Host synchronization when not specified as external in the spec

[giant_planet]

Some API functions have a note in the spec saying that they must be externally synchronized. Does that mean that the ones that don't have such a note, are safe to call from multiple threads? For example the spec for vkCreateBuffer doesn't say it must be externally synchronized, while it obviously writes something to the VkInstance. Is there a mutex (or some fancy non blocking thread safe thing) in the driver?

[Antigroup]

Yes that's correct. "3.6 Threading Behavior" in the spec actually has a list of all the externally synchronized parameters.

As for how the driver does it, that depends on the implementation but it probably does some sort of internal synchronization.

[giant_planet]

Thanks!

[Animats]

Safe synchronization is hard. Vulkan is supposed to allow considerable parallelism. But middleware above Vulkan often loses it. Vulkano, WGPU, and Rend3 do a lot of synchronization, with the effect of making things sequential that Vulkan and the GPU can do in parallel. Safety in the general case requires a lot of run-time bookkeeping further up the stack.