Spurious interrupts on eepro100 1.06/2.2.1/SMP

[Andi Kleen]

Hallo,

I'm using the eepro100.c 1.06 driver as shipped in 2.2.1 on a SMP
machine. I noticed that the interrupt count in /proc/interrupts
increases by one about every 2-3 seconds, even though there
is no traffic on the network and no packets send out (RX/TX counters zero,
only active node on the net). The interrupt is a IO-APIC interrupt and
is not shared.

/proc/interrupts: 
  0:     346620     350409    IO-APIC-edge  timer
  1:       8031       8460    IO-APIC-edge  keyboard
  2:          0          0          XT-PIC  cascade
  4:       8545       8657    IO-APIC-edge  serial
  5:          1          1    IO-APIC-edge  NE2000
 13:          1          0          XT-PIC  fpu
 15:      33948      31790    IO-APIC-edge  HiSax
 16:       6521       6452   IO-APIC-level  aic7xxx
 18:          0          0   IO-APIC-level  es1371
 19:       1707       1775   IO-APIC-level  Intel EtherExpress Pro 10/100 Ethernet
                      ^^^^ This number increases steadily    
NMI:          0
ERR:          0

Module output:

eth1: Intel EtherExpress Pro 10/100 at 0xe800, 00:A0:C9:30:39:BC, IRQ 19.
  Board assembly 661949-004, Physical connectors present: RJ45
  Primary interface chip DP83840A PHY #1.
  DP83840 specific setup, setting register 23 to 8462.
  General self-test: passed.
  Serial sub-system self-test: passed.
  Internal registers self-test: passed.
  ROM checksum self-test: passed (0x49caa8d6).
  Receiver lock-up workaround activated.

Could anyone explain this?

-Andi