[PATCH v4 0/3] rust: workqueue: add safe cancellation and status methods

[PATCH v4 0/3] rust: workqueue: add safe cancellation and status methods

[Aakash Bollineni via B4 Relay]

This is the fourth version of the patch series for modernizing the Linux
kernel Rust workqueue infrastructure.

Changes in v4:
- Fixed rustfmt and formatting errors in samples/rust/rust_workqueue_test.rs
  reported by the kernel test robot.
- Added Reported-by and Closes tags to the third patch for robot tracking.
- Improved the commit structure to cleanly separate API changes from tests.
- Link to v3: https://lore.kernel.org/r/20260403-workqueue-v3-final-v3-0-6ffc3950d804@multicorewareinc.com

Changes in v3:
- Fixed a critical initialization bug in the DelayedWork C-helper where
  the timer function was not correctly registered, causing KUnit crashes.
- Consolidated Arc refcount inspection into a shared `arc_count` helper
  in `rust/kernel/workqueue.rs` (gated by CONFIG_KUNIT).
- Updated internal KUnit tests and sample module to use the shared helper.
- Split the sample test's `TestItem` into `TestWorkItem` and
  `TestDelayedWorkItem` for clearer trait dispatch and safety.
- Integrated the sample stress test into the kernel build system via
  the SAMPLES_RUST Kconfig.
- Improved documentation and safety comments based on feedback from
  Onur and Miguel Ojeda.

Aakash Bollineni (3):
  rust: helpers: add workqueue helpers
  rust: workqueue: add safe cancellation and status methods
  rust: workqueue: add KUnit and sample stress tests

To: Miguel Ojeda <ojeda@kernel.org>
To: Alex Gaynor <alex.gaynor@gmail.com>
To: Wedson Almeida Filho <wedsonaf@gmail.com>
To: Boqun Feng <boqun.feng@gmail.com>
To: Gary Guo <gary@garyguo.net>
To: Björn Roy Baron <bjorn.roy.baron@gmail.com>
To: Benno Lossin <benno.lossin@proton.me>
To: Andreas Hindborg <a.hindborg@samsung.com>
To: Alice Ryhl <aliceryhl@google.com>
To: Tejun Heo <tj@kernel.org>
To: Lai Jiangshan <jiangshanlai@gmail.com>
Cc: rust-for-linux@vger.kernel.org
Cc: linux-kernel@vger.kernel.org

Signed-off-by: Aakash Bollineni <aakash.bollineni@multicorewareinc.com>
---
Aakash Bollineni (3):
      rust: helpers: add workqueue helpers
      rust: workqueue: add safe cancellation and status methods
      rust: workqueue: add KUnit and sample stress tests

 rust/helpers/workqueue.c            |  32 +++
 rust/kernel/workqueue.rs            | 463 +++++++++++++++++++++++++++++++++---
 samples/rust/Kconfig                |  10 +
 samples/rust/Makefile               |   2 +
 samples/rust/rust_workqueue_test.rs | 192 +++++++++++++++
 5 files changed, 664 insertions(+), 35 deletions(-)
---
base-commit: bf074eb6891be799174ff42e0051492681fdc045
change-id: 20260403-workqueue-v3-final-fa406defb67c

Best regards,
-- 
Aakash Bollineni <aakash.bollineni@multicorewareinc.com>

[PATCH v4 1/3] rust: helpers: add workqueue helpers

[Aakash Bollineni via B4 Relay]

From: Aakash Bollineni <aakash.bollineni@multicorewareinc.com>

Add C-helpers to bridge the Rust workqueue abstraction with the
kernel's C workqueue macros. These helpers wrap core workqueue
functions that are either inline or macros in C, making them
accessible to Rust FFI.
New wrappers:
- rust_helper_work_pending(): Wraps work_pending().
- rust_helper_cancel_work_sync(): Wraps cancel_work_sync().
- rust_helper_cancel_delayed_work_sync(): Wraps cancel_delayed_work_sync().
- rust_helper_init_delayed_work(): Performs robust initialization of
  a delayed_work structure, ensuring the correct timer function
  (delayed_work_timer_fn) and lockdep maps are initialized using
  standard kernel macros.
These helpers are essential for supporting safe cancellation and
correct DelayedWork lifecycle management in the Rust workqueue API.

Signed-off-by: Aakash Bollineni <aakash.bollineni@multicorewareinc.com>
---
 rust/helpers/workqueue.c | 32 ++++++++++++++++++++++++++++++++
 1 file changed, 32 insertions(+)

diff --git a/rust/helpers/workqueue.c b/rust/helpers/workqueue.c
index ce1c3a5b2150..85a6c0b9e4d5 100644
--- a/rust/helpers/workqueue.c
+++ b/rust/helpers/workqueue.c
@@ -14,3 +14,35 @@ __rust_helper void rust_helper_init_work_with_key(struct work_struct *work,
 	INIT_LIST_HEAD(&work->entry);
 	work->func = func;
 }
+
+__rust_helper bool rust_helper_work_pending(struct work_struct *work)
+{
+	return work_pending(work);
+}
+
+__rust_helper bool rust_helper_cancel_work_sync(struct work_struct *work)
+{
+	return cancel_work_sync(work);
+}
+
+__rust_helper bool rust_helper_cancel_delayed_work_sync(struct delayed_work *dwork)
+{
+	return cancel_delayed_work_sync(dwork);
+}
+
+__rust_helper void rust_helper_init_delayed_work(struct delayed_work *dwork,
+						 work_func_t func,
+						 const char *name,
+						 struct lock_class_key *key,
+						 const char *tname,
+						 struct lock_class_key *tkey)
+{
+	INIT_DELAYED_WORK(dwork, func);
+	lockdep_init_map(&dwork->work.lockdep_map, name, key, 0);
+	timer_init_key(&dwork->timer, dwork->timer.function, TIMER_IRQSAFE, tname, tkey);
+}
+
+__rust_helper void *rust_helper_get_dwork_timer_fn(void)
+{
+	return (void *)delayed_work_timer_fn;
+}

-- 
2.43.0

Re: [PATCH v4 1/3] rust: helpers: add workqueue helpers

[Gary Guo]

On Tue Apr 7, 2026 at 11:37 AM BST, Aakash Bollineni via B4 Relay wrote:
> From: Aakash Bollineni <aakash.bollineni@multicorewareinc.com>
>
> Add C-helpers to bridge the Rust workqueue abstraction with the
> kernel's C workqueue macros. These helpers wrap core workqueue
> functions that are either inline or macros in C, making them
> accessible to Rust FFI.
> New wrappers:
> - rust_helper_work_pending(): Wraps work_pending().
> - rust_helper_cancel_work_sync(): Wraps cancel_work_sync().
> - rust_helper_cancel_delayed_work_sync(): Wraps cancel_delayed_work_sync().

These lines are of very low information density. Just state what's wrapped.

> - rust_helper_init_delayed_work(): Performs robust initialization of
>   a delayed_work structure, ensuring the correct timer function
>   (delayed_work_timer_fn) and lockdep maps are initialized using
>   standard kernel macros.
> These helpers are essential for supporting safe cancellation and
> correct DelayedWork lifecycle management in the Rust workqueue API.
>
> Signed-off-by: Aakash Bollineni <aakash.bollineni@multicorewareinc.com>
> ---
>  rust/helpers/workqueue.c | 32 ++++++++++++++++++++++++++++++++
>  1 file changed, 32 insertions(+)
>
> diff --git a/rust/helpers/workqueue.c b/rust/helpers/workqueue.c
> index ce1c3a5b2150..85a6c0b9e4d5 100644
> --- a/rust/helpers/workqueue.c
> +++ b/rust/helpers/workqueue.c
> @@ -14,3 +14,35 @@ __rust_helper void rust_helper_init_work_with_key(struct work_struct *work,
>  	INIT_LIST_HEAD(&work->entry);
>  	work->func = func;
>  }
> +
> +__rust_helper bool rust_helper_work_pending(struct work_struct *work)
> +{
> +	return work_pending(work);
> +}
> +
> +__rust_helper bool rust_helper_cancel_work_sync(struct work_struct *work)
> +{
> +	return cancel_work_sync(work);
> +}
> +
> +__rust_helper bool rust_helper_cancel_delayed_work_sync(struct delayed_work *dwork)
> +{
> +	return cancel_delayed_work_sync(dwork);
> +}
> +
> +__rust_helper void rust_helper_init_delayed_work(struct delayed_work *dwork,
> +						 work_func_t func,
> +						 const char *name,
> +						 struct lock_class_key *key,
> +						 const char *tname,
> +						 struct lock_class_key *tkey)
> +{
> +	INIT_DELAYED_WORK(dwork, func);

This is just broken. You're initializing things multiple times.

