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;
Date:   Wed, 17 May 2023 20:31:19 +0000
In-Reply-To: <20230517203119.3160435-1-aliceryhl@google.com>
Mime-Version: 1.0
References: <20230517203119.3160435-1-aliceryhl@google.com>
Message-ID: <20230517203119.3160435-8-aliceryhl@google.com>
Subject: [PATCH v1 7/7] rust: workqueue: add `try_spawn` helper method
From:   Alice Ryhl <aliceryhl@google.com>
To:     rust-for-linux@vger.kernel.org
Cc:     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=20Roy=20Baron?=" <bjorn3_gh@protonmail.com>,
        Benno Lossin <benno.lossin@proton.me>,
        Alice Ryhl <aliceryhl@google.com>,
        linux-kernel@vger.kernel.org, patches@lists.linux.dev
Content-Type: text/plain; charset="UTF-8"
Precedence: bulk

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.

Signed-off-by: Alice Ryhl <aliceryhl@google.com>
---
 rust/kernel/workqueue.rs | 40 ++++++++++++++++++++++++++++++++++++++++
 1 file changed, 40 insertions(+)

diff --git a/rust/kernel/workqueue.rs b/rust/kernel/workqueue.rs
index 007005ddcaf0..303b72efd95f 100644
--- a/rust/kernel/workqueue.rs
+++ b/rust/kernel/workqueue.rs
@@ -57,6 +57,42 @@ impl Queue {
             })
         }
     }
+
+    /// 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 + Fn()>(&self, func: T) -> Result {
+        let init = pin_init!(ClosureWork {
+            work <- Work::new(),
+            func: Some(func),
+        });
+
+        self.enqueue(Box::pin_init(init)?);
+        Ok(())
+    }
+}
+
+/// A helper type used in `try_spawn`.
+#[pin_data]
+struct ClosureWork<T> {
+    #[pin]
+    work: Work<Pin<Box<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()> BoxWorkItem for ClosureWork<T> {
+    fn run(mut self: Pin<Box<Self>>) {
+        if let Some(func) = self.as_mut().project().take() {
+            (func)()
+        }
+    }
 }
 
 /// A work item.
@@ -280,6 +316,10 @@ macro_rules! impl_has_work {
     )*};
 }
 
+impl_has_work! {
+    impl<T> HasWork<Pin<Box<Self>>> for ClosureWork<T> { self.work }
+}
+
 /// Declares that [`Arc<Self>`] should implement [`WorkItem`].
 ///
 /// # Examples
-- 
2.40.1.606.ga4b1b128d6-goog