On Thu, 16 May 2002 20:34:07 -0400,
Jim Houston <jim.houston@xxxxxxxx> 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.
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