High IRQ 16 CPU usage (fwd from bugzilla)

[Thorsten Leemhuis <regressions@leemhuis.info>]

Hi, this is your Linux kernel regression tracker speaking.

There is a regression in bugzilla.kernel.org I'd like to add to the
tracking:

#regzbot introduced: 357cf0cdddceea974a7d32668a0df0d9f77055cb
#regzbot from: David Spencer <dspencer577@gmail.com>
#regzbot title: pci: High IRQ 16 CPU usage
#regzbot link: https://bugzilla.kernel.org/show_bug.cgi?id=215546

Quote:

> 
> On 5.15 and 5.16 kernels, if my laptop is plugged in prior to booting or is plugged in at any time after booting I see high CPU usage (80-100% of a core) by IRQ 16, with a constant 15k+ IRQ events per second, whether the system is in use or not. Unplugging the laptop does not make the events stop. If I boot the system without it being plugged in the issue does not occur until I plug it in. Downgrading to 5.14 fixes the issue completely, with only 3 total IRQ 16 interrupts after the system as been running for > 20 minutes. I do not see IRQ16 interrupts increase by using the touch pad, keyboard, or touch screen. I believe I was able to bisect the introduction of the issue to commit 357cf0cdddceea974a7d32668a0df0d9f77055cb, but this was the first time I've done kernel bisects before, so I may be incorrect. I tested with 5.17 RC1 and the issue was still present.
> 
> I've attached dmesg output and the contents of lspci -vvvv, as well as included IRQ 16 info from /proc/interrupts. Please let me know if I can provide anything else.
> 
> /proc/interrupts:
>   16:          0          0    7513443          0          0          0          0          0  IR-IO-APIC   16-fasteoi   idma64.0, i801_smbus, i2c_designware.0

> I think I was incorrect when I said it was in kernel 5.15, when I was bisecting to find the issue the Makefile release information said 5.15-rc2 so I assumed it was in 5.15, but that looks like I was incorrect. I'll test on 5.15 and verify whether it is present there.

> I've confirmed that I do not see the issue on kernel 5.15, only on 5.16.

Ciao, Thorsten (wearing his 'Linux kernel regression tracker' hat)

P.S.: As a Linux kernel regression tracker I'm getting a lot of reports
on my table. I can only look briefly into most of them. Unfortunately
therefore I sometimes will get things wrong or miss something important.
I hope that's not the case here; if you think it is, don't hesitate to
tell me about it in a public reply, that's in everyone's interest.

BTW, I have no personal interest in this issue, which is tracked using
regzbot, my Linux kernel regression tracking bot
(https://linux-regtracking.leemhuis.info/regzbot/). I'm only posting
this mail to get things rolling again and hence don't need to be CC on
all further activities wrt to this regression.

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