How do I find the application which is locking suspend?

After fresh restart this command allows to suspend, but only once.
Look. I run this command. Computer suspends. I wake it up, the command is locking terminal. I press Ctrl+C. Then I only run it again, but it doesn't suspend anymore.

Code: Select all

$ dbus-send --system --print-reply --dest="org.freedesktop.UPower" /org/freedesktop/UPower org.freedesktop.UPower.Suspend
# here it sleeps but doesn't finish after sleeping
^C
$ dbus-send --system --print-reply --dest="org.freedesktop.UPower" /org/freedesktop/UPower org.freedesktop.UPower.Suspend
# here it doesn't sleep anymore, though I didn't start any applications
Error org.freedesktop.UPower.GeneralError: Sleep has already been requested and is pending

I see. Can you examine the full list of processes on your system before and after suspending it, to see if there are any commands which are hanging?
The bug in this case is likely somewhere at the system level - in UPower or in the stack responsible for performing the actual suspend.

I'm not sure if it is a reason, but after suspending I have 71 new processes of kworker. They are called 'kworker/u8:N', where N are the numbers from 9 to 79.

No, they are not the reason. For now they all have died, but suspend still is not working.

"kworker" processes are kernel processes used by drivers and other parts of the kernel to perform tasks - they won't be related to the suspend issue.

Thank you for your help, the output of commands suggested by you helped to find the bug in debian bugzilla: http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=718458
Now I'll go there, finally it is not KDE at all

same like me, every upgrading i have any problem on my KDE