kernel debugger and usb keyboard
julian at elischer.org
Mon Aug 3 22:16:33 UTC 2009
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.
>> 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!
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