Further debugging today while I'm on-site with the kiosks. The system froze, as usual, after normal idle screen blanking. I was able to login via ssh and retrieve some details.
First, it appears that the basic screen blanking problem is somehow related to the Radeon driver. I will attach the Xorg.0.log file and a gdb backtrace on the running but non-responsive Xorg process. No keyboard or mouse activity will un-blank the screen. Here's the output from lspci | grep VGA: 01:00.0 VGA compatible controller: Advanced Micro Devices, Inc. [AMD/ATI] RV516 [Radeon X1300/X1550 Series] I'll also attach the PCI ROM dump from the /sys/devices rom file for this device. This suggests that when we use Alt-SysRq-k to restore the system, sometimes we trigger *another* bug in the driver which results in the overall system crash. See the attached apr1.full.kern.log file for what details I could recover from the crash on April 1st; that corresponds to the screen photo I took that day (the radeon_kernel_panic1.jpg attachment). The Xorg "hang" bug which precedes this appears similar, but not identical, to what is documented in #1664979: https://bugs.launchpad.net/ubuntu/+source/xorg/+bug/1664979 I will continue to try to study the live Xorg process to see if I can determine where its hung, but I may not have time this evening. Let me know if there are specific further debugging steps I can take to examine either the Xorg hang or the subsequent crash which (sometimes) follows on attempting to recover with Alt-SysRq-k. (And note that I'll copy in the files apport-bug generated from #1764211 later tonight, using my "cdarroch" personal account, and then I'll try to close that extra bug report.) Thanks very much, Chris. -- You received this bug notification because you are a member of Desktop 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: New 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/~desktop-packages Post to : email@example.com Unsubscribe : https://launchpad.net/~desktop-packages More help : https://help.launchpad.net/ListHelp