> +	lockdep_init_map(&dwork->work.lockdep_map, name, key, 0);

The two lines above can just be

    rust_helper_init_work(&dwork->work, func, 0, name, key);

> +	timer_init_key(&dwork->timer, dwork->timer.function, TIMER_IRQSAFE, tname, tkey);

The existing impl of INIT_DELAYED_WORK uses `delayed_work_timer_fn`.

> +}
> +
> +__rust_helper void *rust_helper_get_dwork_timer_fn(void)
> +{
> +	return (void *)delayed_work_timer_fn;

Why?

> +}

[PATCH v4 2/3] rust: workqueue: add safe cancellation and status methods

[Aakash Bollineni via B4 Relay]

From: Aakash Bollineni <aakash.bollineni@multicorewareinc.com>

Modernize the Rust workqueue by adding methods for status checking
and cancellation of work and delayed work items.

Specifically, this patch adds:
- is_pending(): Returns true if the work item is currently enqueued.
- cancel(): Attempts to cancel the work item before it runs.
- cancel_sync(): Synchronously cancels the work item, waiting for it
  to finish if it's already running.
Reclaims ownership if the work was pending.

Signed-off-by: Aakash Bollineni <aakash.bollineni@multicorewareinc.com>
---
 rust/kernel/workqueue.rs | 333 ++++++++++++++++++++++++++++++++++++++++++-----
 1 file changed, 298 insertions(+), 35 deletions(-)

diff --git a/rust/kernel/workqueue.rs b/rust/kernel/workqueue.rs
index 706e833e9702..94a52c278776 100644
--- a/rust/kernel/workqueue.rs
+++ b/rust/kernel/workqueue.rs
@@ -448,8 +448,26 @@ pub unsafe trait WorkItemPointer<const ID: u64>: RawWorkItem<ID> {
     /// The provided `work_struct` pointer must originate from a previous call to [`__enqueue`]
     /// where the `queue_work_on` closure returned true, and the pointer must still be valid.
     ///
+    /// The implementation must ensure that the pointer is reclaimed (e.g., via `from_raw`)
+    /// before calling the `run` method of the underlying [`WorkItem`].
+    ///
     /// [`__enqueue`]: RawWorkItem::__enqueue
     unsafe extern "C" fn run(ptr: *mut bindings::work_struct);
+
+    /// Reclaims ownership of the pointer from the work item.
+    ///
+    /// This is called when a work item is successfully cancelled, allowing the caller
+    /// to recover the original pointer (e.g., `Arc` or `KBox`) that was "leaked"
+    /// during enqueuing.
+    ///
+    /// # Safety
+    ///
+    /// The provided `work_struct` pointer must originate from a previous call to [`__enqueue`]
+    /// where the `queue_work_on` closure returned true, and the work item must have been
+    /// successfully cancelled (i.e., `cancel_work` returned true).
+    ///
+    /// [`__enqueue`]: RawWorkItem::__enqueue
+    unsafe fn reclaim(ptr: *mut bindings::work_struct) -> Self;
 }
 
 /// Defines the method that should be called when this work item is executed.
@@ -516,6 +534,156 @@ pub fn new(name: &'static CStr, key: Pin<&'static LockClassKey>) -> impl PinInit
         })
     }
 
+    /// Returns whether the work item is currently pending.
+    ///
+    /// # Warning
+    ///
+    /// This method is inherently racy. A work item can be enqueued or start running
+    /// immediately after this check returns. Do not rely on this for correctness
+    /// logic (e.g., as a guard for unsafe operations); use it only for debugging or
+    /// non-critical status reporting.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// # use kernel::workqueue::{self, new_work, Work, WorkItem, HasWork};
+    /// # use kernel::impl_has_work;
+    /// # use kernel::sync::Arc;
+    /// # #[pin_data]
+    /// # struct MyStruct { #[pin] work: Work<MyStruct> }
+    /// # impl_has_work! { impl HasWork<Self> for MyStruct { self.work } }
+    /// # impl WorkItem for MyStruct {
+    /// #     type Pointer = Arc<MyStruct>;
+    /// #     fn run(_this: Arc<MyStruct>) {}
+    /// # }
+    /// let my_struct = Arc::pin_init(pin_init!(MyStruct {
+    ///     work <- new_work!("MyStruct::work"),
+    /// }), kernel::alloc::flags::GFP_KERNEL).unwrap();
+    /// assert!(!my_struct.work.is_pending());
+    /// workqueue::system().enqueue(my_struct.clone());
+    /// assert!(my_struct.work.is_pending());
+    /// # let _ = my_struct.work.cancel();
+    /// ```
+    #[inline]
+    pub fn is_pending(&self) -> bool {
+        // SAFETY: `self.work` is a valid pointer to a `work_struct`.
+        unsafe { bindings::work_pending(self.work.get()) }
+    }
+
+    /// Cancels the work item.
+    ///
+    /// If the work item was successfully cancelled (i.e., it was pending and had not yet
+    /// started running), the original pointer is reclaimed and returned.
+    ///
+    /// # Guarantees
+    ///
+    /// This method is non-blocking and may return while the work item is still running
+    /// on another CPU. If it returns `None`, the work item might be about to start,
+    /// is currently running, or has already finished.
+    ///
+    /// # Safety
+    ///
+    /// This is safe because ownership is only reclaimed if the kernel confirms (via
+    /// `cancel_work` returning true) that the work item is no longer in any queue and
+    /// will not be executed by the workqueue for this specific enqueue event.
+    ///
+    /// [`cancel_sync`]: Work::cancel_sync
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// # use kernel::workqueue::{self, new_work, Work, WorkItem, HasWork};
+    /// # use kernel::impl_has_work;
+    /// # use kernel::sync::Arc;
+    /// # #[pin_data]
+    /// # struct MyStruct { #[pin] work: Work<MyStruct> }
+    /// # impl_has_work! { impl HasWork<Self> for MyStruct { self.work } }
+    /// # impl WorkItem for MyStruct {
+    /// #     type Pointer = Arc<MyStruct>;
+    /// #     fn run(_this: Arc<MyStruct>) {}
+    /// # }
+    /// let my_struct = Arc::pin_init(pin_init!(MyStruct {
+    ///     work <- new_work!("MyStruct::work"),
+    /// }), kernel::alloc::flags::GFP_KERNEL).unwrap();
+    /// workqueue::system().enqueue(my_struct.clone());
+    /// assert!(my_struct.work.is_pending());
+    /// let reclaimed = my_struct.work.cancel();
+    /// assert!(reclaimed.is_some());
+    /// assert!(!my_struct.work.is_pending());
+    /// ```
+    pub fn cancel(&self) -> Option<T::Pointer>
+    where
+        T: WorkItem<ID>,
+    {
+        let work_ptr = self.work.get();
+        // SAFETY: `work_ptr` is a valid pointer to a `work_struct`.
+        if unsafe { bindings::cancel_work(work_ptr) } {
+            // SAFETY: The work item was successfully cancelled and is guaranteed not to run,
+            // so we can safely reclaim the ownership leaked during `enqueue`.
+            Some(unsafe { T::Pointer::reclaim(work_ptr) })
+        } else {
+            None
+        }
+    }
+
+    /// Synchronously cancels the work item.
+    ///
+    /// This method waits for the work item to finish if it is currently running.
+    /// If the work item was successfully cancelled from the queue, the pointer is
+    /// reclaimed and returned.
+    ///
+    /// # Guarantees
+    ///
+    /// After this method returns, the work item is guaranteed to be:
+    /// - Not pending in any queue.
+    /// - Not running on any CPU.
+    ///
+    /// This makes it safe to use during teardown (e.g., driver `remove` or object `drop`)
+    /// to ensure no background tasks are accessing resources that are about to be freed.
+    ///
+    /// # Safety
+    ///
+    /// Same as [`cancel`], it only reclaims ownership if the kernel confirms the work
+    /// was still pending and is now removed.
+    ///
+    /// [`cancel`]: Work::cancel
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// # use kernel::workqueue::{self, new_work, Work, WorkItem, HasWork};
+    /// # use kernel::impl_has_work;
+    /// # use kernel::sync::Arc;
+    /// # #[pin_data]
+    /// # struct MyStruct { #[pin] work: Work<MyStruct> }
+    /// # impl_has_work! { impl HasWork<Self> for MyStruct { self.work } }
+    /// # impl WorkItem for MyStruct {
+    /// #     type Pointer = Arc<MyStruct>;
+    /// #     fn run(_this: Arc<MyStruct>) {}
+    /// # }
+    /// let my_struct = Arc::pin_init(pin_init!(MyStruct {
+    ///     work <- new_work!("MyStruct::work"),
+    /// }), kernel::alloc::flags::GFP_KERNEL).unwrap();
+    /// workqueue::system().enqueue(my_struct.clone());
+    /// let reclaimed = my_struct.work.cancel_sync();
+    /// assert!(reclaimed.is_some());
+    /// ```
+    pub fn cancel_sync(&self) -> Option<T::Pointer>
+    where
+        T: WorkItem<ID>,
+    {
+        let work_ptr = self.work.get();
+        // SAFETY: `work_ptr` is a valid pointer to a `work_struct`.
+        if unsafe { bindings::cancel_work_sync(work_ptr) } {
+            // SAFETY: The work item was successfully cancelled/waited for, and is guaranteed
+            // not to run again unless re-enqueued. We reclaim the ownership leaked during
+            // `enqueue`.
+            Some(unsafe { T::Pointer::reclaim(work_ptr) })
+        } else {
+            None
+        }
+    }
+
     /// Get a pointer to the inner `work_struct`.
     ///
     /// # Safety
@@ -674,25 +842,14 @@ pub fn new(
         pin_init!(Self {
             dwork <- Opaque::ffi_init(|slot: *mut bindings::delayed_work| {
                 // SAFETY: The `WorkItemPointer` implementation promises that `run` can be used as
-                // the work item function.
+                // the work item function. We use the C-helper to ensure the timer function
+                // and data are initialized correctly according to kernel macros.
                 unsafe {
-                    bindings::init_work_with_key(
-                        core::ptr::addr_of_mut!((*slot).work),
+                    bindings::init_delayed_work(
+                        slot,
                         Some(T::Pointer::run),
-                        false,
                         work_name.as_char_ptr(),
                         work_key.as_ptr(),
-                    )
-                }
-
-                // SAFETY: The `delayed_work_timer_fn` function pointer can be used here because
-                // the timer is embedded in a `struct delayed_work`, and only ever scheduled via
-                // the core workqueue code, and configured to run in irqsafe context.
-                unsafe {
-                    bindings::timer_init_key(
-                        core::ptr::addr_of_mut!((*slot).timer),
-                        Some(bindings::delayed_work_timer_fn),
-                        bindings::TIMER_IRQSAFE,
                         timer_name.as_char_ptr(),
                         timer_key.as_ptr(),
                     )
@@ -702,6 +859,89 @@ pub fn new(
         })
     }
 
