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

Linus Torvalds
2026-03-01T07:44:44Z

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.

No, not all drivers a bad, but there are a lot of drivers, and some of
them have problems.

So if a driver problem causes problems for the whole machine, the
driver core design is bad.

I really think this should be re-thought. Perhaps just reverted
outright. Instead of saying

"This inconsistency means that
bus match() callbacks are not guaranteed to be called with the lock
held"

as if it's automatically a bad thing, just don't depend on the device
match having to be called with a lock held if that lock has this
problem.

It's not clear why anybody should *care* about the lock at driver
attach time, when nothing else can access the device that hasn't been
brought up yet.

Put another way: the downsides seem worse than the upsides.
"Consistency" is not an upside if it causes problems.

Linus