https://bugs.freedesktop.org/show_bug.cgi?id=107928
--- Comment #10 from Matthew Vaughn nethershaw@gmail.com --- I've determined that the deadlock and stack trace found in my dmesg logs is emitted precisely when I attempt to wake the machine's display from sleep by touching the keyboard or mouse, and not before.
If I leave the machine on a terminal console instead of in a running X session, the display never sleeps, and the deadlock never occurs.
The first instance of the deadlock on my machine occurred during a session following an upgrade of the xf86-video-amdgpu drivers from version 18.0.1 to 18.1.0, and simultaneously, of Mesa to a checkout of the master branch ca. commit 0d495bec25bd7584de4e988c2b4528c1996bc1d0, or approximately 2018-09-26 04:16 UTC. I am attempting now to revert both of these upgrades one at a time in order to determine whether either of them is implicated.