linux-kernel - Re: [PATCH v2 1/2] rust: workqueue: restrict delayed work to global wqs

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Message-ID: <0bf00b4c-3227-4214-b8ba-929cf044d9fa@nvidia.com>
Date: Thu, 13 Nov 2025 12:40:10 -0800
From: John Hubbard <jhubbard@...dia.com>
To: Alice Ryhl <aliceryhl@...gle.com>, Tejun Heo <tj@...nel.org>,
 Miguel Ojeda <ojeda@...nel.org>
Cc: Lai Jiangshan <jiangshanlai@...il.com>, Boqun Feng
 <boqun.feng@...il.com>, Gary Guo <gary@...yguo.net>,
 Björn Roy Baron <bjorn3_gh@...tonmail.com>,
 Andreas Hindborg <a.hindborg@...nel.org>, Trevor Gross <tmgross@...ch.edu>,
 Danilo Krummrich <dakr@...nel.org>,
 Daniel Almeida <daniel.almeida@...labora.com>,
 Philipp Stanner <phasta@...nel.org>, Tamir Duberstein <tamird@...il.com>,
 rust-for-linux@...r.kernel.org, linux-kernel@...r.kernel.org,
 Benno Lossin <lossin@...nel.org>
Subject: Re: [PATCH v2 1/2] rust: workqueue: restrict delayed work to global
 wqs

On 11/13/25 2:01 AM, Alice Ryhl wrote:
> When a workqueue is shut down, delayed work that is pending but not
> scheduled does not get properly cleaned up, so it's not safe to use
> `enqueue_delayed` on a workqueue that might be destroyed. To fix this,
> restricted `enqueue_delayed` to static queues.
> 
> Signed-off-by: Alice Ryhl <aliceryhl@...gle.com>
> ---
>  rust/kernel/workqueue.rs | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/rust/kernel/workqueue.rs b/rust/kernel/workqueue.rs
> index 706e833e9702ba4ba9aa7756b0e1fa80079a63fc..901102a8bca54c9fb58655d80fc9624b4dfe1dc1 100644
> --- a/rust/kernel/workqueue.rs
> +++ b/rust/kernel/workqueue.rs
> @@ -297,7 +297,7 @@ pub fn enqueue<W, const ID: u64>(&self, w: W) -> W::EnqueueOutput
>      /// This may fail if the work item is already enqueued in a workqueue.
>      ///
>      /// The work item will be submitted using `WORK_CPU_UNBOUND`.
> -    pub fn enqueue_delayed<W, const ID: u64>(&self, w: W, delay: Jiffies) -> W::EnqueueOutput
> +    pub fn enqueue_delayed<W, const ID: u64>(&'static self, w: W, delay: Jiffies) -> W::EnqueueOutput

Hi Alice,

Looks good, just a documentation suggestion below.

Reviewed-by: John Hubbard <jhubbard@...dia.com>


I think it deserves a documentation comment (even though patch 2/2
has not yet arrived, we can still document this accurately), for example:

diff --git a/rust/kernel/workqueue.rs b/rust/kernel/workqueue.rs
index 313d897fe93c..9e55d68f3b0d 100644
--- a/rust/kernel/workqueue.rs
+++ b/rust/kernel/workqueue.rs
@@ -299,6 +299,8 @@ pub fn enqueue<W, const ID: u64>(&self, w: W) -> W::EnqueueOutput
     /// Enqueues a delayed work item.
     ///
     /// This may fail if the work item is already enqueued in a workqueue.
+    /// This is only valid for global workqueues (with static lifetimes) because those are the only
+    /// ones that outlive all possible delayed work items.
     ///
     /// The work item will be submitted using `WORK_CPU_UNBOUND`.
     pub fn enqueue_delayed<W, const ID: u64>(&'static self, w: W, delay: Jiffies) -> W::EnqueueOutput


Also, rustfmt (1.8.0-stable) split the changed line for me, upon
saving the file, I'm not sure if it will do that for everyone. Just
a heads up.


thanks,
-- 
John Hubbard