On Mon, 2018-12-10 at 13:23 -0800, Dan Williams wrote:
On Mon, Dec 10, 2018 at 1:15 PM Dan Williams [off-list ref] wrote:
quoted
On Mon, Dec 10, 2018 at 12:58 PM Alexander Duyck
[off-list ref] wrote:
[..]
quoted
quoted
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.