kernel debugger and usb keyboard

[Hans Petter Selasky]

On Saturday 22 August 2009 16:48:07 Bruce Cran wrote:
> On Mon, 3 Aug 2009 21:27:30 +0200
>
> Hans Petter Selasky <hselasky at c2i.net> 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".
> >
> > 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!
>
> USB keyboard support is now working in the debugger, but it seems
> the USB stack hangs up if you exit out of the debugger, if the system
> hasn't crashed and can keep running - the keyboard doesn't respond, and
> unplugging and re-plugging it doesn't help.
>
> If I press Ctrl-Alt-Esc followed by "c" to continue, the output scrolls
> up the window as if the Enter key is being held down.

This is going to get fixed in a coming USB patchset. Stay tuned.

--HPS