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From 1b56e765bf8990f1f60e124926c11fc4ac63d752 Mon Sep 17 00:00:00 2001
From: Danilo Krummrich <dakr@kernel.org>
Date: Thu, 12 Jun 2025 14:17:13 +0200
Subject: rust: completion: implement initial abstraction
From: Danilo Krummrich <dakr@kernel.org>
commit 1b56e765bf8990f1f60e124926c11fc4ac63d752 upstream.
Implement a minimal abstraction for the completion synchronization
primitive.
This initial abstraction only adds complete_all() and
wait_for_completion(), since that is what is required for the subsequent
Devres patch.
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Juri Lelli <juri.lelli@redhat.com>
Cc: Vincent Guittot <vincent.guittot@linaro.org>
Cc: Dietmar Eggemann <dietmar.eggemann@arm.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Ben Segall <bsegall@google.com>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Valentin Schneider <vschneid@redhat.com>
Reviewed-by: Alice Ryhl <aliceryhl@google.com>
Reviewed-by: Boqun Feng <boqun.feng@gmail.com>
Reviewed-by: Benno Lossin <lossin@kernel.org>
Acked-by: Miguel Ojeda <ojeda@kernel.org>
Link: https://lore.kernel.org/r/20250612121817.1621-2-dakr@kernel.org
Signed-off-by: Danilo Krummrich <dakr@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
rust/bindings/bindings_helper.h | 1
rust/helpers/completion.c | 8 ++
rust/helpers/helpers.c | 1
rust/kernel/sync.rs | 2
rust/kernel/sync/completion.rs | 112 ++++++++++++++++++++++++++++++++++++++++
5 files changed, 124 insertions(+)
create mode 100644 rust/helpers/completion.c
create mode 100644 rust/kernel/sync/completion.rs
--- a/rust/bindings/bindings_helper.h
+++ b/rust/bindings/bindings_helper.h
@@ -10,6 +10,7 @@
#include <linux/blk-mq.h>
#include <linux/blk_types.h>
#include <linux/blkdev.h>
+#include <linux/completion.h>
#include <linux/cpumask.h>
#include <linux/cred.h>
#include <linux/device/faux.h>
--- /dev/null
+++ b/rust/helpers/completion.c
@@ -0,0 +1,8 @@
+// SPDX-License-Identifier: GPL-2.0
+
+#include <linux/completion.h>
+
+void rust_helper_init_completion(struct completion *x)
+{
+ init_completion(x);
+}
--- a/rust/helpers/helpers.c
+++ b/rust/helpers/helpers.c
@@ -11,6 +11,7 @@
#include "bug.c"
#include "build_assert.c"
#include "build_bug.c"
+#include "completion.c"
#include "cpumask.c"
#include "cred.c"
#include "device.c"
--- a/rust/kernel/sync.rs
+++ b/rust/kernel/sync.rs
@@ -10,6 +10,7 @@ use crate::types::Opaque;
use pin_init;
mod arc;
+pub mod completion;
mod condvar;
pub mod lock;
mod locked_by;
@@ -17,6 +18,7 @@ pub mod poll;
pub mod rcu;
pub use arc::{Arc, ArcBorrow, UniqueArc};
+pub use completion::Completion;
pub use condvar::{new_condvar, CondVar, CondVarTimeoutResult};
pub use lock::global::{global_lock, GlobalGuard, GlobalLock, GlobalLockBackend, GlobalLockedBy};
pub use lock::mutex::{new_mutex, Mutex, MutexGuard};
--- /dev/null
+++ b/rust/kernel/sync/completion.rs
@@ -0,0 +1,112 @@
+// 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()) };
+ }
+}
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