+    /// Returns whether the work item is currently pending.
+    ///
+    /// # Warning
+    ///
+    /// This method is inherently racy. See [`Work::is_pending`].
+    ///
+    /// # Examples
+    ///
+    /// See [`Work::is_pending`].
+    ///
+    /// [`Work::is_pending`]: Work::is_pending
+    #[inline]
+    pub fn is_pending(&self) -> bool {
+        // SAFETY: `self.dwork` is reaching into a valid Opaque<bindings::delayed_work>.
+        unsafe {
+            let ptr: *mut bindings::delayed_work = self.dwork.get();
+            bindings::work_pending(core::ptr::addr_of_mut!((*ptr).work))
+        }
+    }
+
+    /// Cancels the delayed work item.
+    ///
+    /// If the work item was successfully cancelled (i.e., it was pending and had not yet
+    /// started running), the original pointer is reclaimed and returned.
+    ///
+    /// # Guarantees
+    ///
+    /// See [`Work::cancel`].
+    ///
+    /// # Safety
+    ///
+    /// Same as [`Work::cancel`].
+    ///
+    /// [`cancel_sync`]: DelayedWork::cancel_sync
+    /// [`Work::cancel`]: Work::cancel
+    ///
+    /// # Examples
+    ///
+    /// See [`Work::cancel`].
+    pub fn cancel(&self) -> Option<T::Pointer>
+    where
+        T: WorkItem<ID>,
+    {
+        let dwork_ptr = self.dwork.get();
+        // SAFETY: `dwork_ptr` is a valid pointer to a `delayed_work`.
+        if unsafe { bindings::cancel_delayed_work(dwork_ptr) } {
+            // SAFETY: The work item was successfully cancelled and is guaranteed not to run,
+            // so we can safely reclaim the ownership leaked during `enqueue`.
+            Some(unsafe { T::Pointer::reclaim(core::ptr::addr_of_mut!((*dwork_ptr).work)) })
+        } else {
+            None
+        }
+    }
+
+    /// Synchronously cancels the delayed work item.
+    ///
+    /// This method waits for the work item to finish if it is currently running.
+    /// If the work item was successfully cancelled from the queue, the pointer is
+    /// reclaimed and returned.
+    ///
+    /// # Guarantees
+    ///
+    /// See [`Work::cancel_sync`].
+    ///
+    /// # Safety
+    ///
+    /// Same as [`Work::cancel_sync`].
+    pub fn cancel_sync(&self) -> Option<T::Pointer>
+    where
+        T: WorkItem<ID>,
+    {
+        let dwork_ptr = self.dwork.get();
+        // SAFETY: `dwork_ptr` is a valid pointer to a `delayed_work`.
+        if unsafe { bindings::cancel_delayed_work_sync(dwork_ptr) } {
+            // SAFETY: The work item was successfully cancelled/waited for, and is guaranteed
+            // not to run again unless re-enqueued. We reclaim the ownership leaked during
+            // `enqueue`.
+            Some(unsafe { T::Pointer::reclaim(core::ptr::addr_of_mut!((*dwork_ptr).work)) })
+        } else {
+            None
+        }
+    }
+
     /// Get a pointer to the inner `delayed_work`.
     ///
     /// # Safety
@@ -781,22 +1021,11 @@ unsafe fn raw_get_work(
             unsafe fn work_container_of(
                 ptr: *mut $crate::workqueue::Work<$work_type $(, $id)?>,
             ) -> *mut Self {
-                // SAFETY: The caller promises that the pointer points at a field of the right type
-                // in the right kind of struct.
-                let ptr = unsafe { $crate::workqueue::Work::raw_get(ptr) };
-
-                // SAFETY: The caller promises that the pointer points at a field of the right type
-                // in the right kind of struct.
-                let delayed_work = unsafe {
-                    $crate::container_of!(ptr, $crate::bindings::delayed_work, work)
-                };
-
-                let delayed_work: *mut $crate::workqueue::DelayedWork<$work_type $(, $id)?> =
-                    delayed_work.cast();
-
-                // SAFETY: The caller promises that the pointer points at a field of the right type
-                // in the right kind of struct.
-                unsafe { $crate::container_of!(delayed_work, Self, $field) }
+                // SAFETY: The caller promises that the pointer points at the `work` field
+                // of a `delayed_work` struct, which is itself the `dwork` field of a
+                // `DelayedWork` wrapper, which is the `$field` field of a `Self` struct.
+                let ptr = ptr.cast::<$crate::workqueue::DelayedWork<$work_type $(, $id)?>>();
+                unsafe { $crate::container_of!(ptr, Self, $field) }
             }
         }
     )*};
@@ -827,6 +1056,15 @@ unsafe impl<T, const ID: u64> WorkItemPointer<ID> for Arc<T>
 
