Re: [GIT PULL] Driver core changes for 7.0-rc1

["Uwe Kleine-König" <u.kleine-koenig@baylibre.com>]

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Hello,

On Sat, Feb 28, 2026 at 11:44:25PM -0800, Linus Torvalds wrote:
> On Wed, 11 Feb 2026 at 15:04, Danilo Krummrich <dakr@kernel.org> wrote:
> >
> > Driver core changes for 7.0-rc1
> >
> > - Bus:
> >   - Ensure bus->match() is consistently called with the device lock held
> 
> So I'm coming back to this, because it turns out this sounds like a
> horrible mistake in the end.
> 
> You document it as being about consistent locking, but it appears this
> change is what made the "firewire oops at driver attach" turn an oops
> into just a silently dead machine.
> 
> In other words, it makes fragile drivers go from "you get an oops" to
> something much worse. The oops becomes unrecoverable - with typically
> a black screen at boot - because the probe is holding a lock that then
> makes everything else come to a grinding halt when the driver fails.
> 
> And yes, this obviously only happens for buggy driver and doesn't
> matter for _correct_ code, but about half of the kernel code is
> drivers, and that half of the kernel code is also the typically the
> most badly tested and often questionably implemented half.

I have a machine here (stm32mp135f-dk, ARCH=arm) that fails to boot with
dc23806a7c47 ("driver core: enforce device_lock for
driver_match_device()"), but doesn't oops on dc23806a7c47^.
(Fails to boot = no kernel messages on console.)

I didn't try to debug that yet, but I wonder if that is an understood
problem of said commit. I know that the commit was reverted in the
meantime (and the machine boots fine on 9de68394a615 ("Revert "driver
core: enforce device_lock for driver_match_device()""), but does that
mean that there is a driver involved that somehow violates driver core
assumptions and should be fixed even without the consistent locking?
Hints about how to approach the issue (if there is any) welcome.

Best regards
Uwe

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