chvt sometimes hangs, causing hibernation to fail

[Yann Salmon]

This is probably in relation with bug #1350220, which deals with a failure in hibernation. It appears that this is caused by chvt not terminating a some points in the hibernation scripts. Yet I do not know whether the scripts or chvt are to blame.

When I initiate an hibernation on my computer, the following frequently happens (about 50% of the time) :

1. screen goes black (normal) ;
2. instead of showing the progress of the writing of RAM to disk in console mode, the screen remains black ;
3. the screensaver prompt for login appears ;
4. after returning to desktop, I see that the network card is not functioning.

Further debugging (PM_DEBUG=true) shows that the blocking point lies in 99video and is "chvt 63". I tried to hibernate with --quirk-no-chvt. This allows the script 99video to terminate (because it does not try a chvt 63) and the hibernation process itself to engage. However, my hibernation module, /usr/lib/pm-utils/module.d/hibernate, does a chvt 63 too, which is not controlled by the --quirk-no-chvt.

So I experienced again a return to desktop with a chvt process not progressing. I killed it and hibernation took place, without any visual clue. On booting the system again, thaw took place correctly but the system was not usable because I did not get access to a console (graphical or text). Indeed, the pm-suspend.log shows that chvt 8 did not return.

ProblemType: Bug
DistroRelease: Ubuntu 14.04
Package: kbd 1.15.5-1ubuntu1
ProcVersionSignature: Ubuntu 3.13.0-32.57~ppa1-generic-tuxonice 3.13.11.4
Uname: Linux 3.13.0-32-generic-tuxonice x86_64
NonfreeKernelModules: fglrx
ApportVersion: 2.14.1-0ubuntu3.2
Architecture: amd64
CurrentDesktop: XFCE
Date: Sat Aug 2 09:52:13 2014
InstallationDate: Installed on 2014-07-18 (14 days ago)
InstallationMedia: Xubuntu 14.04 LTS "Trusty Tahr" - Release amd64 (20140416.2)
SourcePackage: kbd
UpgradeStatus: No upgrade log present (probably fresh install)

[Launchpad Janitor (janitor)]

Status changed to 'Confirmed' because the bug affects multiple users.

[Malcolm Scott (malcscott)]

chvt makes two ioctl calls, one to change the VT and one to wait for the new VT to become active. There's a race condition here; if something changes the VT back before the second ioctl, chvt will block indefinitely (or until something else changes to the correct VT).