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Date: Mon, 03 Aug 2009 15:03:07 -0700
From: Julian Elischer <julian@elischer.org>
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To: Hans Petter Selasky <hselasky@c2i.net>
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Cc: Alexander Best <alexbestms@math.uni-muenster.de>, freebsd-usb@freebsd.org
Subject: Re: kernel debugger and usb keyboard
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Hans Petter Selasky wrote:
> On Monday 03 August 2009 20:55:16 Alexander Best wrote:
>> just tried settings `sysctl debug.kdb.panic = 1`. if i use this way to
>> enter the kernel debugger my usb keyboard works. if i type "continue"
>> however the kernel panics and the kernel debugger gets yet entered again,
>> but without the keyboard working.
> 
> The USB controller which the keyboard is hooked onto will not work after panic 
> has been entered, due to some state not being cleaned up.
> 
> To increase the chance of the keyboard working on a panic, connect the 
> keyboard to a separate USB controller. 
> 
>> i don't know how to produce backtraces since the keyboard doesn't work.
> 
> Ok.
> 
>> the other way of entering the debugger without my keyboard working was to
>> simple press "ctrl+ast+esc".

try entering it from the sysctl debug.kdb.enter
(set it to 1)

> 
> Yes, because most likely the DDB is entered directly from the USB keyboard 
> code, and the USB stack does not allow function recursion in that case!
> 
> --HPS
> 
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