On Tue, 2012-07-17 at 09:41 -0500, Jason Wessel wrote:
> On 07/16/2012 05:12 PM, Stefan Parlitz wrote:
> 
> > Hi
> > 
> > I'm trying to use KDB with minicom, connected to serial port of a
> > VM.
> > Pressing ctrl-a f g does not activate KDB (it is correctly compiled
> > etc), instead only "g" appears in minicom.
> > 
> > I can enter KDB only by writing:
> > 
> > echo g > /proc/sysrq-trigger
> > 
> > then KDB prompt appears on the serial console and I can use it
> > normally (until "go").
> > 
> > any idea what is wrong?
> > 
> 
> Please report questions and problems to the mailing list, and not me
> directly.
> 
> I am guessing that the sysrq trigger or break sequence is not working
> on your new kernel, either on the host or the target side.
> 
> Not all rs232 devices support a break sequence.  You also didn't
> specify a kernel version, what kind of target system you are using
> etc...
> 
> Cheers,
> Jason.

Hi

thank for your quick response. In fact I have an idea why it might be
broken here - as mentioned I use Vmware to debug stuff and so I use a
Vmware serial port. I think that sending a break on such a port might
just not work correctly:

http://ltxfaq.custhelp.com/app/answers/detail/a_id/736/~/what-is-a-serial-break%3F

it suggest sending a break means that certain timing must appear on the
serial port lines. It might not work like that on emulated Vmware serial
port. However lot of people use this Vmware setup to debug Linux kernel.

is there an easy way to patch kdb to use a "serial string" instead (like
in SGI 4.4 kdb version) - or another key combination? Hardware break is
the worst idea IMO.

thanks.



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