IRQ21 flood on nForce2

[Noel Maddy]

Howdy,

I'm getting over 100k interrupts/second on IRQ21 on an nForce2
motherboard any time I have a driver using that interrupt.

Both ehci_hcd and intel_8x0 use that interrupt. When either or both
modules are loaded, it looks like below. With no modules loaded, or with
pci=noacpi, behavior is fine.

I've filed more detail at buzilla, including dmidecode and acpidmp
output:

http://bugzilla.kernel.org/show_bug.cgi?id=2574

Seems like it'd be something with the ACPI/interrupt configuration, yes?

Noel

-------------

cat /proc/interrupts
           CPU0       
  0:     706031    IO-APIC-edge  timer
  1:          8    IO-APIC-edge  i8042
  2:          0          XT-PIC  cascade
  7:          0    IO-APIC-edge  parport0
  8:          4    IO-APIC-edge  rtc
  9:          0   IO-APIC-level  acpi
 12:         50    IO-APIC-edge  i8042
 14:       4742    IO-APIC-edge  ide0
 18:          0   IO-APIC-level  EMU10K1
 19:          3   IO-APIC-level  Bt87x audio, bttv0
 20:      76147   IO-APIC-level  ohci_hcd, eth0
 21:  104487700   IO-APIC-level  ehci_hcd, NVidia nForce2
 22:          0   IO-APIC-level  ohci_hcd
NMI:          0 
LOC:     705958 
ERR:          0
MIS:          0

vmstat 1 10
procs -----------memory---------- ---swap-- -----io---- --system-- ----cpu----
 r  b   swpd   free   buff  cache   si   so    bi    bo   in    cs us sy id wa
 2  0      0 396560   5804  51848    0    0    77    25 27446    46 95  1  3  1
 1  0      0 396560   5804  51848    0    0     0     0 117260     9 100  0  0  0
 1  0      0 396560   5804  51848    0    0     0     0 117333     8 100  0  0  0
 1  0      0 396560   5804  51848    0    0     0     0 117333     6 100  0  0  0
 1  0      0 396560   5804  51848    0    0     0     0 117335     8 100  0  0  0
 1  0      0 396560   5812  51848    0    0     0    60 117334    12 100  0  0  0
 1  0      0 396568   5812  51848    0    0     0     0 117335     8 100  0  0  0
 1  0      0 396568   5812  51848    0    0     0     0 117336    10 99  1  0  0
 1  0      0 396568   5812  51848    0    0     0     0 117343     6 100  0  0  0
 1  0      0 396568   5812  51848    0    0     0     0 117334     6 100  0  0  0

cat /proc/interrupts
           CPU0       
  0:     715191    IO-APIC-edge  timer
  1:          8    IO-APIC-edge  i8042
  2:          0          XT-PIC  cascade
  7:          0    IO-APIC-edge  parport0
  8:          4    IO-APIC-edge  rtc
  9:          0   IO-APIC-level  acpi
 12:         50    IO-APIC-edge  i8042
 14:       4744    IO-APIC-edge  ide0
 18:          0   IO-APIC-level  EMU10K1
 19:          3   IO-APIC-level  Bt87x audio, bttv0
 20:      77101   IO-APIC-level  ohci_hcd, eth0
 21:  105550345   IO-APIC-level  ehci_hcd, NVidia nForce2
 22:          0   IO-APIC-level  ohci_hcd
NMI:          0 
LOC:     715119 
ERR:          0
MIS:          0


-- 
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+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
Noel Maddy <noel@xxxxxxxxx>
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