On Mon, 2018-12-10 at 13:23 -0800, Dan Williams wrote: > On Mon, Dec 10, 2018 at 1:15 PM Dan Williams <[email protected]> wrote: > > > > On Mon, Dec 10, 2018 at 12:58 PM Alexander Duyck > > <[email protected]> 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. 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.
