Re: smp and irq conflict

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Lapo TIN wrote:
Dear all,
I have a problem with IRQs.

My pc has a CPU PentiumD945 (dual core) and a 2.6.19smp kernel.
I have two video acquisition board (four bt8t8 each) in the only two pci
slots of my motherboard. Thus I have a total of 8 bttv modules that are
working together, and the /proc/interrupts is as follows:
# cat /proc/interrupts
           CPU0       CPU1
  0:      13575          0   IO-APIC-edge      timer
  1:          2          0   IO-APIC-edge      i8042
  4:         11          0   IO-APIC-edge      serial
  8:          1          0   IO-APIC-edge      rtc
  9:          0          0   IO-APIC-fasteoi   acpi
 12:          4          0   IO-APIC-edge      i8042
 14:      22286          0   IO-APIC-edge      ide0
 17:       7073       2097   IO-APIC-fasteoi   uhci_hcd:usb5, eth0
 18:       2525          0   IO-APIC-fasteoi   bttv0, bttv7
 19:       2829          0   IO-APIC-fasteoi   bttv1, bttv4
 20:       2526          0   IO-APIC-fasteoi   bttv2, bttv5
 21:       2226          0   IO-APIC-fasteoi   bttv3, bttv6
 22:          2          0   IO-APIC-fasteoi   ehci_hcd:usb1, uhci_hcd:usb4
 23:         86          0   IO-APIC-fasteoi   uhci_hcd:usb2
 24:          0          0   IO-APIC-fasteoi   uhci_hcd:usb3
NMI:          0          0
LOC:      13484      13502
ERR:          0
MIS:          0
You can see that IRQ18 is shared between bttv0 and bttv7, IRQ19 between
bttv1 and bttv4 and so on.

Sometimes it crashes. It seems a matter of conflict in IRQ.
With only one video board everything is ok, but with two, they shared irq
and something goes wrong... How can I tell to the kernel to not to share the IRQ for these boards ?
I think (I don't know if I'm right) that this could be the problem.

Usually the IRQ routing is hard-wired on the motherboard, so there's no way to avoid the devices sharing IRQs. Unless the driver is badly buggy this should not cause problems anyway.

What kind of video bit rate are you capturing? 8 video capture chips is a pretty heavy load on the PCI bus, maybe something just gets overwhelmed?

Robert Hancock      Saskatoon, SK, Canada
To email, remove "nospam" from hancockr@xxxxxxxxxxxxx
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