SIO Interrupt storms and unhanded interrupts

[John Baldwin]

On Wednesday 08 September 2004 07:25 pm, Mike Tancsa wrote:
> 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

You can do a similar hack to puc/sio in 5.x, but you also need to remove the 
'INTR_FAST' flag to bus_setup_intr() for it to work.

-- 
John Baldwin <jhb at FreeBSD.org>  <><  http://www.FreeBSD.org/~jhb/
"Power Users Use the Power to Serve"  =  http://www.FreeBSD.org