https://bugs.freedesktop.org/show_bug.cgi?id=101384
--- Comment #5 from Nicolai Hähnle nhaehnle@gmail.com --- Created attachment 131900 --> https://bugs.freedesktop.org/attachment.cgi?id=131900&action=edit possible fix
As discussed on IRC, the error goes away when dumping shaders, which means that the bug might be related to multi-threading. This suggests the attached patch.