Re: [PATCH 3/4] rust: completion: add complete()

[Maurice Hieronymus <mhi@mailbox.org>]

On Sun, 2026-06-14 at 17:59 +0200, Maurice Hieronymus wrote:
> The initial completion abstraction only added complete_all() and
> wait_for_completion(). complete_all() marks the completion
> permanently
> done, which makes a single Completion unsuitable for signalling the
> same
> event repeatedly: once complete_all() has run, every subsequent
> wait_for_completion() returns immediately without waiting.
> 
> Add complete(), which wakes a single waiter and increments the
> internal
> counter by one. Paired one-to-one with wait_for_completion(), it
> allows
> the same completion to be reused across multiple cycles, e.g. to wait
> for
> consecutive DMA transfers to finish.
> 
> Signed-off-by: Maurice Hieronymus <mhi@mailbox.org>
> ---
>  rust/kernel/sync/completion.rs | 14 ++++++++++++++
>  1 file changed, 14 insertions(+)
> 
> diff --git a/rust/kernel/sync/completion.rs
> b/rust/kernel/sync/completion.rs
> index c50012a940a3..b386b84222f9 100644
> --- a/rust/kernel/sync/completion.rs
> +++ b/rust/kernel/sync/completion.rs
> @@ -90,6 +90,20 @@ fn as_raw(&self) -> *mut bindings::completion {
>          self.inner.get()
>      }
>  
> +    /// Signal one task waiting on this completion.
> +    ///
> +    /// This method wakes up a single task waiting on this
> completion and increments the
> +    /// internal counter by one. If no task is currently waiting,
> the next
> +    /// [`Completion::wait_for_completion`] returns immediately.
> +    ///
> +    /// Unlike [`Completion::complete_all`], the completion is not
> marked permanently done, so a
> +    /// single [`Completion`] paired one-to-one with
> [`Completion::wait_for_completion`] can be
> +    /// reused to signal the same event repeatedly.
Will add #[inline] in V2.
> +    pub fn complete(&self) {
> +        // SAFETY: `self.as_raw()` is a pointer to a valid `struct
> completion`.
> +        unsafe { bindings::complete(self.as_raw()) };
> +    }
> +
>      /// Signal all tasks waiting on this completion.
>      ///
>      /// This method wakes up all tasks waiting on this completion;
> after this operation the