         T::run(arc)
     }
+
+    unsafe fn reclaim(ptr: *mut bindings::work_struct) -> Self {
+        // The `__enqueue` method always uses a `work_struct` stored in a `Work<T, ID>`.
+        let ptr = ptr.cast::<Work<T, ID>>();
+        // SAFETY: This computes the pointer that `__enqueue` got from `Arc::into_raw`.
+        let ptr = unsafe { T::work_container_of(ptr) };
+        // SAFETY: This pointer comes from `Arc::into_raw` and we've been given back ownership.
+        unsafe { Arc::from_raw(ptr) }
+    }
 }
 
 // SAFETY: The `work_struct` raw pointer is guaranteed to be valid for the duration of the call to
@@ -874,7 +1112,8 @@ unsafe impl<T, const ID: u64> RawDelayedWorkItem<ID> for Arc<T>
 {
 }
 
-// SAFETY: TODO.
+// SAFETY: The `WorkItemPointer` implementation for `Pin<KBox<T>>` is safe because `KBox::from_raw`
+// correctly reconstructs the box that was leaked during `enqueue` (via `KBox::into_raw`).
 unsafe impl<T, const ID: u64> WorkItemPointer<ID> for Pin<KBox<T>>
 where
     T: WorkItem<ID, Pointer = Self>,
@@ -883,18 +1122,35 @@ unsafe impl<T, const ID: u64> WorkItemPointer<ID> for Pin<KBox<T>>
     unsafe extern "C" fn run(ptr: *mut bindings::work_struct) {
         // The `__enqueue` method always uses a `work_struct` stored in a `Work<T, ID>`.
         let ptr = ptr.cast::<Work<T, ID>>();
-        // SAFETY: This computes the pointer that `__enqueue` got from `Arc::into_raw`.
+        // SAFETY: This computes the pointer that `__enqueue` got from `KBox::into_raw`.
         let ptr = unsafe { T::work_container_of(ptr) };
-        // SAFETY: This pointer comes from `Arc::into_raw` and we've been given back ownership.
+        // SAFETY: This pointer comes from `KBox::into_raw` and we've been given back ownership.
         let boxed = unsafe { KBox::from_raw(ptr) };
         // SAFETY: The box was already pinned when it was enqueued.
         let pinned = unsafe { Pin::new_unchecked(boxed) };
 
         T::run(pinned)
     }
+
+    unsafe fn reclaim(ptr: *mut bindings::work_struct) -> Self {
+        // The `__enqueue` method always uses a `work_struct` stored in a `Work<T, ID>`.
+        let ptr = ptr.cast::<Work<T, ID>>();
+        // SAFETY: This computes the pointer that `__enqueue` got from `KBox::into_raw`.
+        let ptr = unsafe { T::work_container_of(ptr) };
+        // SAFETY: This pointer comes from `KBox::into_raw` and we've been given back ownership.
+        let boxed = unsafe { KBox::from_raw(ptr) };
+        // SAFETY: The box was already pinned when it was enqueued.
+        unsafe { Pin::new_unchecked(boxed) }
+    }
 }
 
-// SAFETY: TODO.
+// SAFETY: The `work_struct` raw pointer is guaranteed to be valid for the duration of the call to
+// the closure because we have exclusive ownership of the `KBox`, and we don't drop it ourselves.
+// If `queue_work_on` returns true, it is further guaranteed to be valid until a call to the
+// function pointer in `work_struct` because we leak the memory it points to, and only reclaim it
+// if the closure returns false (not reachable for KBox as it must succeed) or in
+// `WorkItemPointer::run`, which is what the function pointer in the `work_struct` must be
+// pointing to.
 unsafe impl<T, const ID: u64> RawWorkItem<ID> for Pin<KBox<T>>
 where
     T: WorkItem<ID, Pointer = Self>,
@@ -1022,3 +1278,10 @@ pub fn system_bh_highpri() -> &'static Queue {
     // SAFETY: `system_bh_highpri_wq` is a C global, always available.
     unsafe { Queue::from_raw(bindings::system_bh_highpri_wq) }
 }
+
+/// Returns the strong count of an [`Arc`] for testing purposes.
+///
+/// # Safety
+///
+/// This is intended for use in KUnit tests and sample modules ONLY.
+#[cfg(CONFIG_KUNIT)]

-- 
2.43.0

Re: [PATCH v4 2/3] rust: workqueue: add safe cancellation and status methods

[Onur Özkan]

> From: Aakash Bollineni <aakash.bollineni@multicorewareinc.com>
> 
> Modernize the Rust workqueue by adding methods for status checking
> and cancellation of work and delayed work items.
> 
> Specifically, this patch adds:
> - is_pending(): Returns true if the work item is currently enqueued.
> - cancel(): Attempts to cancel the work item before it runs.
> - cancel_sync(): Synchronously cancels the work item, waiting for it
>   to finish if it's already running.
> Reclaims ownership if the work was pending.
> 
> Signed-off-by: Aakash Bollineni <aakash.bollineni@multicorewareinc.com>
> ---
>  rust/kernel/workqueue.rs | 333 ++++++++++++++++++++++++++++++++++++++++++-----
>  1 file changed, 298 insertions(+), 35 deletions(-)
> 
> diff --git a/rust/kernel/workqueue.rs b/rust/kernel/workqueue.rs
> index 706e833e9702..94a52c278776 100644
> --- a/rust/kernel/workqueue.rs
> +++ b/rust/kernel/workqueue.rs
> @@ -448,8 +448,26 @@ pub unsafe trait WorkItemPointer<const ID: u64>: RawWorkItem<ID> {
>      /// The provided `work_struct` pointer must originate from a previous call to [`__enqueue`]
>      /// where the `queue_work_on` closure returned true, and the pointer must still be valid.
>      ///
> +    /// The implementation must ensure that the pointer is reclaimed (e.g., via `from_raw`)
> +    /// before calling the `run` method of the underlying [`WorkItem`].
> +    ///
>      /// [`__enqueue`]: RawWorkItem::__enqueue
>      unsafe extern "C" fn run(ptr: *mut bindings::work_struct);
> +
> +    /// Reclaims ownership of the pointer from the work item.
> +    ///
> +    /// This is called when a work item is successfully cancelled, allowing the caller
> +    /// to recover the original pointer (e.g., `Arc` or `KBox`) that was "leaked"
> +    /// during enqueuing.
> +    ///
> +    /// # Safety
> +    ///
> +    /// The provided `work_struct` pointer must originate from a previous call to [`__enqueue`]
> +    /// where the `queue_work_on` closure returned true, and the work item must have been
> +    /// successfully cancelled (i.e., `cancel_work` returned true).
> +    ///
> +    /// [`__enqueue`]: RawWorkItem::__enqueue
> +    unsafe fn reclaim(ptr: *mut bindings::work_struct) -> Self;
>  }
>  
>  /// Defines the method that should be called when this work item is executed.
> @@ -516,6 +534,156 @@ pub fn new(name: &'static CStr, key: Pin<&'static LockClassKey>) -> impl PinInit
>          })
>      }
>  
> +    /// Returns whether the work item is currently pending.
> +    ///
> +    /// # Warning
> +    ///
> +    /// This method is inherently racy. A work item can be enqueued or start running
> +    /// immediately after this check returns. Do not rely on this for correctness
> +    /// logic (e.g., as a guard for unsafe operations); use it only for debugging or
> +    /// non-critical status reporting.
> +    ///
> +    /// # Examples
> +    ///
> +    /// ```
> +    /// # use kernel::workqueue::{self, new_work, Work, WorkItem, HasWork};
> +    /// # use kernel::impl_has_work;
> +    /// # use kernel::sync::Arc;
> +    /// # #[pin_data]
> +    /// # struct MyStruct { #[pin] work: Work<MyStruct> }
> +    /// # impl_has_work! { impl HasWork<Self> for MyStruct { self.work } }
> +    /// # impl WorkItem for MyStruct {
> +    /// #     type Pointer = Arc<MyStruct>;
> +    /// #     fn run(_this: Arc<MyStruct>) {}
> +    /// # }
> +    /// let my_struct = Arc::pin_init(pin_init!(MyStruct {
> +    ///     work <- new_work!("MyStruct::work"),
> +    /// }), kernel::alloc::flags::GFP_KERNEL).unwrap();
> +    /// assert!(!my_struct.work.is_pending());
> +    /// workqueue::system().enqueue(my_struct.clone());
> +    /// assert!(my_struct.work.is_pending());
> +    /// # let _ = my_struct.work.cancel();
> +    /// ```

