SIO Interrupt storms and unhanded interrupts
From: Mike Tancsa (mike_at_sentex.net)
Date: 09/09/04
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Date: Wed, 08 Sep 2004 19:25:48 -0400 To: freebsd-current@freebsd.org
I think we have been bouncing around this issue for the past few months
both on RELENG_4 and now RELENG_5. In the past it has been somewhat
difficult to reproduce, but now we can do it reliably. I dont think its
a hardware issue as I can take the exact same 2 boxes with the exact same
IRQ assignments and boot with OpenBSD and not run into an interrupt storm
or freeze up the box. Swap back the RELENG_4 or RELENG_5 HD and again, I
can produce an interrupt storm at will.
I can also reproduce it on 2 different chipsets as well (VIA and
Intel). The problem seems to be around how a PUC device (either a PCI
modem or a PCI serial card) and the sharing of an interrupt (usually an USB
controller, but not always).
On RELENG_4, the box just locks up in a race trying to service an interrupt
on IRQ 12 but remains unhandled.
On RELENG_5, I actually catch an interrupt storm. e.g. I attach to sio4
(PUC modem) and
Interrupt storm detected on "irq12: uhci1"; throttling interrupt source
Looking at vmstat -i does indeed show a the rate getting throttled
releng-5-pioneer# vmstat -i
interrupt total rate
irq0: clk 596719 99
irq1: atkbd0 2 0
irq4: sio0 1079 0
irq6: fdc0 1 0
irq8: rtc 763812 127
irq12: uhci1 5825 0
irq13: npx0 1 0
irq14: ata0 38727 6
irq15: vr0 ata1 1984 0
Total 1408150 235
releng-5-pioneer#
where irq12 is the IRQ shared by the modem and the USB port. However,
because all IRQ 12s get throttled, the modem is unusable. e.g. trying to cu
-l /dev/cuaa4 and typing atz takes about 5 seconds.
Is there some way to safely tell the kernel that the PUC device that its
shareable ? We did this perhaps very ugly hack on RELENG_4
@@ -1431,15 +1431,19 @@
rid = 0;
com->irqres = bus_alloc_resource(dev, SYS_RES_IRQ, &rid, 0ul, ~0ul, 1,
- RF_ACTIVE);
+/* RF_ACTIVE); */
+ RF_SHAREABLE);
to /usr/src/sys/isa/sio.c
and at least we can talk to the sio device. However, on RELENG_5 there
does not seem to be the same fix.
My question is this-- Is the root cause the same issue on RELENG_4 and
RELENG_5 ? Are we going about it the best way to fix the problem ? Or is
the underlying problem something else ?
Attached is a dmesg and acpidump
---Mike
--------------------------------------------------------------------
Mike Tancsa, tel +1 519 651 3400
Sentex Communications, mike@sentex.net
Providing Internet since 1994 www.sentex.net
Cambridge, Ontario Canada www.sentex.net/mike
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