hibernation fails because chvt hangs

EDIT : initial title was "hibernation fails because 99video does not terminate"

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 ;
5. /var/log/pm-suspend.log last line is "Running hook /usr/lib/pm-utils/sleep.d/99video hibernate hibernate:".

Indeed, a ps -ef | grep 99video shows that the /usr/lib/pm-utils/sleep.d/99video script is still running.

If I kill this script, pm-utils logs "/usr/lib/pm-utils/sleep.d/99video hibernate hibernate: Returned exit code 143.", aborts hibernation and then runs the hooks for thaw.

I can then try again to hibernate, and it works : I never had this bug trigger twice in a row.

This bug did not occur when I was running Ubuntu 12.04 and the corresponding kernels (but back then I was also using the video card driver from AMD's website instead of fglrx-updates).

EDIT : further debugging (PM_DEBUG=true) shows that the blocking point in 99video is "chvt 63". I tried to hibernate with --quirk-no-chvt. This allows the script 99video to terminate 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: pm-utils 1.4.1-13ubuntu0.1
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: Wed Jul 30 08:47:17 2014
InstallationDate: Installed on 2014-07-18 (11 days ago)
InstallationMedia: Xubuntu 14.04 LTS "Trusty Tahr" - Release amd64 (20140416.2)
PackageArchitecture: all
SourcePackage: pm-utils
UpgradeStatus: No upgrade log present (probably fresh install)