Created attachment 117967 [details]
dmesg with added debug output

I've done some more testing, turns out that it never reaches
amdgpu_ring_unlock_commit on certain cases, and that's what causes it to hang,
since the mutex never unlocks.
I added some debug output to the code, gfx/sdma0 is ring->name, 0/9 is
ring->idx and the address is the address of the ring struct.
As you can see in the log, it calls amdgpu_ring_lock on ring 9 with name sdma0,
and then afterwards it calls it again on ring 0 with name gfx, without calling
amdgpu_ring_unlock_commit.
I will add some more debug output in hopes of finding why exactly it's never
unlocked, and if it is fixable. I should mention that these random lockups do
not happen while using the proprietary catalyst driver, so it must be something
in the amdgpu driver.