Re: [driver-core PATCH v8 2/9] driver core: Establish order of operations for device_add and device_del via bitflag

[Dan Williams <dan.j.williams@intel.com>]

On Mon, Dec 10, 2018 at 2:24 PM Alexander Duyck
<alexander.h.duyck@linux.intel.com> wrote:
>
> On Mon, 2018-12-10 at 13:23 -0800, Dan Williams wrote:
> > On Mon, Dec 10, 2018 at 1:15 PM Dan Williams <dan.j.williams@intel.com> wrote:
> > >
> > > On Mon, Dec 10, 2018 at 12:58 PM Alexander Duyck
> > > <alexander.h.duyck@linux.intel.com> wrote:
> >
> > [..]
> > > > Also the context for the two functions seems to be a bit different. In
> > > > the case of __device_attach_driver the device_lock is already held. In
> > > > __driver_attach the lock on the device isn't taken until after a match
> > > > has been found.
> > >
> > > Yes, I was only pattern matching when looking at the context of where
> > > dev->dead is checked in __driver_attach() and wondering why it was
> > > checked outside of __device_attach_driver()
> >
> > ...and now I realize the bigger point of your concern, we need to
> > check dev->dead after acquiring the device_lock otherwise the race is
> > back. We can defer that consolidation, but the larger concern of
> > making it internal to __device_attach_driver() still stands.
>
> I'm still not a fan of moving it into __device_attach_driver. I would
> much rather pull out the dev->driver check and instead place that in
> __device_attach_async_helper.
>
> The __device_attach function as I said took the device_lock and had
> already checked dev->driver. So in the non-async path it shouldn't be
> possible for dev->driver to ever be set anyway.

True.

> In addition
> __device_attach_driver is called once for each driver on a given bus,
> so dropping the test should reduce driver load time since it is one
> less test that has to be performed per driver.

Ok. You can add my Reviewed-by.