Can you add some spaces between certain lines? The bulk style makes it quite
hard to follow in my opinion. This applies to other examples too.

> +    #[inline]
> +    pub fn is_pending(&self) -> bool {
> +        // SAFETY: `self.work` is a valid pointer to a `work_struct`.
> +        unsafe { bindings::work_pending(self.work.get()) }
> +    }
> +
> +    /// Cancels the work item.
> +    ///
> +    /// If the work item was successfully cancelled (i.e., it was pending and had not yet
> +    /// started running), the original pointer is reclaimed and returned.
> +    ///
> +    /// # Guarantees
> +    ///
> +    /// This method is non-blocking and may return while the work item is still running
> +    /// on another CPU. If it returns `None`, the work item might be about to start,
> +    /// is currently running, or has already finished.
> +    ///
> +    /// # Safety
> +    ///
> +    /// This is safe because ownership is only reclaimed if the kernel confirms (via
> +    /// `cancel_work` returning true) that the work item is no longer in any queue and
> +    /// will not be executed by the workqueue for this specific enqueue event.
> +    ///
> +    /// [`cancel_sync`]: Work::cancel_sync

Why not using [`Work::cancel_sync`] directly?

> +    ///
> +    /// # Examples
> +    ///
> +    /// ```
> +    /// # use kernel::workqueue::{self, new_work, Work, WorkItem, HasWork};
> +    /// # use kernel::impl_has_work;
> +    /// # use kernel::sync::Arc;
> +    /// # #[pin_data]
> +    /// # struct MyStruct { #[pin] work: Work<MyStruct> }
> +    /// # impl_has_work! { impl HasWork<Self> for MyStruct { self.work } }
> +    /// # impl WorkItem for MyStruct {
> +    /// #     type Pointer = Arc<MyStruct>;
> +    /// #     fn run(_this: Arc<MyStruct>) {}
> +    /// # }
> +    /// let my_struct = Arc::pin_init(pin_init!(MyStruct {
> +    ///     work <- new_work!("MyStruct::work"),
> +    /// }), kernel::alloc::flags::GFP_KERNEL).unwrap();
> +    /// workqueue::system().enqueue(my_struct.clone());
> +    /// assert!(my_struct.work.is_pending());
> +    /// let reclaimed = my_struct.work.cancel();
> +    /// assert!(reclaimed.is_some());
> +    /// assert!(!my_struct.work.is_pending());
> +    /// ```
> +    pub fn cancel(&self) -> Option<T::Pointer>
> +    where
> +        T: WorkItem<ID>,
> +    {
> +        let work_ptr = self.work.get();
> +        // SAFETY: `work_ptr` is a valid pointer to a `work_struct`.
> +        if unsafe { bindings::cancel_work(work_ptr) } {
> +            // SAFETY: The work item was successfully cancelled and is guaranteed not to run,
> +            // so we can safely reclaim the ownership leaked during `enqueue`.
> +            Some(unsafe { T::Pointer::reclaim(work_ptr) })
> +        } else {
> +            None
> +        }
> +    }
> +
> +    /// Synchronously cancels the work item.
> +    ///
> +    /// This method waits for the work item to finish if it is currently running.
> +    /// If the work item was successfully cancelled from the queue, the pointer is
> +    /// reclaimed and returned.
> +    ///
> +    /// # Guarantees
> +    ///
> +    /// After this method returns, the work item is guaranteed to be:
> +    /// - Not pending in any queue.
> +    /// - Not running on any CPU.
> +    ///
> +    /// This makes it safe to use during teardown (e.g., driver `remove` or object `drop`)
> +    /// to ensure no background tasks are accessing resources that are about to be freed.
> +    ///
> +    /// # Safety
> +    ///
> +    /// Same as [`cancel`], it only reclaims ownership if the kernel confirms the work
> +    /// was still pending and is now removed.
> +    ///
> +    /// [`cancel`]: Work::cancel
> +    ///
> +    /// # Examples
> +    ///
> +    /// ```
> +    /// # use kernel::workqueue::{self, new_work, Work, WorkItem, HasWork};
> +    /// # use kernel::impl_has_work;
> +    /// # use kernel::sync::Arc;
> +    /// # #[pin_data]
> +    /// # struct MyStruct { #[pin] work: Work<MyStruct> }
> +    /// # impl_has_work! { impl HasWork<Self> for MyStruct { self.work } }
> +    /// # impl WorkItem for MyStruct {
> +    /// #     type Pointer = Arc<MyStruct>;
> +    /// #     fn run(_this: Arc<MyStruct>) {}
> +    /// # }
> +    /// let my_struct = Arc::pin_init(pin_init!(MyStruct {
> +    ///     work <- new_work!("MyStruct::work"),
> +    /// }), kernel::alloc::flags::GFP_KERNEL).unwrap();
> +    /// workqueue::system().enqueue(my_struct.clone());
> +    /// let reclaimed = my_struct.work.cancel_sync();
> +    /// assert!(reclaimed.is_some());
> +    /// ```
> +    pub fn cancel_sync(&self) -> Option<T::Pointer>
> +    where
> +        T: WorkItem<ID>,
> +    {
> +        let work_ptr = self.work.get();
> +        // SAFETY: `work_ptr` is a valid pointer to a `work_struct`.
> +        if unsafe { bindings::cancel_work_sync(work_ptr) } {
> +            // SAFETY: The work item was successfully cancelled/waited for, and is guaranteed
> +            // not to run again unless re-enqueued. We reclaim the ownership leaked during
> +            // `enqueue`.
> +            Some(unsafe { T::Pointer::reclaim(work_ptr) })
> +        } else {
> +            None
> +        }
> +    }
> +
>      /// Get a pointer to the inner `work_struct`.
>      ///
>      /// # Safety
> @@ -674,25 +842,14 @@ pub fn new(
>          pin_init!(Self {
>              dwork <- Opaque::ffi_init(|slot: *mut bindings::delayed_work| {
>                  // SAFETY: The `WorkItemPointer` implementation promises that `run` can be used as
> -                // the work item function.
> +                // the work item function. We use the C-helper to ensure the timer function
> +                // and data are initialized correctly according to kernel macros.
>                  unsafe {
> -                    bindings::init_work_with_key(
> -                        core::ptr::addr_of_mut!((*slot).work),
> +                    bindings::init_delayed_work(
> +                        slot,
>                          Some(T::Pointer::run),
> -                        false,
>                          work_name.as_char_ptr(),
>                          work_key.as_ptr(),
> -                    )
> -                }
> -
> -                // SAFETY: The `delayed_work_timer_fn` function pointer can be used here because
> -                // the timer is embedded in a `struct delayed_work`, and only ever scheduled via
> -                // the core workqueue code, and configured to run in irqsafe context.
> -                unsafe {
> -                    bindings::timer_init_key(
> -                        core::ptr::addr_of_mut!((*slot).timer),
> -                        Some(bindings::delayed_work_timer_fn),
> -                        bindings::TIMER_IRQSAFE,
>                          timer_name.as_char_ptr(),
>                          timer_key.as_ptr(),
>                      )
> @@ -702,6 +859,89 @@ pub fn new(
>          })
>      }
>  
> +    /// Returns whether the work item is currently pending.
> +    ///
> +    /// # Warning
> +    ///
> +    /// This method is inherently racy. See [`Work::is_pending`].
> +    ///
> +    /// # Examples
> +    ///
> +    /// See [`Work::is_pending`].
> +    ///
> +    /// [`Work::is_pending`]: Work::is_pending

I guess this is a leftover or something? It doesn't seem to make any sense.

