[Bug 1304377] [NEW] powernapd runaway

[Sergio Gelato]

Public bug reported:

Very occasionally powernapd runs away on me and starts using almost 100%
of available CPU cycles. I'm running version 2.17-0ubuntu2 on i386,
Ubuntu 12.04.4. The hardware is a Fujitsu Siemens LifeBook S7020 with
BIOS version 1.05.

The last two entries in /var/log/powernap.log are:
2014-04-08_12:49:54 WARNING  Taking action [/usr/sbin/powernap]
2014-04-08_13:54:37 WARNING  Taking recover action [/usr/sbin/pm-powersave false]

I assume that something goes wrong during the transition away from
powersave.

Attaching to the running /usr/sbin/powernapd process with gdb yields the
following backtrace:

#0  0x002b5416 in __kernel_vsyscall ()
#1  0x00549bd1 in select () at ../sysdeps/unix/syscall-template.S:82
#2  0x080fbdf3 in time_sleep.52928 ()
#3  0x08137591 in PyEval_EvalFrameEx ()
#4  0x08137abc in PyEval_EvalFrameEx ()
#5  0x0813da90 in PyEval_EvalCodeEx ()
#6  0x0813e361 in run_mod ()
#7  0x0813e851 in PyRun_FileExFlags ()
#8  0x08087565 in PyRun_SimpleFileExFlags ()
#9  0x0808909f in Py_Main ()
#10 0x0805eabb in main ()

I'm attaching a few seconds' worth of strace output.

My only workaround so far is to run
service powernap restart
(or equivalent) whenever this happens. Unfortunately I don't know how to reproduce the problem at will.

** Affects: powernap (Ubuntu)
     Importance: Undecided
         Status: New

** Attachment added: "powernap.trace"
   https://bugs.launchpad.net/bugs/1304377/+attachment/4074620/+files/powernap.trace

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https://bugs.launchpad.net/bugs/1304377

Title:
  powernapd runaway

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