Re: [PATCH v2 7/8] rust: workqueue: add `try_spawn` helper method

Andreas Hindborg (Samsung)
2023-06-02T14:43:54Z

Alice Ryhl <aliceryhl@google.com> writes:

> This adds a convenience method that lets you spawn a closure for
> execution on a workqueue. This will be the most convenient way to use
> workqueues, but it is fallible because it needs to allocate memory.
>
> Co-developed-by: Gary Guo <gary@garyguo.net>
> Signed-off-by: Gary Guo <gary@garyguo.net>
> Signed-off-by: Alice Ryhl <aliceryhl@google.com>

Reviewed-by: Andreas Hindborg (Samsung) <nmi@metaspace.dk>

> ---
> rust/kernel/workqueue.rs | 43 ++++++++++++++++++++++++++++++++++++++++
> 1 file changed, 43 insertions(+)
>
> diff --git a/rust/kernel/workqueue.rs b/rust/kernel/workqueue.rs
> index f06a2f036d8b..c302e8b8624b 100644
> --- a/rust/kernel/workqueue.rs
> +++ b/rust/kernel/workqueue.rs
> @@ -29,6 +29,7 @@
> //! C header: [`include/linux/workqueue.h`](../../../../include/linux/workqueue.h)
>
> use crate::{bindings, prelude::*, sync::Arc, types::Opaque};
> +use alloc::alloc::AllocError;
> use alloc::boxed::Box;
> use core::marker::{PhantomData, PhantomPinned};
> use core::pin::Pin;
> @@ -87,6 +88,44 @@ pub fn enqueue<W, const ID: u64>(&self, w: W) -> W::EnqueueOutput
> })
> }
> }
> +
> + /// Tries to spawn the given function or closure as a work item.
> + ///
> + /// This method can fail because it allocates memory to store the work item.
> + pub fn try_spawn<T: 'static + Send + FnOnce()>(&self, func: T) -> Result<(), AllocError> {
> + let init = pin_init!(ClosureWork {
> + work <- Work::new(),
> + func: Some(func),
> + });
> +
> + self.enqueue(Box::pin_init(init).map_err(|_| AllocError)?);
> + Ok(())
> + }
> +}
> +
> +/// A helper type used in `try_spawn`.
> +#[pin_data]
> +struct ClosureWork<T> {
> + #[pin]
> + work: Work<ClosureWork<T>>,
> + func: Option<T>,
> +}
> +
> +impl<T> ClosureWork<T> {
> + fn project(self: Pin<&mut Self>) -> &mut Option<T> {
> + // SAFETY: The `func` field is not structurally pinned.
> + unsafe { &mut self.get_unchecked_mut().func }
> + }
> +}
> +
> +impl<T: FnOnce()> WorkItem for ClosureWork<T> {
> + type Pointer = Pin<Box<Self>>;
> +
> + fn run(mut this: Pin<Box<Self>>) {
> + if let Some(func) = this.as_mut().project().take() {
> + (func)()
> + }
> + }
> }
>
> /// A raw work item.
> @@ -325,6 +364,10 @@ unsafe fn raw_get_work(ptr: *mut Self) -> *mut $crate::workqueue::Work<$work_typ
> )*};
> }
>
> +impl_has_work! {
> + impl<T> HasWork<Self> for ClosureWork<T> { self.work }
> +}
> +
> unsafe impl<T, const ID: u64> WorkItemPointer<ID> for Arc<T>
> where
> T: WorkItem<ID, Pointer = Self>,