Thanks to details of the amdgpu kernel driver, enabling implicit synchronization doesn't actually cause the client to synchronize with itself when doing work on multiple queues. As far as the compositor is concerned, we look just like an OpenGL driver using implicit synchronization and, from the perspective of the Vulkan driver, it all looks like explicit synchronization. Vulkan drivers seamlessly work with compositors which only understand implicit synchronizaiton and, if Wayland compositors pick up sufficient explicit synchronization support, we can transition to that once the compositors are ready.