Re: [PATCH v2 0/3] Devres optimization with bound devices

["Alexandre Courbot" <acourbot@nvidia.com>]

On Mon Apr 28, 2025 at 11:00 PM JST, Danilo Krummrich wrote:
> This patch series implements a direct accessor for the data stored within
> a Devres container for cases where we can prove that we own a reference
> to a Device<Bound> (i.e. a bound device) of the same device that was used
> to create the corresponding Devres container.
>
> Usually, when accessing the data stored within a Devres container, it is
> not clear whether the data has been revoked already due to the device
> being unbound and, hence, we have to try whether the access is possible
> and subsequently keep holding the RCU read lock for the duration of the
> access.
>
> However, when we can prove that we hold a reference to Device<Bound>
> matching the device the Devres container has been created with, we can
> guarantee that the device is not unbound for the duration of the
> lifetime of the Device<Bound> reference and, hence, it is not possible
> for the data within the Devres container to be revoked.
>
> Therefore, in this case, we can bypass the atomic check and the RCU read
> lock, which is a great optimization and simplification for drivers.

Thanks, this removes one of my pain points with the way revocable
resources were accessed and will allow to write drivers in a much more
natural way.

FWIW, the series

Reviewed-by: Alexandre Courbot <acourbot@nvidia.com>