Re: git: 477c594d9063 - main - kobj: allow multiple inheritance with per-class softc

On 18.09.2026 0:15, Kristof Provost wrote:
> On 11 Sep 2026, at 16:09, Michal Meloun wrote:
> 
>     The branch main has been updated by mmel:
> 
>     URL: https://cgit.FreeBSD.org/src/commit/?
>     id=477c594d906328e210c30cf2c21d983152f21de3 <https://
>     cgit.FreeBSD.org/src/commit/?
>     id=477c594d906328e210c30cf2c21d983152f21de3>
> 
>     commit 477c594d906328e210c30cf2c21d983152f21de3
>     Author: Michal Meloun mmel@FreeBSD.org <mailto:mmel@FreeBSD.org>
>     AuthorDate: 2026-09-11 11:47:30 +0000
>     Commit: Michal Meloun mmel@FreeBSD.org <mailto:mmel@FreeBSD.org>
>     CommitDate: 2026-09-11 14:09:36 +0000
> 
>     |kobj: allow multiple inheritance with per-class softc Add support
>     for hierarchical softc layout so that a leaf class and each of its
>     base classes owns a private softc region inside a single allocation.
>     device_get_softc_class(dev, cls) returns a pointer to the softc that
>     belongs to the requested class. The classic device_get_softc() still
>     returns the leaf softc and remains fully compatible with existing
>     drivers. Existing drivers are unaffected; they simply obtain a
>     slightly larger softc block when they inherit from base classes. |
> 
> For some reason this commit causes my machine (Dell T640) to fail to boot.
> 
> It doesn’t panic, but it seems to be very slow during boot, and seems to 
> remain stuck around when it’d start userspace. (Freezing just before | 
> Trying to mount root from zfs:zroot/ROOT/16.0-CURRENT-20260917.222603|)
> 
> I don’t even begin to understand how that’d be related to this commit, 
> but it’s very reproducible.
> 
> Do you have any suggestions for how to begin to debug this?
> 
> Thanks,
> Kristof
> 
I also don't see how this change could have directly caused the 
described failure.
Could you generate a backtrace from the hung state? Ideally, generate 
more than one to see where the kernel is livelocked.

Also, can you, for test, replace
"size = kobj_total_data_size(driver);"
with
"size = driver->size;"
at
https://cgit.freebsd.org/src/tree/sys/kern/subr_bus.c#n2503 ?

Thanks,
Michal