linux-kernel - Re: strange SysRq problem

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Date:	Thu, 14 Feb 2008 15:28:11 +0100
From:	Hans-Peter Jansen <hpj@...la.net>
To:	linux-kernel@...r.kernel.org
Cc:	Arnd Hannemann <hannemann@...informatik.rwth-aachen.de>
Subject: Re: strange SysRq problem

Am Donnerstag, 14. Februar 2008 schrieb Arnd Hannemann:
> Hans-Peter Jansen wrote:
> > I'm suffering from a strange SysRq problem:
> >
> > syslog shows haphazardly "SysRq : HELP" lines, while I definitely
> > didn't triggered them, neither via (PS/2) keyboard, nor via
> > /proc/sysrq-trigger. This is accompanied with stalls of about 15-60
> > secs.
>
> Any chance that a device connected via serial (or an USB device which
> uses USB/Serial conversion) triggers them? My cheap pl2303 device seems
> to send spurious BREAKs every once in a while, which results in the
> described behavior, as the kernel will print the help line for any
> character which is not a valid sysrq. (The probability to trigger another
> sysrq with random data is much lower, but did you find any other printout
> of an sysrq in your logs?)

Hmm, keyboard (Cherry G80-3000 LPCDE-2) and mouse (Logitech RX300) are 
connected via an equip KVM 2 port switch, but everything else is behaving 
properly, and no serial devices connected ATM. It only triggers the help 
messages, other sysrq messages are triggered at will (AFAIKS).

# grep "SysRq : HELP" /var/log/messages | wc -l
814

syslog starts at Jan 16, so you can imagine how disturbing this behavior is.

I cannot outrule some hardware defects. Will start to eliminate the KVM 
switch, but I thought, I ask here before since google also didn't revealed 
any hints..

Thanks,
Pete
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