[PATCH] rust: workqueue: replace deprecated system_wq with system_{percpu,dfl}_wq

[Alice Ryhl <aliceryhl@google.com>]

From: Danilo Krummrich <dakr@kernel.org>

system_wq is deprecated and triggers a runtime warning:

	[    0.857414] workqueue: work func ...WorkItemPointerKy0_E3runB7_ enqueued on deprecated workqueue. Use system_{percpu|dfl}_wq instead.

Replace system() with system_percpu() and system_dfl(), to match the
previous behavior of the deprecated system() and convert doc examples
and tests to system_dfl().

Fixes: 64d8eae3f895 ("workqueue: Add warnings and fallback if system_{unbound}_wq is used")
Signed-off-by: Danilo Krummrich <dakr@kernel.org>
Reviewed-by: Daniel Almeida <daniel.almeida@collabora.com>
Signed-off-by: Alice Ryhl <aliceryhl@google.com>
---
This patch was previously sent as part of other workqueue series [1][2].
However it's a fix that is independent of those series, so it's sent on
its own here.

[1] https://lore.kernel.org/all/20260726223613.1242940-3-dakr@kernel.org
[2] https://lore.kernel.org/all/20260807165252.3849875-2-dakr@kernel.org

Changes since [2]:
  - Rebase on v7.3-rc7 and also convert the new SpinLockIrq KUnit test,
    which calls workqueue::system() and otherwise fails to build.
  - Add Fixes: tag for the commit that made system_wq warn.
  - Collect Reviewed-by from Daniel.
---
 Documentation/rust/testing.rst                    |  2 +-
 Documentation/translations/zh_CN/rust/testing.rst |  2 +-
 drivers/android/binder/process.rs                 |  4 +--
 rust/kernel/sync/completion.rs                    |  2 +-
 rust/kernel/sync/lock/spinlock.rs                 |  2 +-
 rust/kernel/workqueue.rs                          | 42 +++++++++++++++--------
 6 files changed, 33 insertions(+), 21 deletions(-)

diff --git a/Documentation/rust/testing.rst b/Documentation/rust/testing.rst
index e3943aceceb9..73046523a9a2 100644
--- a/Documentation/rust/testing.rst
+++ b/Documentation/rust/testing.rst
@@ -97,7 +97,7 @@ operator are also supported as usual, e.g.:
 
 	/// ```
 	/// # use kernel::{spawn_work_item, workqueue};
-	/// spawn_work_item!(workqueue::system(), || pr_info!("x\n"))?;
+	/// spawn_work_item!(workqueue::system_dfl(), || pr_info!("x\n"))?;
 	/// # Ok::<(), Error>(())
 	/// ```
 
diff --git a/Documentation/translations/zh_CN/rust/testing.rst b/Documentation/translations/zh_CN/rust/testing.rst
index 6747d0012991..fdd88fa2fe40 100644
--- a/Documentation/translations/zh_CN/rust/testing.rst
+++ b/Documentation/translations/zh_CN/rust/testing.rst
@@ -93,7 +93,7 @@ KUnit 测试即文档测试
 
 	/// ```
 	/// # use kernel::{spawn_work_item, workqueue};
-	/// spawn_work_item!(workqueue::system(), || pr_info!("x\n"))?;
+	/// spawn_work_item!(workqueue::system_dfl(), || pr_info!("x\n"))?;
 	/// # Ok::<(), Error>(())
 	/// ```
 
diff --git a/drivers/android/binder/process.rs b/drivers/android/binder/process.rs
index 5372bfbd93b3..de5bca7f9fc7 100644
--- a/drivers/android/binder/process.rs
+++ b/drivers/android/binder/process.rs
@@ -1728,7 +1728,7 @@ pub(crate) fn release(this: Arc<Process>, _file: &File) {
         if should_schedule {
             // Ignore failures to schedule to the workqueue. Those just mean that we're already
             // scheduled for execution.
-            let _ = workqueue::system().enqueue(this);
+            let _ = workqueue::system_percpu().enqueue(this);
         }
 
