* Re: [PATCH 6.18 445/583] rust: devres: fix race condition due to nesting
[not found] <20260909134253.387396612@linuxfoundation.org>
@ 2026-09-10 1:03 ` Miguel Ojeda
2026-09-10 13:40 ` Sasha Levin
0 siblings, 1 reply; 2+ messages in thread
From: Miguel Ojeda @ 2026-09-10 1:03 UTC (permalink / raw)
To: gregkh
Cc: aliceryhl, boris.brezillon, dakr, markus.probst, patches, sashal,
stable, Rafael J. Wysocki, driver-core
On Wed, 09 Sep 2026 15:42:10 +0200 Greg Kroah-Hartman <gregkh@linuxfoundation.org> wrote:
>
> - try_pin_init!(&this in Self {
> + let callback = Self::devres_callback;
> + let inner = Arc::pin_init(
> + try_pin_init!(Inner {
> + data <- Revocable::new(data),
> + }),
> + GFP_KERNEL,
> + )?;
> + let devres_inner = inner.clone();
The compiler complains here:
error[E0277]: the trait bound `impl pin_init::PinInit<Inner<T>, error::Error>: pin_init::PinInit<_, E>` is not satisfied
--> rust/kernel/devres.rs:141:13
|
140 | let inner = Arc::pin_init(
| ------------- required by a bound introduced by this call
141 | / try_pin_init!(Inner {
142 | | data <- Revocable::new(data),
143 | | revocation <- Completion::new(),
144 | | }),
| | ^
| | |
| |______________the trait `pin_init::PinInit<_, E>` is not implemented for `impl pin_init::PinInit<Inner<T>, error::Error>`
| this tail expression is of type `impl PinInit<Inner<T>, Error>`
|
= help: the following other types implement trait `pin_init::PinInit<T, E>`:
<AlwaysFail<T> as pin_init::PinInit<T, ()>>
<ChainPinInit<I, F, T, E> as pin_init::PinInit<T, E>>
<ChainInit<I, F, T, E> as pin_init::PinInit<T, E>>
<core::result::Result<T, E> as pin_init::PinInit<T, E>>
note: required by a bound in `init::InPlaceInit::pin_init`
--> rust/kernel/init.rs:155:31
|
155 | fn pin_init<E>(init: impl PinInit<T, E>, flags: Flags) -> error::Result<Self::PinnedSelf>
| ^^^^^^^^^^^^^ required by this bound in `InPlaceInit::pin_init`
error[E0282]: type annotations needed for `Arc<T>`
--> rust/kernel/devres.rs:140:13
|
140 | let inner = Arc::pin_init(
| ^^^^^
...
147 | let devres_inner = inner.clone();
| ----- type must be known at this point
|
help: consider giving `inner` an explicit type, where the type for type parameter `T` is specified
|
140 | let inner: Arc<T> = Arc::pin_init(
| ++++++++
error[E0282]: type annotations needed
--> rust/kernel/devres.rs:158:17
|
158 | Arc::as_ptr(&inner).cast_mut().cast(),
| ^^^^^^^^^^^ -------- type must be known at this point
| |
| cannot infer type of the type parameter `T` declared on the struct `Arc`
|
help: consider specifying the generic argument
|
158 | Arc::<T>::as_ptr(&inner).cast_mut().cast(),
| +++++
This diff would work, similar to commit 9aa64d2503c6 ("rust: devres:
embed struct devres_node directly"), but I wonder if the sequence of
backports was not intended like this:
diff --git a/rust/kernel/devres.rs b/rust/kernel/devres.rs
index 67471946f2b5..0cafe7ba28c8 100644
--- a/rust/kernel/devres.rs
+++ b/rust/kernel/devres.rs
@@ -137,7 +137,7 @@ pub fn new<E>(dev: &Device<Bound>, data: impl PinInit<T, E>) -> Result<Self>
Error: From<E>,
{
let callback = Self::devres_callback;
- let inner = Arc::pin_init(
+ let inner = Arc::pin_init::<Error>(
try_pin_init!(Inner {
data <- Revocable::new(data),
revocation <- Completion::new(),
I hope that helps!
Cc: Markus Probst <markus.probst@posteo.de>
Cc: Sasha Levin <sashal@kernel.org>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Alice Ryhl <aliceryhl@google.com>
Cc: Boris Brezillon <boris.brezillon@collabora.com>
Cc: Danilo Krummrich <dakr@kernel.org>
Cc: "Rafael J. Wysocki" <rafael@kernel.org>
Cc: driver-core@lists.linux.dev
Cheers,
Miguel
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