Can't complete resume from hibernation unless <Alt><SysRq>+i or <Alt><SysRq>+e is pressed.

[Marwan Tanager]

I have Ubuntu 12.10 installed on my Dell Inspiron M5010 Core i3 machine.

When I use pm-hibernate, the computer hibernates successfully, and when
resuming it, the process completes to 100%, but after that nothing seems to
happen, and I stay in the black-and-white text mode screen without any further
activity.

On an attempt to escape this apparent freeze, I tried to press the magic
sequence <ALT><SysRq> + i, and to my surprise, graphics mode is back again to
the same state before hibernation just like one would expect from a normal
resume.

I tried the whole sequence again with <ALT><SysRq> + e, and the same thing
happened (resume completes only after the key combination is pressed).

Actually I am not sure the bug is caused by pm-utils, because after the key
combination is pressed, everything seems to be normal, which means that
pm-hibernate did it's job, but for now, it is the most relevant package as far as I
can tell.

If you need any further info or testing that may be helpful, I'm willing to
cooperate.

ProblemType: Bug
DistroRelease: Ubuntu 12.10
Package: pm-utils 1.4.1-9
ProcVersionSignature: Ubuntu 3.5.0-21.32-generic 3.5.7.1
Uname: Linux 3.5.0-21-generic x86_64
NonfreeKernelModules: wl
ApportVersion: 2.6.1-0ubuntu9
Architecture: amd64
Date: Fri Jan 11 13:02:19 2013
InstallationDate: Installed on 2010-07-29 (896 days ago)
InstallationMedia: Ubuntu 10.04 LTS "Lucid Lynx" - Release amd64 (20100429)
MarkForUpload: True
PackageArchitecture: all
SourcePackage: pm-utils
UpgradeStatus: Upgraded to quantal on 2013-01-06 (5 days ago)

[Marwan Tanager (marwan-tngr)]

It turned out that the problem is in uswsusp. pm-utils uses s2disk and s2ram
from the uswsusp package for hibernation and suspension, and only resorts to
the kernel as a back-end if this package (or the tuxonice patch) is not
installed.

I purged the package and after that pm-hibernate worked as expected without any
hangs.