On Tue, May 26, 2026 at 05:28:56PM -0400, Lyude Paul wrote:
> Just a temporary holdover to make locking/unlocking the dma_resv lock much
> easier.
>
> Signed-off-by: Lyude Paul <[email protected]>
> Co-authored-by: Alexandre Courbot <[email protected]>
Missing SoB for Alexandre.
> ---
> rust/kernel/drm/gem/shmem.rs | 31 ++++++++++++++++++++++++++++++-
> 1 file changed, 30 insertions(+), 1 deletion(-)
>
> diff --git a/rust/kernel/drm/gem/shmem.rs b/rust/kernel/drm/gem/shmem.rs
> index 116ed0a13eac2..1b24cb1129a8b 100644
> --- a/rust/kernel/drm/gem/shmem.rs
> +++ b/rust/kernel/drm/gem/shmem.rs
> @@ -27,7 +27,10 @@
> Deref,
> DerefMut, //
> },
> - ptr::NonNull,
> + ptr::{
> + self,
> + NonNull, //
> + },
> };
> use gem::{
> BaseObjectPrivate,
> @@ -233,3 +236,29 @@ impl<T: DriverObject> driver::AllocImpl for Object<T> {
> dumb_map_offset: None,
> };
> }
> +
> +/// Private helper-type for holding the `dma_resv` object for a GEM shmem
> object.
> +///
> +/// When this is dropped, the `dma_resv` lock is dropped as well.
> +///
> +// TODO: This should be replace with a WwMutex equivalent once we have such
> bindings in the kernel.
> +struct DmaResvGuard<'a, T: DriverObject>(&'a Object<T>);
Is this missing a NotThreadSafe, or is it safe to unlock on a different
thread than where it was locked?
> +impl<'a, T: DriverObject> DmaResvGuard<'a, T> {
> + #[inline(always)]
> + #[expect(unused)]
> + fn new(obj: &'a Object<T>) -> Self {
> + // SAFETY: This lock is initialized throughout the lifetime of
> `object`.
> + unsafe { bindings::dma_resv_lock(obj.raw_dma_resv(),
> ptr::null_mut()) };
> +
> + Self(obj)
> + }
> +}
> +
> +impl<'a, T: DriverObject> Drop for DmaResvGuard<'a, T> {
> + #[inline(always)]
> + fn drop(&mut self) {
> + // SAFETY: We are releasing the lock grabbed during the creation of
> this object.
> + unsafe { bindings::dma_resv_unlock(self.0.raw_dma_resv()) };
> + }
> +}
> --
> 2.54.0
>
