One further historical detail: when these machines were running 14.04.3 and we made the mistake of accepting the HardWare Enablement (HWE) upgrade:
https://wiki.ubuntu.com/1404_HWE_EOL which replaced the old fglrx driver with the radeon one, that's when we first encountered this unable-to-unblank problem. Fortunately, at that time we were able to roll back Xorg to 1.16 and keep things sort-of working: https://askubuntu.com/questions/815591/ubuntu-14-04-5-16-04-and-newer-on-amd-graphics https://askubuntu.com/questions/676216/downgrade-xorg-server When we performed a clean, full re-install with 16.04 we were hoping this problem would be resolved, but as I've documented here it continues to affect the systems. -- You received this bug notification because you are a member of Ubuntu Touch seeded packages, which is subscribed to xorg in Ubuntu. https://bugs.launchpad.net/bugs/1763273 Title: kernel panic in Radeon driver while screen blank Status in linux package in Ubuntu: Incomplete Status in xorg package in Ubuntu: Confirmed Bug description: I maintain a set of older kiosks running a mix of stock Ubuntu 14.04 LTS and 16.04. As we have gradually transitioned them to 16.04, we have noticed that the machines running 16.04.1 now regularly exhibit problems restoring from the blank screen which appears after a period of inactivity. This only occurs on the machines where we've installed 16.04. All of the 16.04.1 installations are "fresh", that is, complete re-installs from scratch, and we install all security and other updates on a regular basis. This problem has persisted right from the beginning when we started using 16.04. Following a period of user inactivity, the screen goes blank; this is, of course, expected. When the user tries to restore the session by typing a key or moving the mouse, one of three outcomes occurs. Sometimes, the session restores normally. Other times, the screen remains blank regardless of all normal keyboard input, until a magic SysRq sequence is performed. After Alt-SysRq-k, either the virtual console resets to a login screen (as expected after this SysRq sequence), or we get a kernel panic text screen (see attached screen photo) and can only restore via a hard power-cycle reboot. I will continue to try to capture a better trace output from one of these conditions, perhaps from /var/log/kern.log or by installing linux-crashdump (although these old machines may not have enough memory for the stock package). But in the meantime, I'm attaching a photo of the kernel panic we see, which suggests a problem may reside in the Radeon driver ... which would seem possible, given the general blank-screen no-resume problem on these systems. Any advice on how to further capture any other needed details would be appreciated. Thanks very much! To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1763273/+subscriptions -- Mailing list: https://launchpad.net/~touch-packages Post to : touch-packages@lists.launchpad.net Unsubscribe : https://launchpad.net/~touch-packages More help : https://help.launchpad.net/ListHelp
