[PATCH] - SMP fixes for i386 kdb

[Keith Owens]

On Thu, 16 May 2002 20:34:07 -0400, 
Jim Houston <jim.houston at ccur.com> wrote:
>The attached patch is an update of my earlier patch
>to fix smp problems in kdb.  I started with Ethan
>Solomita's patch but I have change a lot of code
>since then. I have been exchanging private email with
>Ethan over the last week and he has helped find some
>of my bugs.  Thanks again.  There are always more bugs
>but I think this patch has reached the useful stage.

I finally got time to spend on kdb, my apologies for not answering
these patches sooner.

Jim, Ethan, is this a common patch or do you still have differences of
approach?

>The changes are:
>
>     -	Splitting up the kdb_state variable to 
>	decouple data used for inter-processor
>	synchronization from local flags.

Good idea.

>     -	Avoid having an extra layer of nesting
>	if a processor is already in kdb when the
>	kdb inter-processor interrupt is delivered.

I agree with the aim but am a bit unhappy with putting the code in
entry.S.  Patching the assembler closes the window between int3 and NMI
to a few instructions, at the cost of extra asm.  Moving the kdb_in_kdb
setting to do_int3 will use C instead of asm.  It is a trade off, a
slightly larger window for easier to maintain code.