(In reply to Jaap Buurman from comment #142)
> How can I set both AMD_DEBUG=nongg and AMD_DEBUG=nodma in the
> /etc/environment file? Do they need to be on two separate lines, or will the
> second line simply overwrite the first one by setting the same environment
> variable? Do they need to be comma separated maybe?

AMD_DEBUG="nodma nongg"

I've been running like this since I found this bug report. Current uptime:
11:08:41 up 4 days,  4:12, 11 users,  load average: 8,56, 8,33, 8,15

Haven't experienced a single hang, not even a kernel oops. Before that, the
system was frustratingly unstable. If you need stability, put this in
/etc/environment (or /etc/env.d/99amdgpu or so if your distro supports
/etc/env.d).

Running on Gentoo, kernel 5.3.4, mesa 19.2.1, llvm 9.0.0, libdrm 2.4.99,
xf86-video-amdgpu git e6fce59a071220967fcd4e2c9e4a262c72870761.