Re: [PATCH 9/11] Panic delay fix

Dmitry Torokhov
2007-02-07T14:59:12Z

On 2/6/07, Zachary Amsden <zach@vmware.com> wrote:
> Andi Kleen wrote:
> > On Mon, Feb 05, 2007 at 07:53:30PM -0800, Zachary Amsden wrote:
> >
> >> Failure to use real-time delay here causes the keyboard to become demonically
> >> possessed in the event of a kernel crash, with wildly blinking lights and
> >> unpredictable behavior. This has resulted in several injuries.
> >>
> >
> > There must be a reason why it wasn't default before. Has this
> > reason changed?
> >
>
> This only matters under paravirt; non-paravirt kernels and kernels
> running on native hardware will always behave properly.
>
> But paravirtualized kernels with fake devices have no need to udelay to
> accommodate slow hardware - the hardware is just virtual. The
> USE_REAL_TIME_DELAY define allows udelay to be specifically reverted
> back to being a real delay. There are only a couple cases where it
> matters - one is booting APs on SMP systems (there is a real delay
> before they come up), and one is any hardware that drives world
> interacting devices - such as keyboard LEDs in a panic loop.
>

I am confused - does i8042 talk to a virtual or real hardware here? In
any case I think you need to fix kernel/panic.c to have proper
(m)delay, not mess with i8042.

--
Dmitry