Re: linux-next: Tree for June 13: IO APIC breakage on HP nx6325

From: Rafael J. Wysocki
Date: Wed Jun 18 2008 - 18:10:37 EST


On Wednesday, 18 of June 2008, Maciej W. Rozycki wrote:
> On Wed, 18 Jun 2008, Rafael J. Wysocki wrote:
>
> > Here you go. Below is the relevant snippet from the yesterday's linux-next
> > dmesg with the patches:
> > "x86: I/O APIC: timer through 8259A second-chance"
> > "x86: add C1E aware idle function"
> > reverted and the appended debug patch applied.
> >
> > [ 0.108006] TIMER: vector=0x30 apic1=0 pin1=2 apic2=-1 pin2=-1
> > [ 0.108006] ..MP-BIOS bug: 8254 timer not connected to IO-APIC
> > [ 0.108006] ...trying to set up timer (IRQ0) through the 8259A ... <2> failed
> > [ 0.108006] ...trying to set up timer as Virtual Wire IRQ...<2> works.
> >
> > The entire dmesg is at: http://www.sisk.pl/kernel/debug/20080616/dmesg-4.log
>
> Thanks -- this is very important and useful information as it shows the
> exact alternative used.
>
> With such a configuration the "x86: I/O APIC: timer through 8259A
> second-chance" patch should not matter, because the only change it
> introduces is an attempt to try the same I/O APIC pin again, but with the
> IRQ0 line of the master 8259A enabled. That's not a terribly unusual
> configuration and nothing should get confused in the system.

But it _does_ get confused, really.

> Barring the unlikely possibility of the 8259A actually being wired to
> INTIN2 of the I/O APIC I can see two possible explanations:
>
> 1. The 8259A interrupt actually escapes to the CPU somehow and is handled
> as an ExtINTA interrupt. This would make the code in check_timer()
> decide it has found a working configuration, while actually it has been
> fooled.
>
> 2. There is a bug in this patch or an assumption it makes which results
> in the state of some component not to be restored correctly.
> Unfortunately I have no resources to test the 64-bit variation of the
> code, so something may have escaped my attention.
>
> I'd like to find out which one is the case -- can you please reapply the
> patch and send me the corresponding section of the bootstrap log? If the
> system hangs before you can retrieve the log, please just place:

Here you go:

[ 0.108006] ..TIMER: vector=0x30 apic1=0 pin1=2 apic2=-1 pin2=-1
[ 0.108006] ..MP-BIOS bug: 8254 timer not connected to IO-APIC
[ 0.108006] ...trying to set up timer (IRQ0) through the 8259A ... <3>
[ 0.108006] ..... (found apic 0 pin 2) ...<3> works.

The full dmesg is at: http://www.sisk.pl/kernel/debug/20080618/dmesg-1.log

Thanks,
Rafael
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