Comment 51 for bug 1419355

(In reply to Niklas Schnelle from comment #45)
> Ok, I will open a new bug report as soon as I've got a little more time on
> my hands. I still think it's related with this issue though, because without
> the quirk i.e. with older kernels or witch the patch from comment 16 I get
> somewhat 50% correct shutdowns while with the HP quirk, that is newer
> kernels without the patch I consistently get 100% reboots.

I suppose except for this bug #66171, you have some kernel unrelated issue too.

Suggest try to find this issue:

1, Test kernel 3.11 or before, don't start the GUI desktop(like gnome, kde, xfce, etc.), this can be done by forbid GUI login service(e.g., sudo chmod -x /etc/init.d/gdm3). Then poweroff machine under text console with command: sudo shutdown -h now;

2, Test with other distro LiveCD with kernel 3.11 or before;

3, Install a fresh Linux only with command line, no X;

4, Remove all power managment components, such as: acpid, pm-utils, cpufreq-utils, etc..