Created attachment 126724 [details]
Apitrace reproducing issue

The following sequence of events cause a crash on radeonsi:
1. Create two contexts in the same share group
2. In one of the contexts, create and map a buffer. Then delete that context.
3. Create another context in the share group
4. Cause the buffer to be unmapped in the new context (either explicitly with
glUnmapBuffer/glUnmapNamedBuffer or implicitly via glDeleteBuffers).

The attached apitrace reproduces the issue when using an AMD R9 270, unless
environment variable LIBGL_ALWAYS_SOFTWARE is set to 1.

I reproduced this using Mesa git 36f0f0318275f65f8744ec6f9471702e2f58e6d5 and
the 12.0.3 release on x86_64 Fedora 24.
My OpenGL renderer string is Gallium 0.4 on AMD PITCAIRN (DRM 2.45.0 /
4.7.2-201.fc24.x86_64, LLVM 3.9.0).