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. ** Package changed: pm-utils (Ubuntu) => uswsusp (Ubuntu) -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/1098525 Title: Can't complete resume from hibernation unless <Alt><SysRq>+i or <Alt><SysRq>+e is pressed. To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/uswsusp/+bug/1098525/+subscriptions -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs
