Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20;
References: <20230601134946.3887870-1-aliceryhl@google.com>
 <20230601134946.3887870-8-aliceryhl@google.com>
User-agent: mu4e 1.10.3; emacs 28.2.50
From:   "Andreas Hindborg (Samsung)" <nmi@metaspace.dk>
To:     Alice Ryhl <aliceryhl@google.com>
Cc:     rust-for-linux@vger.kernel.org, Miguel Ojeda <ojeda@kernel.org>,
        Wedson Almeida Filho <wedsonaf@gmail.com>,
        Tejun Heo <tj@kernel.org>,
        Lai Jiangshan <jiangshanlai@gmail.com>,
        Alex Gaynor <alex.gaynor@gmail.com>,
        Boqun Feng <boqun.feng@gmail.com>, Gary Guo <gary@garyguo.net>,
        =?utf-8?Q?Bj=C3=B6rn?= Roy Baron <bjorn3_gh@protonmail.com>,
        Benno Lossin <benno.lossin@proton.me>,
        linux-kernel@vger.kernel.org, patches@lists.linux.dev
Subject: Re: [PATCH v2 7/8] rust: workqueue: add `try_spawn` helper method
Date:   Fri, 02 Jun 2023 16:43:33 +0200
In-reply-to: <20230601134946.3887870-8-aliceryhl@google.com>
Message-ID: <87bkhx2acd.fsf@metaspace.dk>
MIME-Version: 1.0
Content-Type: text/plain
Precedence: bulk


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>,