The submit waits the Vulkan-Video frame's decode-complete timeline semaphore
at FRAGMENT_SHADER, but the acquire barrier ran its layout transition
(VIDEO_DECODE_DST/DPB -> SHADER_READ_ONLY) from srcStage TOP_OF_PIPE — which
the wait does not cover, so no dependency chain formed and the transition
could execute while the decode queue was still writing the image. The race
window is real: the pump ships each frame to the presenter BEFORE its
decode-complete wait (that wait is stats-only).
On RADV the transition physically touches the image (metadata /
decompression), so the race rendered green/yellow block corruption exactly
at freshly-decoded regions — the Steam Deck 'artifacts around the moving
cursor' bug (the cursor is the only damage on an idle desktop). NVIDIA
treats the transition as a no-op, which is why the identical code looked
clean on the dev box.
srcStage is now FRAGMENT_SHADER, matching the semaphore's wait mask — the
standard acquire pattern (same as swapchain acquires) that chains the
transition after the decode signal.
Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
enricobuehler
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