tree b3ea2730be2abf6cc5bcc5e62b1408d3a67fd5b3
parent a5cefa5c98a6c1a80bb52a55a189dcbb7b1cfdb0
author Bill Hollings <bill.hollings@brenwill.com> 1561930132 -0400
committer Bill Hollings <bill.hollings@brenwill.com> 1561930132 -0400

Fix race condition between swapchain image destruction and presentation completion callback.

Retain MVKSwapchainImage before passing to MTLCommandBuffer completion handler.
Redesign MVKVulkanAPIObject retain/release functionality using atomic ref count
instead of mutex locks, to simplify design and improve performance.