> +    #[inline]
> +    pub fn is_pending(&self) -> bool {
> +        // SAFETY: `self.dwork` is reaching into a valid Opaque<bindings::delayed_work>.
> +        unsafe {
> +            let ptr: *mut bindings::delayed_work = self.dwork.get();
> +            bindings::work_pending(core::ptr::addr_of_mut!((*ptr).work))
> +        }
> +    }
> +
> +    /// Cancels the delayed work item.
> +    ///
> +    /// If the work item was successfully cancelled (i.e., it was pending and had not yet
> +    /// started running), the original pointer is reclaimed and returned.
> +    ///
> +    /// # Guarantees
> +    ///
> +    /// See [`Work::cancel`].
> +    ///
> +    /// # Safety
> +    ///
> +    /// Same as [`Work::cancel`].
> +    ///
> +    /// [`cancel_sync`]: DelayedWork::cancel_sync
> +    /// [`Work::cancel`]: Work::cancel

1- Same as above, these don't make any sense.
2- cancel_sync is not used anywhere. I assume the refs are wrong?

> +    ///
> +    /// # Examples
> +    ///
> +    /// See [`Work::cancel`].
> +    pub fn cancel(&self) -> Option<T::Pointer>
> +    where
> +        T: WorkItem<ID>,
> +    {
> +        let dwork_ptr = self.dwork.get();
> +        // SAFETY: `dwork_ptr` is a valid pointer to a `delayed_work`.
> +        if unsafe { bindings::cancel_delayed_work(dwork_ptr) } {
> +            // SAFETY: The work item was successfully cancelled and is guaranteed not to run,
> +            // so we can safely reclaim the ownership leaked during `enqueue`.
> +            Some(unsafe { T::Pointer::reclaim(core::ptr::addr_of_mut!((*dwork_ptr).work)) })
> +        } else {
> +            None
> +        }
> +    }
> +
> +    /// Synchronously cancels the delayed work item.
> +    ///
> +    /// This method waits for the work item to finish if it is currently running.
> +    /// If the work item was successfully cancelled from the queue, the pointer is
> +    /// reclaimed and returned.
> +    ///
> +    /// # Guarantees
> +    ///
> +    /// See [`Work::cancel_sync`].
> +    ///
> +    /// # Safety
> +    ///
> +    /// Same as [`Work::cancel_sync`].
> +    pub fn cancel_sync(&self) -> Option<T::Pointer>
> +    where
> +        T: WorkItem<ID>,
> +    {
> +        let dwork_ptr = self.dwork.get();
> +        // SAFETY: `dwork_ptr` is a valid pointer to a `delayed_work`.
> +        if unsafe { bindings::cancel_delayed_work_sync(dwork_ptr) } {
> +            // SAFETY: The work item was successfully cancelled/waited for, and is guaranteed
> +            // not to run again unless re-enqueued. We reclaim the ownership leaked during
> +            // `enqueue`.
> +            Some(unsafe { T::Pointer::reclaim(core::ptr::addr_of_mut!((*dwork_ptr).work)) })
> +        } else {
> +            None
> +        }
> +    }
> +
>      /// Get a pointer to the inner `delayed_work`.
>      ///
>      /// # Safety
> @@ -781,22 +1021,11 @@ unsafe fn raw_get_work(
>              unsafe fn work_container_of(
>                  ptr: *mut $crate::workqueue::Work<$work_type $(, $id)?>,
>              ) -> *mut Self {
> -                // SAFETY: The caller promises that the pointer points at a field of the right type
> -                // in the right kind of struct.
> -                let ptr = unsafe { $crate::workqueue::Work::raw_get(ptr) };
> -
> -                // SAFETY: The caller promises that the pointer points at a field of the right type
> -                // in the right kind of struct.
> -                let delayed_work = unsafe {
> -                    $crate::container_of!(ptr, $crate::bindings::delayed_work, work)
> -                };
> -
> -                let delayed_work: *mut $crate::workqueue::DelayedWork<$work_type $(, $id)?> =
> -                    delayed_work.cast();
> -
> -                // SAFETY: The caller promises that the pointer points at a field of the right type
> -                // in the right kind of struct.
> -                unsafe { $crate::container_of!(delayed_work, Self, $field) }
> +                // SAFETY: The caller promises that the pointer points at the `work` field
> +                // of a `delayed_work` struct, which is itself the `dwork` field of a
> +                // `DelayedWork` wrapper, which is the `$field` field of a `Self` struct.
> +                let ptr = ptr.cast::<$crate::workqueue::DelayedWork<$work_type $(, $id)?>>();
> +                unsafe { $crate::container_of!(ptr, Self, $field) }
>              }
>          }
>      )*};
> @@ -827,6 +1056,15 @@ unsafe impl<T, const ID: u64> WorkItemPointer<ID> for Arc<T>
>  
>          T::run(arc)
>      }
> +
> +    unsafe fn reclaim(ptr: *mut bindings::work_struct) -> Self {

Missing # SAFETY contract.

> +        // The `__enqueue` method always uses a `work_struct` stored in a `Work<T, ID>`.
> +        let ptr = ptr.cast::<Work<T, ID>>();
> +        // SAFETY: This computes the pointer that `__enqueue` got from `Arc::into_raw`.
> +        let ptr = unsafe { T::work_container_of(ptr) };
> +        // SAFETY: This pointer comes from `Arc::into_raw` and we've been given back ownership.
> +        unsafe { Arc::from_raw(ptr) }
> +    }
>  }
>  
>  // SAFETY: The `work_struct` raw pointer is guaranteed to be valid for the duration of the call to
> @@ -874,7 +1112,8 @@ unsafe impl<T, const ID: u64> RawDelayedWorkItem<ID> for Arc<T>
>  {
>  }
>  
> -// SAFETY: TODO.
> +// SAFETY: The `WorkItemPointer` implementation for `Pin<KBox<T>>` is safe because `KBox::from_raw`
> +// correctly reconstructs the box that was leaked during `enqueue` (via `KBox::into_raw`).
>  unsafe impl<T, const ID: u64> WorkItemPointer<ID> for Pin<KBox<T>>
>  where
>      T: WorkItem<ID, Pointer = Self>,
> @@ -883,18 +1122,35 @@ unsafe impl<T, const ID: u64> WorkItemPointer<ID> for Pin<KBox<T>>
>      unsafe extern "C" fn run(ptr: *mut bindings::work_struct) {
>          // The `__enqueue` method always uses a `work_struct` stored in a `Work<T, ID>`.
>          let ptr = ptr.cast::<Work<T, ID>>();
> -        // SAFETY: This computes the pointer that `__enqueue` got from `Arc::into_raw`.
> +        // SAFETY: This computes the pointer that `__enqueue` got from `KBox::into_raw`.
>          let ptr = unsafe { T::work_container_of(ptr) };
> -        // SAFETY: This pointer comes from `Arc::into_raw` and we've been given back ownership.
> +        // SAFETY: This pointer comes from `KBox::into_raw` and we've been given back ownership.
>          let boxed = unsafe { KBox::from_raw(ptr) };
>          // SAFETY: The box was already pinned when it was enqueued.
>          let pinned = unsafe { Pin::new_unchecked(boxed) };
>  
>          T::run(pinned)
>      }
> +
> +    unsafe fn reclaim(ptr: *mut bindings::work_struct) -> Self {

Same here, missing # SAFETY contract.

