hard-lock with CPU spinning

Attilio Rao attilio at freebsd.org
Thu Jun 14 16:36:19 UTC 2007

2007/6/14, Giorgos Keramidas <keramida at ceid.upatras.gr>:
> If I leave my laptop idle for a long period of time, it tends to lock up
> with the CPU fan spinning fast (presumambly because some part of the
> kernel tries to acquire a lock and spins constantly for it).
> Unfortunately, this happens when X11 is running and I can't break into
> DDB to snoop around.
> I did notice that if I leave a terminal running:
>    $ while true ; do \
>          echo -n "$(date '+%Y-%m-%d %H:%M') " ; \
>          tail -1 /var/log/messages ; \
>          sleep 10 ; \
>      done
> this works as a 'workaround' for the hardlock.
> The sources of /usr/src have been updated up to:
>    2007.
> Any ideas how I could try to debug this?

Recompile the kernel with DDB support (pay attention to disable
KDB_UNATTENDED), additionally add WITNESS support (paying attention to
not add WITNESS_SKIPSPIN), even if this wouldn't help in direct
Then, when the kernel hangs, just break into the debugger and print
out bt, show alllocks, ps.
This would give a reasonable start.


Peace can only be achieved by understanding - A. Einstein

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