GL_EXT_semaphore Being Prepped For Mesa, Used By SteamVR

Andres Rodriguez of Valve has posted a set of 17 patches for implementing the OpenGL GL_EXT_semaphore extension within Mesa and wired through for RadeonSI.

GL_EXT_semaphore is part of the OpenGL memory object support that was introduced as an extension this year for porting these semaphores / memory objects concepts from Vulkan back to OpenGL. Semaphores are synchronization primitives and the GL semaphores map to the semantics of Vulkan semaphores.

Valve is using the EXT_semaphore extension by their SteamVR client to synchronize access to shared surfaces between Vulkan and OpenGL.

The set of 17 patches and thousand new lines of code to be added to Mesa can be found via Mesa-dev.

Meanwhile, NVIDIA's Linux driver has already supported OpenGL memory objects and semaphores since back in June.