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Message-ID: <aIyDQhLePywlGSGQ@google.com>
Date: Fri, 1 Aug 2025 09:05:06 +0000
From: Alice Ryhl <aliceryhl@...gle.com>
To: Boqun Feng <boqun.feng@...il.com>
Cc: rust-for-linux@...r.kernel.org, linux-kernel@...r.kernel.org,
Miguel Ojeda <ojeda@...nel.org>, Alex Gaynor <alex.gaynor@...il.com>, Gary Guo <gary@...yguo.net>,
"Björn Roy Baron" <bjorn3_gh@...tonmail.com>, Benno Lossin <lossin@...nel.org>,
Andreas Hindborg <a.hindborg@...nel.org>, Trevor Gross <tmgross@...ch.edu>,
Danilo Krummrich <dakr@...nel.org>, Tejun Heo <tj@...nel.org>, Tamir Duberstein <tamird@...il.com>,
Hamza Mahfooz <hamzamahfooz@...ux.microsoft.com>, Alban Kurti <kurti@...icto.ai>,
Joel Fernandes <joelagnelf@...dia.com>, "Paul E. McKenney" <paulmck@...nel.org>
Subject: Re: [RFC PATCH] rust: workqueue: Add an example for try_spawn()
On Wed, Jul 30, 2025 at 09:34:39AM -0700, Boqun Feng wrote:
> `try_spawn()` could use an example to demonstrate the usage, and
> arguably it's the most simple usage of workqueue in case someone needs a
> deferred work, so add it.
>
> Cc: Joel Fernandes <joelagnelf@...dia.com>
> Cc: "Paul E. McKenney" <paulmck@...nel.org>
> Signed-off-by: Boqun Feng <boqun.feng@...il.com>
> ---
> Miguel, Alice and Tejun, while I'm at it, should we also rename the
> function to `spawn()` because of the motivation mentioned here [1]?
>
> [1]: https://rust-for-linux.zulipchat.com/#narrow/channel/291566-Library/topic/.60new.60.20or.20.60try_new.60.3F/near/529533317
Renaming sounds good to me.
> Also I find the `{ <clone> || { } }` is really good if I only need to
> clone the Arc for passing to a callback closure, but I'm not sure how
> people feel about it, so criticism is welcome ;-)
It's a neat trick, but I think it risks confusing people. I would
probably not include it in an example like this one.
> rust/kernel/workqueue.rs | 27 +++++++++++++++++++++++++++
> 1 file changed, 27 insertions(+)
>
> diff --git a/rust/kernel/workqueue.rs b/rust/kernel/workqueue.rs
> index b9343d5bc00f..59c1a5e14d12 100644
> --- a/rust/kernel/workqueue.rs
> +++ b/rust/kernel/workqueue.rs
> @@ -331,6 +331,33 @@ pub fn enqueue_delayed<W, const ID: u64>(&self, w: W, delay: Jiffies) -> W::Enqu
> /// 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.
> + ///
> + /// # Examples
> + ///
> + /// ```
> + /// use kernel::{alloc::flags, sync::{Arc, Completion, new_spinlock}, workqueue};
> + ///
> + /// let work_done = Arc::pin_init(Completion::new(), flags::GFP_KERNEL)?;
> + /// let data = Arc::pin_init(new_spinlock!(0), flags::GFP_KERNEL)?;
> + ///
> + /// workqueue::system().try_spawn(
> + /// flags::GFP_KERNEL,
> + /// {
> + /// let work_done = work_done.clone();
> + /// let data = data.clone();
> + /// move || {
> + /// *data.lock() = 42;
> + /// work_done.complete_all();
> + /// }
> + /// }
> + /// )?;
> + ///
> + /// work_done.wait_for_completion();
> + ///
> + /// // `work_done` being completed implies the observation of the write of `data` in the work.
> + /// assert_eq!(*data.lock(), 42);
> + /// # Ok::<(), Error>(())
> + /// ```
> pub fn try_spawn<T: 'static + Send + FnOnce()>(
> &self,
> flags: Flags,
> --
> 2.39.5 (Apple Git-154)
>
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