sep 20, 2019 at 1:32 AM Derek Lesho <dlesho@codeweavers.com> wrote:

Also, in your patch, I noticed that you intentionally unlock before
performing the copy or overwrite. This puzzles me, if one thread waits
on the global mutex for access to a descriptor's view to dereference,
and we unlock the mutex for them when the view is NULL, they may crash
when trying to decrement the reference of the NULL view.

Yes, it's missing a null check after locking the mutex. If it's null after locking then the function can return because it means another thread has destroyed the descriptor. I think the only remaining problem is the old one of a single mutex being used for all descriptors. Maybe performance can be improved.