rust: irq: add `'static` bounds to irq callbacks

[PATCH] rust: irq: add `'static` bounds to irq callbacks

Posted by Benno Lossin 1 month, 2 weeks ago

These callback functions take a generic `T` that is used in the body as
the generic argument in `Registration` and `ThreadedRegistration`. Those
types require `T: 'static`, but due to a compiler bug this requirement
isn't propagated to the function. Thus add the bound. This was caught in
the upstream Rust CI [1].

Signed-off-by: Benno Lossin <lossin@kernel.org>
Link: https://github.com/rust-lang/rust/pull/149389 [1]
---
 rust/kernel/irq/request.rs | 12 +++++++++---
 1 file changed, 9 insertions(+), 3 deletions(-)

diff --git a/rust/kernel/irq/request.rs b/rust/kernel/irq/request.rs
index b150563fdef8..2ceeaeb0543a 100644
--- a/rust/kernel/irq/request.rs
+++ b/rust/kernel/irq/request.rs
@@ -261,7 +261,10 @@ pub fn synchronize(&self, dev: &Device<Bound>) -> Result {
 /// # Safety
 ///
 /// This function should be only used as the callback in `request_irq`.
-unsafe extern "C" fn handle_irq_callback<T: Handler>(_irq: i32, ptr: *mut c_void) -> c_uint {
+unsafe extern "C" fn handle_irq_callback<T: Handler + 'static>(
+    _irq: i32,
+    ptr: *mut c_void,
+) -> c_uint {
     // SAFETY: `ptr` is a pointer to `Registration<T>` set in `Registration::new`
     let registration = unsafe { &*(ptr as *const Registration<T>) };
     // SAFETY: The irq callback is removed before the device is unbound, so the fact that the irq
@@ -480,7 +483,7 @@ pub fn synchronize(&self, dev: &Device<Bound>) -> Result {
 /// # Safety
 ///
 /// This function should be only used as the callback in `request_threaded_irq`.
-unsafe extern "C" fn handle_threaded_irq_callback<T: ThreadedHandler>(
+unsafe extern "C" fn handle_threaded_irq_callback<T: ThreadedHandler + 'static>(
     _irq: i32,
     ptr: *mut c_void,
 ) -> c_uint {
@@ -496,7 +499,10 @@ pub fn synchronize(&self, dev: &Device<Bound>) -> Result {
 /// # Safety
 ///
 /// This function should be only used as the callback in `request_threaded_irq`.
-unsafe extern "C" fn thread_fn_callback<T: ThreadedHandler>(_irq: i32, ptr: *mut c_void) -> c_uint {
+unsafe extern "C" fn thread_fn_callback<T: ThreadedHandler + 'static>(
+    _irq: i32,
+    ptr: *mut c_void,
+) -> c_uint {
     // SAFETY: `ptr` is a pointer to `ThreadedRegistration<T>` set in `ThreadedRegistration::new`
     let registration = unsafe { &*(ptr as *const ThreadedRegistration<T>) };
     // SAFETY: The irq callback is removed before the device is unbound, so the fact that the irq

base-commit: 63804fed149a6750ffd28610c5c1c98cce6bd377
-- 
2.52.0

Re: [PATCH] rust: irq: add `'static` bounds to irq callbacks

Posted by Miguel Ojeda 1 month, 1 week ago

On Sat, Feb 14, 2026 at 10:27 AM Benno Lossin <lossin@kernel.org> wrote:
>
> These callback functions take a generic `T` that is used in the body as
> the generic argument in `Registration` and `ThreadedRegistration`. Those
> types require `T: 'static`, but due to a compiler bug this requirement
> isn't propagated to the function. Thus add the bound. This was caught in
> the upstream Rust CI [1].
>
> Signed-off-by: Benno Lossin <lossin@kernel.org>
> Link: https://github.com/rust-lang/rust/pull/149389 [1]

Applied to `rust-fixes` -- thanks everyone!

Daniel: I added your Reviewed-by from the other patch (and linked to
that patch separately too) -- I hope that is OK.

