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

Alice Ryhl
2023-06-01T13:56:55Z

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>
---
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>,
--
2.41.0.rc0.172.g3f132b7071-goog