Re: Regression causes a hang on boot with a Comtrol PCI card

Bjorn Helgaas
2019-03-13T23:21:16Z

Hi Jesse,

On Wed, Mar 13, 2019 at 11:50:07AM -0500, Jesse Hathaway wrote:
> Two regressions cause Linux to hang on boot when a Comtrol PCI card
> is present.
>
> If I revert the following two commits, I can boot again and the card
> operates without issue:
>
> 1302fcf0d03e (refs/bisect/bad) PCI: Configure *all* devices, not just
> hot-added ones
> 1c3c5eab1715 sched/core: Enable might_sleep() and smp_processor_id()
> checks early

I'm very sorry about the regression, but thank you very much for
narrowing it down and reporting it!

How did you narrow it down to *two* commits, and do you have to revert
both of them to avoid the hang? Usually a bisection identifies a
single commit, and the two you mention aren't related.

> ; lspci -vs 82:00.0
> 82:00.0 Multiport serial controller: Comtrol Corporation Device 0061
> Subsystem: Comtrol Corporation Device 0061
> Flags: 66MHz, medium devsel, IRQ 35, NUMA node 1
> Memory at c8004000 (32-bit, non-prefetchable) [size=4K]
> Memory at c8000000 (32-bit, non-prefetchable) [size=16K]
> Capabilities: [40] Hot-plug capable
> Capabilities: [48] Power Management version 2
> Kernel driver in use: rp2
> Kernel modules: rp2
>
> Is it possible that the problem is that the card claims to support
> Hot-plug, but does not?
>
> I would love to help fix this issue, please let me know what other
> information would be helpful to provide.

Can you collect a complete dmesg log (with a working kernel) and
output of "sudo lspci -vvxxx"? You can open a bug report at
https://bugzilla.kernel.org, attach the logs there, and respond here
with the URL.

Where does the hang happen? Is it when we configure the Comtrol card?

Bjorn