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SubjectRe: [RFC][PATCH] irq0 affinity broke on some i386 boxes
On Fri, 1 Mar 2002, Joe Korty wrote:

> PS: My original dmesg logs may now be found at
> http://www.mindspring.com/~jakorty/irq0.bugreport.orig.

If you only have a line similar to this one:

..TIMER: vector=0x31 pin1=2 pin2=0

then a normal I/O APIC interrupt (pin1) is used and the patch is
irrelevant.

If you have lines like these:

..TIMER: vector=0x31 pin1=-1 pin2=0
...trying to set up timer (IRQ0) through the 8259A ...
..... (found pin 0) ...works.

then IRQ 0 is not registered so far (pin1 is -1) and add_pin_to_irq()
(added by your patch) is invoked ordinarily for pin2 like for other
interrupts.

But if you have lines like these:

..TIMER: vector=0x31 pin1=2 pin2=0
..MP-BIOS bug: 8254 timer not connected to IO-APIC
...trying to set up timer (IRQ0) through the 8259A ...
..... (found pin 0) ...works.

then IRQ 0 needs to be rerouted from pin1 to pin2 and replace_pin_at_irq()
is intended to do so. I'd be pleased to hear from someone with such a
system (they are quite common surprisingly); I'll simulate such a
configuration with my development system anyway.

Other timer configurations (they are two more, sigh) don't matter as they
don't route IRQ 0 via an I/O APIC. They are very rare as well.

Maciej

--
+ Maciej W. Rozycki, Technical University of Gdansk, Poland +
+--------------------------------------------------------------+
+ e-mail: macro@ds2.pg.gda.pl, PGP key available +

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