         drop(binderfs_file);
@@ -1745,7 +1745,7 @@ pub(crate) fn flush(this: ArcBorrow<'_, Process>) -> Result {
         if should_schedule {
             // Ignore failures to schedule to the workqueue. Those just mean that we're already
             // scheduled for execution.
-            let _ = workqueue::system().enqueue(Arc::from(this));
+            let _ = workqueue::system_percpu().enqueue(Arc::from(this));
         }
         Ok(())
     }
diff --git a/rust/kernel/sync/completion.rs b/rust/kernel/sync/completion.rs
index 35ff049ff078..1771bfc0ade2 100644
--- a/rust/kernel/sync/completion.rs
+++ b/rust/kernel/sync/completion.rs
@@ -38,7 +38,7 @@
 ///             done <- Completion::new(),
 ///         }), GFP_KERNEL)?;
 ///
-///         let _ = workqueue::system().enqueue(this.clone());
+///         let _ = workqueue::system_dfl().enqueue(this.clone());
 ///
 ///         Ok(this)
 ///     }
diff --git a/rust/kernel/sync/lock/spinlock.rs b/rust/kernel/sync/lock/spinlock.rs
index aafc80125f59..92ad133262b6 100644
--- a/rust/kernel/sync/lock/spinlock.rs
+++ b/rust/kernel/sync/lock/spinlock.rs
@@ -450,7 +450,7 @@ fn run(this: Arc<Self>) {
     fn spinlock_irq_condvar() -> Result {
         let testdata = Test::new()?;
 
-        let _ = workqueue::system().enqueue(testdata.clone());
+        let _ = workqueue::system_dfl().enqueue(testdata.clone());
 
         // Let the updater know when we're ready to wait
         let mut state = testdata.state.lock();
diff --git a/rust/kernel/workqueue.rs b/rust/kernel/workqueue.rs
index 7e253b6f299c..7bc07ccd1ebb 100644
--- a/rust/kernel/workqueue.rs
+++ b/rust/kernel/workqueue.rs
@@ -67,7 +67,7 @@
 //! /// This method will enqueue the struct for execution on the system workqueue, where its value
 //! /// will be printed.
 //! fn print_later(val: Arc<MyStruct>) {
-//!     let _ = workqueue::system().enqueue(val);
+//!     let _ = workqueue::system_dfl().enqueue(val);
 //! }
 //! # print_later(MyStruct::new(42).unwrap());
 //! ```
@@ -121,11 +121,11 @@
 //! }
 //!
 //! fn print_1_later(val: Arc<MyStruct>) {
-//!     let _ = workqueue::system().enqueue::<Arc<MyStruct>, 1>(val);
+//!     let _ = workqueue::system_dfl().enqueue::<Arc<MyStruct>, 1>(val);
 //! }
 //!
 //! fn print_2_later(val: Arc<MyStruct>) {
-//!     let _ = workqueue::system().enqueue::<Arc<MyStruct>, 2>(val);
+//!     let _ = workqueue::system_dfl().enqueue::<Arc<MyStruct>, 2>(val);
 //! }
 //! # print_1_later(MyStruct::new(24, 25).unwrap());
 //! # print_2_later(MyStruct::new(41, 42).unwrap());
@@ -171,13 +171,13 @@
 //! /// This method will enqueue the struct for execution on the system workqueue, where its value
 //! /// will be printed 12 jiffies later.
 //! fn print_later(val: Arc<MyStruct>) {
-//!     let _ = workqueue::system().enqueue_delayed(val, 12);
+//!     let _ = workqueue::system_dfl().enqueue_delayed(val, 12);
 //! }
 //!
 //! /// It is also possible to use the ordinary `enqueue` method together with `DelayedWork`. This
 //! /// is equivalent to calling `enqueue_delayed` with a delay of zero.
 //! fn print_now(val: Arc<MyStruct>) {
-//!     let _ = workqueue::system().enqueue(val);
+//!     let _ = workqueue::system_dfl().enqueue(val);
 //! }
 //! # print_later(MyStruct::new(42).unwrap());
 //! # print_now(MyStruct::new(42).unwrap());
@@ -1024,20 +1024,32 @@ unsafe impl<T, const ID: u64> RawDelayedWorkItem<ID> for ARef<T>
 {
 }
 
