Comment # 8 on bug 935086 from Uwe Geuder

Created attachment 638634 [details]
screen picture when resume from hibernate hangs + SysRq

I use systemctl hibernate to hibernate the system. (Originally I used KDE
desktop to call hibernate from the GUI. The hang existed already there with the
same symptoms. Recently I have switched to i3 window manager and I call
systemctl hibernate from command line).

When the system hangs in resume SysRq just prints the headlines, but no
information. (see attached screen shot) What does that mean?

While experimenting with SysRq I noticed that "SysRq i" (SIGKILL to all) makes
the resume complete. (tried twice, worked twice) The system seemed functional
after that, but I did not dare to really use it, because I'm not sure what
might be in an inconsistent state after the killing. What can we learn from
that? I guess it means that the hang was still in initramfs, so killing all
initramfs processes made it resuming the real root. But I don't understand the
details how the real root could come up when everything is killed. 

(After the resume had completed SysRq showed the complete information, not just
the headlines.

I also tried "echo disk | sudo tee /sys/power/state". In this case the system
does not hang when resuming. What do we learn from that?