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Date:      Mon, 15 Sep 2008 22:57:38 -0700
From:      "Scott Gasch" <scott.gasch@gmail.com>
To:        freebsd-amd64@freebsd.org
Subject:   irq19 interrupt storm?
Message-ID:  <a174d0600809152257s31578fa0t6767967da712c189@mail.gmail.com>

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Hi,

I'm running freebsd 7.0-RELEASE-p4 on a 4-core amd64 box. Nearly 100% of
1 cpu is constantly being used handling irq19: uhci4 interrupts. This
seems to happen both with and without any USB devices plugged in:

vmstat -i
interrupt total rate
irq1: atkbd0 5 0
irq6: fdc0 1 0
irq17: mskc0 dc0 1180547 18
irq18: skc0 uhci2* 163250699 2512
irq19: uhci4++ 3187989508 49072
irq23: uhci3 ehci1 31 0
cpu0: timer 129208570 1988
cpu1: timer 129208457 1988
cpu2: timer 125750147 1935
cpu3: timer 125750122 1935
Total 3862338087 59452

dmesg
uhci4: <UHCI (generic) USB controller> port 0xa400-0xa41f irq 19 at device
29.1
on pci0
uhci4: [GIANT-LOCKED]
uhci4: [ITHREAD]


The box runs my own kernel... but a very similar problem happens with
GENERIC.  The same irq (19) is firing too often and consuming nearly all of
one core. But the driver that is associated with the interrupt is different
-- it's fwohci0 this time:

vmstat -i
interrupt total rate
irq6: fdc0 1 0
irq17: mskc0 dc0 313242 13
irq18: skc0 uhci2* 124475451 5540
irq19: fwohci0+++ 957875379 42638
irq23: uhci3 ehci1 1145 0
cpu0: timer 44458513 1979
cpu1: timer 44448875 1978
cpu3: timer 43393901 1931
cpu2: timer 43393921 1931
Total 1258360428 56014


This makes me start to wonder if this is not a problem with irq19 (the
PIC?) and not one particular device / driver. I'm not sure how to make dig
deeper here, any help greatly appreciated.  I posted this to questions a
while back and no one replied ;)

Thx,
Scott



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