> +        // The `__enqueue` method always uses a `work_struct` stored in a `Work<T, ID>`.
> +        let ptr = ptr.cast::<Work<T, ID>>();
> +        // SAFETY: This computes the pointer that `__enqueue` got from `KBox::into_raw`.
> +        let ptr = unsafe { T::work_container_of(ptr) };
> +        // SAFETY: This pointer comes from `KBox::into_raw` and we've been given back ownership.
> +        let boxed = unsafe { KBox::from_raw(ptr) };
> +        // SAFETY: The box was already pinned when it was enqueued.
> +        unsafe { Pin::new_unchecked(boxed) }
> +    }
>  }
>  
> -// SAFETY: TODO.
> +// SAFETY: The `work_struct` raw pointer is guaranteed to be valid for the duration of the call to
> +// the closure because we have exclusive ownership of the `KBox`, and we don't drop it ourselves.
> +// If `queue_work_on` returns true, it is further guaranteed to be valid until a call to the
> +// function pointer in `work_struct` because we leak the memory it points to, and only reclaim it
> +// if the closure returns false (not reachable for KBox as it must succeed) or in
> +// `WorkItemPointer::run`, which is what the function pointer in the `work_struct` must be
> +// pointing to.
>  unsafe impl<T, const ID: u64> RawWorkItem<ID> for Pin<KBox<T>>
>  where
>      T: WorkItem<ID, Pointer = Self>,
> @@ -1022,3 +1278,10 @@ pub fn system_bh_highpri() -> &'static Queue {
>      // SAFETY: `system_bh_highpri_wq` is a C global, always available.
>      unsafe { Queue::from_raw(bindings::system_bh_highpri_wq) }
>  }
> +
> +/// Returns the strong count of an [`Arc`] for testing purposes.
> +///
> +/// # Safety
> +///
> +/// This is intended for use in KUnit tests and sample modules ONLY.
> +#[cfg(CONFIG_KUNIT)]
> 

Seems like this part failed on the patch separation.

> -- 
> 2.43.0
> 
> 

[PATCH v4 3/3] rust: workqueue: add KUnit and sample stress tests

[Aakash Bollineni via B4 Relay]

From: Aakash Bollineni <aakash.bollineni@multicorewareinc.com>

To ensure the safety and correctness of the improved workqueue API,
this patch adds comprehensive testing infrastructure:
1. KUnit Tests: Adds an internal 'rust_kernel_workqueue' test suite
   to rust/kernel/workqueue.rs.
2. Sample Module: Updates samples/rust/rust_workqueue_test.rs for
   stress verification.

Reported-by: kernel test robot <lkp@intel.com>
Closes: https://lore.kernel.org/oe-kbuild-all/202604071427.209bk.JHO@intel.com/
v4: Fixed rustfmt and build errors in samples/rust/rust_workqueue_test.rs.
Signed-off-by: Aakash Bollineni <aakash.bollineni@multicorewareinc.com>
---
 rust/kernel/workqueue.rs            | 130 ++++++++++++++++++++++++
 samples/rust/Kconfig                |  10 ++
 samples/rust/Makefile               |   2 +
 samples/rust/rust_workqueue_test.rs | 192 ++++++++++++++++++++++++++++++++++++
 4 files changed, 334 insertions(+)

diff --git a/rust/kernel/workqueue.rs b/rust/kernel/workqueue.rs
index 94a52c278776..d25e0fa9d44c 100644
--- a/rust/kernel/workqueue.rs
+++ b/rust/kernel/workqueue.rs
@@ -1285,3 +1285,133 @@ pub fn system_bh_highpri() -> &'static Queue {
 ///
 /// This is intended for use in KUnit tests and sample modules ONLY.
 #[cfg(CONFIG_KUNIT)]
+
+#[macros::kunit_tests(rust_kernel_workqueue)]
+mod tests {
+    use super::*;
+    use crate::sync::Arc;
+
+    #[pin_data]
+    struct TestWorkItem {
+        #[pin]
+        work: Work<TestWorkItem>,
+        value: i32,
+    }
+
+    impl_has_work! {
+        impl HasWork<Self> for TestWorkItem { self.work }
+    }
+
+    impl WorkItem for TestWorkItem {
+        type Pointer = Arc<Self>;
+        fn run(_this: Arc<Self>) {}
+    }
+
+    #[pin_data]
+    struct TestDelayedWorkItem {
+        #[pin]
+        delayed_work: DelayedWork<TestDelayedWorkItem>,
+        value: i32,
+    }
+
+    impl_has_delayed_work! {
+        impl HasDelayedWork<Self> for TestDelayedWorkItem { self.delayed_work }
+    }
+
+    impl WorkItem for TestDelayedWorkItem {
+        type Pointer = Arc<Self>;
+        fn run(_this: Arc<Self>) {}
+    }
+
+    #[test]
+    fn test_work_cancel_reclaim() {
+        let item = Arc::pin_init(
+            pin_init!(TestWorkItem {
+                work <- new_work!("TestWorkItem::work"),
+                value: 42,
+            }),
+            GFP_KERNEL,
+        )
+        .expect("Failed to allocate TestWorkItem");
+
+        let initial_count = arc_count(&item);
+
+        // Enqueue
+        let _ = system().enqueue(item.clone());
+
+        // Cancel and Reclaim (if it was pending)
+        if let Some(reclaimed) = item.work.cancel() {
+            assert!(arc_count(&item) == initial_count + 1);
+            drop(reclaimed);
+            assert!(arc_count(&item) == initial_count);
+        }
+    }
+
+    #[test]
+    fn test_work_cancel_sync_reclaim() {
+        let item = Arc::pin_init(
+            pin_init!(TestWorkItem {
+                work <- new_work!("TestWorkItem::work"),
+                value: 42,
+            }),
+            GFP_KERNEL,
+        )
+        .expect("Failed to allocate TestWorkItem");
+
+        let initial_count = arc_count(&item);
+
+        // Enqueue
+        let _ = system().enqueue(item.clone());
+
+        // Cancel Sync and Reclaim
+        if let Some(reclaimed) = item.work.cancel_sync() {
+            assert!(arc_count(&item) == initial_count + 1);
+            drop(reclaimed);
+            assert!(arc_count(&item) == initial_count);
+        }
+    }
+
+    #[test]
+    fn test_work_stress_enqueue_cancel() {
+        let item = Arc::pin_init(
+            pin_init!(TestWorkItem {
+                work <- new_work!("TestWorkItem::work"),
+                value: 42,
+            }),
+            GFP_KERNEL,
+        )
+        .expect("Failed to allocate TestWorkItem");
+
+        for _ in 0..100 {
+            if let Ok(_) = system().enqueue(item.clone()) {
+                let _ = item.work.cancel_sync();
+            }
+        }
+
+        assert_eq!(arc_count(&item), 1);
+    }
+
+    #[test]
+    fn test_delayed_work_cancel_reclaim() {
+        let item = Arc::pin_init(
+            pin_init!(TestDelayedWorkItem {
+                delayed_work <- new_delayed_work!("TestDelayedWorkItem::delayed_work"),
+                value: 42,
+            }),
+            GFP_KERNEL,
+        )
+        .expect("Failed to allocate TestDelayedWorkItem");
+
+        let initial_count = arc_count(&item);
+
+        // Enqueue delayed (use a longer delay to ensure it stays pending)
+        let _ = system().enqueue_delayed(item.clone(), 1000);
+
+        // Cancel and Reclaim
+        if let Some(reclaimed) = item.delayed_work.cancel() {
+            assert!(arc_count(&item) == initial_count + 1);
+            drop(reclaimed);
+            assert!(arc_count(&item) == initial_count);
+        }
+    }
+}
diff --git a/samples/rust/Kconfig b/samples/rust/Kconfig
index c49ab9106345..b3f078f77ca2 100644
--- a/samples/rust/Kconfig
+++ b/samples/rust/Kconfig
@@ -172,6 +172,16 @@ config SAMPLE_RUST_SOC
 
 	  If unsure, say N.
 
