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).
Created attachment 126725 [details]
Valgrind output when replaying trace
Valgrind reports a use after free error when the unmap occurs.
You like to live dangerously :)
I can reproduce and will look into this, thank you for the clean report!
A candidate fix is here: https://patchwork.freedesktop.org/series/12982/
A can confirm that patch series fixes the issue.
Fixed in Mesa master (commit e56e1f8119f28eebbe6fbe7040c80a6dd884f5fd).