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Date:      Thu, 14 Jun 2007 18:36:17 +0200
From:      "Attilio Rao" <attilio@freebsd.org>
To:        "Giorgos Keramidas" <keramida@ceid.upatras.gr>
Cc:        current@freebsd.org
Subject:   Re: hard-lock with CPU spinning
Message-ID:  <3bbf2fe10706140936r4458343do95aa9f16baf2e79a@mail.gmail.com>
In-Reply-To: <20070614161632.GA3385@kobe.laptop>
References:  <20070614161632.GA3385@kobe.laptop>

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2007/6/14, Giorgos Keramidas <keramida@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:
>
>    2007.06.12.15.37.17
>
> 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
analysis.
Then, when the kernel hangs, just break into the debugger and print
out bt, show alllocks, ps.
This would give a reasonable start.

Thanks,
Attilio


-- 
Peace can only be achieved by understanding - A. Einstein



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