Re: loading firmware while usermodehelper disabled.

Alan Stern
2012-01-01T16:17:55Z

On Sun, 1 Jan 2012, Oliver Neukum wrote:

> Am Sonntag, 1. Januar 2012, 03:21:45 schrieb Alan Stern:
> > On Sat, 31 Dec 2011, Oliver Neukum wrote:
>
> > > We are definitely going through do_unbind_rebind(). But I don't think
> > > it matters why we got there. We seem to be calling probe() too early.
> > > And we need to guarantee that a driver can request firmware in probe()
> > >
> > > So something has changed in the resume code path further up.
> >
> > For at least a year and a half, it has been true that rebinding takes
>
> Yes, so I don't understand why we haven't been hitting this issue
> all that time.

Perhaps if Matthew compared logs from an old and a new system with
appropriate debugging options configured, something might show up.

> > place during the complete phase of system resume. Clearly that is too
> > early to load firmware. When do you think we should do it instead?
>
> I think we ought to delay until right after user space is unfrozen.
> The devices are gone anyway, so we lose nothing but have the ability
> to call helpers.

That's true. But doing it will be a nuisance. The nice thing about
the current situation is that the driver core automatically iterates
over all interfaces.

> > And how should we keep track of which interfaces need rebinding?
>
> I guess this calls for a brute force approach. We can kick khubd and have
> it walk all busses checking for needs_binding.

Ugh. At a minimum, let's use a different process, not khubd.

As Linus pointed out, the real problem here is the firmware loader.
The way it is now, a driver can't always depend on the data being
available, even during a normal boot. It ought to use an asynchronous
approach; then none of these problems would arise.

Alan Stern