-/// Returns the system work queue (`system_wq`).
+/// Returns the system per-cpu work queue (`system_percpu_wq`).
 ///
 /// It is the one used by `schedule[_delayed]_work[_on]()`. Multi-CPU multi-threaded. There are
 /// users which expect relatively short queue flush time.
 ///
 /// Callers shouldn't queue work items which can run for too long.
-pub fn system() -> &'static Queue {
-    // SAFETY: `system_wq` is a C global, always available.
-    unsafe { Queue::from_raw(bindings::system_wq) }
+#[inline]
+pub fn system_percpu() -> &'static Queue {
+    // SAFETY: `system_percpu_wq` is a C global, always available.
+    unsafe { Queue::from_raw(bindings::system_percpu_wq) }
+}
+
+/// Returns the system default (unbound) work queue (`system_dfl_wq`).
+///
+/// Workers are not bound to any specific CPU, not concurrency managed, and all queued work items
+/// are executed immediately as long as `max_active` limit is not reached and resources are
+/// available.
+#[inline]
+pub fn system_dfl() -> &'static Queue {
+    // SAFETY: `system_dfl_wq` is a C global, always available.
+    unsafe { Queue::from_raw(bindings::system_dfl_wq) }
 }
 
 /// Returns the system high-priority work queue (`system_highpri_wq`).
 ///
-/// It is similar to the one returned by [`system`] but for work items which require higher
+/// It is similar to the one returned by [`system_percpu`] but for work items which require higher
 /// scheduling priority.
 pub fn system_highpri() -> &'static Queue {
     // SAFETY: `system_highpri_wq` is a C global, always available.
@@ -1046,8 +1058,8 @@ pub fn system_highpri() -> &'static Queue {
 
 /// Returns the system work queue for potentially long-running work items (`system_long_wq`).
 ///
-/// It is similar to the one returned by [`system`] but may host long running work items. Queue
-/// flushing might take relatively long.
+/// It is similar to the one returned by [`system_percpu`] but may host long running work items.
+/// Queue flushing might take relatively long.
 pub fn system_long() -> &'static Queue {
     // SAFETY: `system_long_wq` is a C global, always available.
     unsafe { Queue::from_raw(bindings::system_long_wq) }
@@ -1065,7 +1077,7 @@ pub fn system_unbound() -> &'static Queue {
 
 /// Returns the system freezable work queue (`system_freezable_wq`).
 ///
-/// It is equivalent to the one returned by [`system`] except that it's freezable.
+/// It is equivalent to the one returned by [`system_percpu`] except that it's freezable.
 ///
 /// A freezable workqueue participates in the freeze phase of the system suspend operations. Work
 /// items on the workqueue are drained and no new work item starts execution until thawed.
@@ -1078,7 +1090,7 @@ pub fn system_freezable() -> &'static Queue {
 ///
 /// It is inclined towards saving power and is converted to "unbound" variants if the
 /// `workqueue.power_efficient` kernel parameter is specified; otherwise, it is similar to the one
-/// returned by [`system`].
+/// returned by [`system_percpu`].
 pub fn system_power_efficient() -> &'static Queue {
     // SAFETY: `system_power_efficient_wq` is a C global, always available.
     unsafe { Queue::from_raw(bindings::system_power_efficient_wq) }
@@ -1097,7 +1109,7 @@ pub fn system_freezable_power_efficient() -> &'static Queue {
 
 /// Returns the system bottom halves work queue (`system_bh_wq`).
 ///
-/// It is similar to the one returned by [`system`] but for work items which
+/// It is similar to the one returned by [`system_percpu`] but for work items which
 /// need to run from a softirq context.
 pub fn system_bh() -> &'static Queue {
     // SAFETY: `system_bh_wq` is a C global, always available.

---
base-commit: 24a19b953e2a3d0ea5a8c4951a0ab8f32720c907
change-id: 20261013-rust-workqueue-system-fix-5f9020c90f27

Best regards,
-- 
Alice Ryhl <aliceryhl@google.com>