Re: Need help fixing an unhandled irq

On Tue, Apr 21, 2015 at 8:49 PM, Kynn Jones <kynnjo@gmail.com> wrote:

Looking at the output from `/proc/interrupts`

                 CPU0       CPU1       CPU2       CPU3
        0:         53          0          0          0 IR-IO-APIC-edge      timer
        1:          3          0          0          0 IR-IO-APIC-edge      i8042
        8:          1          0          0          0 IR-IO-APIC-edge      rtc0
        9:          0          0          0          0 IR-IO-APIC-fasteoi   acpi
       12:          4          0          0          0 IR-IO-APIC-edge      i8042
    * 16:      29065          0          0          0 IR-IO-APIC-fasteoi   ehci_hcd:usb1, snd_hda_intel
       23:      37100          0          0          0 IR-IO-APIC-fasteoi   ehci_hcd:usb2
       40:          0          0          0          0 DMAR_MSI-edge      dmar0
       41:          0          0          0          0 DMAR_MSI-edge      dmar1
       42:      11425          0          0          0 IR-PCI-MSI-edge      eth0
       43:      53906          0          0          0 IR-PCI-MSI-edge      ahci
       44:         60          0          0          0 IR-PCI-MSI-edge      xhci_hcd
    * 45:        235          0          0          0 IR-PCI-MSI-edge      snd_hda_intel
      NMI:        102         60         51         95   Non-maskable interrupts
      LOC:      67413      40257      57679      43949   Local timer interrupts
      SPU:          0          0          0          0   Spurious interrupts
      PMI:        102         60         51         95   Performance monitoring interrupts
      IWI:          0          0          0          0   IRQ work interrupts
      RES:     150105     180510     183193     156750   Rescheduling interrupts
      CAL:        396        638        603        655   Function call interrupts
      TLB:       2362       3182       3646       3919   TLB shootdowns
      TRM:          0          0          0          0   Thermal event interrupts
      THR:          0          0          0          0   Threshold APIC interrupts
      MCE:          0          0          0          0   Machine check exceptions
      MCP:         13         13         13         13   Machine check polls
      ERR:          0
      MIS:          0

...I see that for irq 16 there are two entries in the last column: ehci_hcd:usb1 and snd_hda_intel, and that there is another snd_hda_intel entry for irq 45. (See the rows indicated by the added asterisks.)

(FWIW, the system's sound is fine AFAICT.)

I see a glimmer of hope in this (apparent?) redundancy. My thinking goes like this: (1) *maybe* the snd_hda_intel listed for interrupt 16 is what's responsible for the unhandled interrupt, and (2) *maybe* this snd_hda_intel can be disabled altogether, in light of the snd_hda_intel listed for interrupt 45? But I really don't know what I'm talking about. More importantly, even if these wishful guesses turn out to be correct, I don't know how to go about disabling the snd_hda_intel associated with irq 16.

OK, I found a way to turn off one of the two snd_hda_intel, but it turned out to be the one on IRQ 45. (In any case, doing this did not solve the problem.)

The method I used was

1. find the prefix of the audio device(s) in the output of lspci

2. search for a path under /sys/devices with this prefix in the basename

3. add a line of the form

echo 1 > /path/found/in/previous/step/remove

When did step (1) I found two candidate prefixes 00:03.0 and 00.1b.0, from the lines

00:03.0 Audio device: Intel Corporation Haswell HD Audio Controller (rev 06)
00:1b.0 Audio device: Intel Corporation Lynx Point High Definition Audio Controller (rev 04)

but in step (2) I was able to find only one matching path, namely

/sys/devices/pci0000:00/0000:00:1b.0

I went ahead and added the line

echo 1 > /sys/devices/pci0000:00/0000:00:1b.0/remove

to /etc/rc.local, and rebooted. Then I saw that the line

45: 235 0 0 0 IR-PCI-MSI-edge snd_hda_intel

was missing from the listing from /proc/interrupts, but the line

16: 18185 0 0 0 IR-IO-APIC-fasteoi ehci_hcd:usb1, snd_hda_intel

was still there. Not surprisingly (given that the situation for IRQ 16 appears unchanged), the original problem with the lagging mouse persists.

But at least now I've narrowed my question to: how to turn off

00:03.0 Audio device: Intel Corporation Haswell HD Audio Controller (rev 06)

?

Does anyone have any ideas?

Thanks in advance!