+config SAMPLE_RUST_WORKQUEUE
+	tristate "Workqueue"
+	help
+	  This option builds the Rust workqueue robust stress test sample.
+
+	  To compile this as a module, choose M here:
+	  the module will be called rust_workqueue_test.
+
+	  If unsure, say N.
+
 config SAMPLE_RUST_HOSTPROGS
 	bool "Host programs"
 	help
diff --git a/samples/rust/Makefile b/samples/rust/Makefile
index 6c0aaa58cccc..261aa67b6502 100644
--- a/samples/rust/Makefile
+++ b/samples/rust/Makefile
@@ -20,3 +20,5 @@ obj-$(CONFIG_SAMPLE_RUST_SOC)			+= rust_soc.o
 rust_print-y := rust_print_main.o rust_print_events.o
 
 subdir-$(CONFIG_SAMPLE_RUST_HOSTPROGS)		+= hostprogs
+
+obj-$(CONFIG_SAMPLE_RUST_WORKQUEUE)		+= rust_workqueue_test.o
diff --git a/samples/rust/rust_workqueue_test.rs b/samples/rust/rust_workqueue_test.rs
new file mode 100644
index 000000000000..e21296fdb34d
--- /dev/null
+++ b/samples/rust/rust_workqueue_test.rs
@@ -0,0 +1,192 @@
+// SPDX-License-Identifier: GPL-2.0
+
+//! Robust stress test for Rust workqueue API.
+
+use kernel::prelude::*;
+use kernel::sync::Arc;
+use kernel::time::msecs_to_jiffies;
+use kernel::workqueue::{self, new_work, Work, WorkItem};
+
+#[pin_data]
+struct TestWorkItem {
+    #[pin]
+    work: Work<TestWorkItem>,
+    value: i32,
+}
+
+kernel::impl_has_work! {
+    impl HasWork<Self> for TestWorkItem { self.work }
+}
+
+impl WorkItem for TestWorkItem {
+    type Pointer = Arc<TestWorkItem>;
+
+    fn run(this: Arc<TestWorkItem>) {
+        pr_info!(
+            "Rust workqueue test: Work item running (value: {})\n",
+            this.value
+        );
+    }
+}
+
+#[pin_data]
+struct TestDelayedWorkItem {
+    #[pin]
+    delayed_work: workqueue::DelayedWork<TestDelayedWorkItem>,
+    value: i32,
+}
+
+// SAFETY: The `delayed_work` field is at a fixed offset and is valid for the lifetime of
+// `TestDelayedWorkItem`.
+unsafe impl workqueue::HasDelayedWork<Self> for TestDelayedWorkItem {}
+
+impl WorkItem for TestDelayedWorkItem {
+    type Pointer = Arc<TestDelayedWorkItem>;
+
+    fn run(this: Arc<TestDelayedWorkItem>) {
+        pr_info!(
+            "Rust workqueue test: Delayed work item running (value: {})\n",
+            this.value
+        );
+    }
+}
+
+struct RustWorkqueueTest;
+
+impl kernel::Module for RustWorkqueueTest {
+    fn init(_module: &'static ThisModule) -> Result<Self> {
+        pr_info!("Rust workqueue test: starting robust verification (v4)\n");
+
+        // 1. Basic Lifecycle with Refcount Validation (Standard Work)
+        {
+            let work_item = Arc::pin_init(
+                pin_init!(TestWorkItem {
+                    work <- new_work!("TestWorkItem::work"),
+                    value: 42,
+                }),
+                GFP_KERNEL,
+            )?;
+
+            let initial_count = workqueue::arc_count(&work_item);
+            pr_info!("Initial Arc strong count: {}\n", initial_count);
+
+            // Enqueue
+            let enqueued_item = work_item.clone();
+
+            if let Err(returned_item) = workqueue::system().enqueue(enqueued_item) {
+                pr_warn!("Work already pending, unexpected!\n");
+                let _ = returned_item;
+            } else {
+                pr_info!(
+                    "Work enqueued successfully. Strong count: {}\n",
+                    workqueue::arc_count(&work_item)
+                );
+            }
+
+            // Cancel immediately
+            if let Some(reclaimed) = work_item.work.cancel() {
+                let count_after_cancel = workqueue::arc_count(&work_item);
+                pr_info!(
+                    "Success: Work cancelled and Arc reclaimed. Strong count: {}\n",
+                    count_after_cancel
+                );
+
+                if count_after_cancel != initial_count + 1 {
+                    pr_err!(
+                        "ERROR: Refcount mismatch after cancel! Expected {}, got {}\n",
+                        initial_count + 1,
+                        count_after_cancel
+                    );
+                    return Err(ENXIO);
+                }
+                drop(reclaimed);
+                if workqueue::arc_count(&work_item) != initial_count {
+                    pr_err!("ERROR: Refcount mismatch after drop!\n");
+                    return Err(ENXIO);
+                }
+            } else {
+                pr_info!("Work already running or finished.\n");
+            }
+        }
+
+        // 2. Stress Testing: Enqueue/Cancel Sync Loop
+        {
+            pr_info!("Starting stress test (1000 iterations)...\n");
+            let work_item = Arc::pin_init(
+                pin_init!(TestWorkItem {
+                    work <- new_work!("TestWorkItem::work"),
+                    value: 99,
+                }),
+                GFP_KERNEL,
+            )?;
+
+            for i in 0..1000 {
+                let _ = workqueue::system().enqueue(work_item.clone());
+                let _ = work_item.work.cancel_sync();
+                if i % 250 == 0 {
+                    pr_info!("Stress test progress: {}/1000\n", i);
+                }
+            }
+
+            if workqueue::arc_count(&work_item) != 1 {
+                pr_err!("ERROR: Refcount leak detected after stress test!\n");
+                return Err(ENXIO);
+            } else {
+                pr_info!("Stress test completed successfully.\n");
+            }
+        }
+
+        // 3. Delayed Work Cancellation Test
+        {
+            let delayed_item = Arc::pin_init(
+                pin_init!(TestDelayedWorkItem {
+                    delayed_work <-
+                    workqueue::new_delayed_work!("TestDelayedWorkItem::delayed_work"),
+                    value: 7,
+                }),
+                GFP_KERNEL,
+            )?;
+
+            let initial_count = workqueue::arc_count(&delayed_item);
+
+            // Schedule with a long delay (5 seconds)
+            if let Err(returned) =
+                workqueue::system().enqueue_delayed(delayed_item.clone(), msecs_to_jiffies(5000))
+            {
+                drop(returned);
+            } else {
+                pr_info!(
+                    "Delayed work enqueued. count: {}\n",
+                    workqueue::arc_count(&delayed_item)
+                );
+            }
+
+            if let Some(reclaimed) = delayed_item.delayed_work.cancel() {
+                pr_info!("Success: Delayed work reclaimed. No leak.\n");
+                drop(reclaimed);
+            }
+
+            if workqueue::arc_count(&delayed_item) != initial_count {
+                pr_err!("ERROR: Refcount leak after delayed cancel!\n");
+                return Err(ENXIO);
+            }
+        }
+
+        pr_info!("Rust workqueue test: all robust checks passed\n");
+        Ok(RustWorkqueueTest)
+    }
+}
+
+impl Drop for RustWorkqueueTest {
+    fn drop(&mut self) {
+        pr_info!("Rust workqueue test: exit\n");
+    }
+}
+
+module! {
+    type: RustWorkqueueTest,
+    name: "rust_workqueue_test",
+    authors: ["Aakash Bollineni"],
+    description: "Robust stress test for Rust workqueue API",
+    license: "GPL",
+}

-- 
2.43.0