1 files changed, 112 insertions, 0 deletions
diff --git a/rust/kernel/sync/completion.rs b/rust/kernel/sync/completion.rs
new file mode 100644
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+++ b/rust/kernel/sync/completion.rs
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+// SPDX-License-Identifier: GPL-2.0
+
+//! Completion support.
+//!
+//! Reference: <https://docs.kernel.org/scheduler/completion.html>
+//!
+//! C header: [`include/linux/completion.h`](srctree/include/linux/completion.h)
+
+use crate::{bindings, prelude::*, types::Opaque};
+
+/// Synchronization primitive to signal when a certain task has been completed.
+///
+/// The [`Completion`] synchronization primitive signals when a certain task has been completed by
+/// waking up other tasks that have been queued up to wait for the [`Completion`] to be completed.
+///
+/// # Examples
+///
+/// ```
+/// use kernel::sync::{Arc, Completion};
+/// use kernel::workqueue::{self, impl_has_work, new_work, Work, WorkItem};
+///
+/// #[pin_data]
+/// struct MyTask {
+///     #[pin]
+///     work: Work<MyTask>,
+///     #[pin]
+///     done: Completion,
+/// }
+///
+/// impl_has_work! {
+///     impl HasWork<Self> for MyTask { self.work }
+/// }
+///
+/// impl MyTask {
+///     fn new() -> Result<Arc<Self>> {
+///         let this = Arc::pin_init(pin_init!(MyTask {
+///             work <- new_work!("MyTask::work"),
+///             done <- Completion::new(),
+///         }), GFP_KERNEL)?;
+///
+///         let _ = workqueue::system().enqueue(this.clone());
+///
+///         Ok(this)
+///     }
+///
+///     fn wait_for_completion(&self) {
+///         self.done.wait_for_completion();
+///
+///         pr_info!("Completion: task complete\n");
+///     }
+/// }
+///
+/// impl WorkItem for MyTask {
+///     type Pointer = Arc<MyTask>;
+///
+///     fn run(this: Arc<MyTask>) {
+///         // process this task
+///         this.done.complete_all();
+///     }
+/// }
+///
+/// let task = MyTask::new()?;
+/// task.wait_for_completion();
+/// # Ok::<(), Error>(())
+/// ```
+#[pin_data]
+pub struct Completion {
+    #[pin]
+    inner: Opaque<bindings::completion>,
+}
+
+// SAFETY: `Completion` is safe to be send to any task.
+unsafe impl Send for Completion {}
+
+// SAFETY: `Completion` is safe to be accessed concurrently.
+unsafe impl Sync for Completion {}
+
+impl Completion {
+    /// Create an initializer for a new [`Completion`].
+    pub fn new() -> impl PinInit<Self> {
+        pin_init!(Self {
+            inner <- Opaque::ffi_init(|slot: *mut bindings::completion| {
+                // SAFETY: `slot` is a valid pointer to an uninitialized `struct completion`.
+                unsafe { bindings::init_completion(slot) };
+            }),
+        })
+    }
+
+    fn as_raw(&self) -> *mut bindings::completion {
+        self.inner.get()
+    }
+
+    /// Signal all tasks waiting on this completion.
+    ///
+    /// This method wakes up all tasks waiting on this completion; after this operation the
+    /// completion is permanently done, i.e. signals all current and future waiters.
+    pub fn complete_all(&self) {
+        // SAFETY: `self.as_raw()` is a pointer to a valid `struct completion`.
+        unsafe { bindings::complete_all(self.as_raw()) };
+    }
+
+    /// Wait for completion of a task.
+    ///
+    /// This method waits for the completion of a task; it is not interruptible and there is no
+    /// timeout.
+    ///
+    /// See also [`Completion::complete_all`].
+    pub fn wait_for_completion(&self) {
+        // SAFETY: `self.as_raw()` is a pointer to a valid `struct completion`.
+        unsafe { bindings::wait_for_completion(self.as_raw()) };
+    }
+}