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@xxxxxxxxxxxxxxxxxxxx>
>
> 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@xxxxxxxxxxxxxxxxxxxx>
> ---
>  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?

> +}