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SubjectRe: [driver-core PATCH v4 4/6] driver core: Probe devices asynchronously instead of the driver
On Thu, 2018-10-18 at 12:38 -0700, Alexander Duyck wrote:
> Basically if somebody loads a driver the dev->driver becomes set. If a
> driver is removed it will clear dev->driver and set driver_data to
> 0/NULL. That is what I am using as a mutex to track it in conjunction
> with the device mutex. Basically if somebody attempts to attach a driver
> before we get there we just exit and don't attempt to load this driver.

I don't think that the above matches your code. __device_attach() does not
set the dev->driver pointer before scheduling an asynchronous probe. Only
dev->driver_data gets set before the asynchonous probe is scheduled. Since
driver_detach() only iterates over devices that are in the per-driver klist
it will skip all devices for which an asynchronous probe has been scheduled
but __device_attach_async_helper() has not yet been called. My conclusion
remains that this patch does not prevent a driver pointer to become invalid
concurrently with __device_attach_async_helper() dereferencing the same
driver pointer.


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