How to Use ddb(4)?

John Baldwin jhb at
Thu Jul 27 21:40:21 UTC 2006

On Thursday 27 July 2006 15:04, Hans Petter Selasky wrote:
> On Thursday 27 July 2006 20:40, Dag-Erling Smørgrav wrote:
> > maksim yevmenkin <maksim.yevmenkin at> writes:
> > > Dag-Erling Smørgrav <des at> writes:
> > > > No, kbdmux needs to be fixed so it works in DDB.
> > >
> > > actually, atkbd(4) needs to be fixed to support "polled" mode :)
> >
> > It used to work fine before kbdmux(4) came along...
> >
> Just a comment: Don't forget to lock Giant before calling anything in the 
> keyboard layer. That means DDB must lock Giant, else at least my new USB 
> keyboard driver will panic, saying Giant is not owned. The old USB keyboard 
> driver did not care about this.

DDB should not be acquiring locks or depend on being able to do so.  When you 
panic the machine is an unknown state for one, and you really want to leave 
the overall system state as undisturbed as possible while in the debugger to 
aid in debugging.

John Baldwin

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