[PATCH] - SMP fixes for i386 kdb

[Jim Houston]

Hi Everyone,

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.

The changes are:

     -	Splitting up the kdb_state variable to 
	decouple data used for inter-processor
	synchronization from local flags.

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

     - 	When several processors enter kdb at the
	same time treat them more as equals.
	My test is to be able to switch to another
	cpu and see useful state and be able to
	single step.  With the released code or
	Ethans patch the inter-processor NMI 
	interrupt may interrupt the kdb entry code.
	This shows up as a confusing backtrace when
	you switch to another processor.


Jim Houston - Concurrent COmputer Corp.
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