    [ The three errors looked similar and will start appearing with Rust
      1.95.0 (expected 2026-04-16). The first one was:

          error[E0310]: the parameter type `T` may not live long enough
          Error:    --> rust/kernel/irq/request.rs:266:43
              |
          266 |     let registration = unsafe { &*(ptr as *const
Registration<T>) };
              |                                           ^^^^^^^^^^^^^^^^^^^^^^
              |                                           |
              |                                           the
parameter type `T` must be valid for the static lifetime...
              |                                           ...so that
the type `T` will meet its required lifetime bounds
              |
          help: consider adding an explicit lifetime bound
              |
          264 | unsafe extern "C" fn handle_irq_callback<T: Handler +
'static>(_irq: i32, ptr: *mut c_void) -> c_uint {
              |                                                     +++++++++

        - Miguel ]

Cheers,
Miguel

Re: [PATCH] rust: irq: add `'static` bounds to irq callbacks

Posted by Danilo Krummrich 1 month, 1 week ago

On Sat Feb 14, 2026 at 10:27 AM CET, Benno Lossin wrote:
> These callback functions take a generic `T` that is used in the body as
> the generic argument in `Registration` and `ThreadedRegistration`. Those
> types require `T: 'static`, but due to a compiler bug this requirement
> isn't propagated to the function. Thus add the bound. This was caught in
> the upstream Rust CI [1].
>
> Signed-off-by: Benno Lossin <lossin@kernel.org>
> Link: https://github.com/rust-lang/rust/pull/149389 [1]

As discussed, this will go through the Rust tree -- thanks Miguel!

Acked-by: Danilo Krummrich <dakr@kernel.org>

Re: [PATCH] rust: irq: add `'static` bounds to irq callbacks

Posted by Alice Ryhl 1 month, 2 weeks ago

On Sat, Feb 14, 2026 at 10:27 AM Benno Lossin <lossin@kernel.org> wrote:
>
> These callback functions take a generic `T` that is used in the body as
> the generic argument in `Registration` and `ThreadedRegistration`. Those
> types require `T: 'static`, but due to a compiler bug this requirement
> isn't propagated to the function. Thus add the bound. This was caught in
> the upstream Rust CI [1].
>
> Signed-off-by: Benno Lossin <lossin@kernel.org>
> Link: https://github.com/rust-lang/rust/pull/149389 [1]

Would it not be a cleaner fix to just add 'static as a super-trait to
the traits directly?

trait Handler: Send + Sync + 'static {}

Alice

Re: [PATCH] rust: irq: add `'static` bounds to irq callbacks

Posted by Danilo Krummrich 1 month, 2 weeks ago

On Sat Feb 14, 2026 at 10:27 AM CET, Benno Lossin wrote:
> These callback functions take a generic `T` that is used in the body as
> the generic argument in `Registration` and `ThreadedRegistration`. Those
> types require `T: 'static`, but due to a compiler bug this requirement
> isn't propagated to the function. Thus add the bound. This was caught in
> the upstream Rust CI [1].
>
> Signed-off-by: Benno Lossin <lossin@kernel.org>
> Link: https://github.com/rust-lang/rust/pull/149389 [1]

IIUC, the current code will not compile with a fixed compiler, right?

If this is correct, this needs to be backported; I can add the Fixes: tag and
Cc: stable when I apply the patch.

- Danilo

Re: [PATCH] rust: irq: add `'static` bounds to irq callbacks

Posted by Benno Lossin 1 month, 2 weeks ago

On Sat Feb 14, 2026 at 11:23 AM CET, Danilo Krummrich wrote:
> On Sat Feb 14, 2026 at 10:27 AM CET, Benno Lossin wrote:
>> These callback functions take a generic `T` that is used in the body as
>> the generic argument in `Registration` and `ThreadedRegistration`. Those
>> types require `T: 'static`, but due to a compiler bug this requirement
>> isn't propagated to the function. Thus add the bound. This was caught in
>> the upstream Rust CI [1].
>>
>> Signed-off-by: Benno Lossin <lossin@kernel.org>
>> Link: https://github.com/rust-lang/rust/pull/149389 [1]
>
> IIUC, the current code will not compile with a fixed compiler, right?

Correct.

> If this is correct, this needs to be backported; I can add the Fixes: tag and
> Cc: stable when I apply the patch.

Oh yeah I forgot about that, good catch. I think it should be

    Fixes: 29e16fcd67ee ("rust: irq: add &Device<Bound> argument to irq callbacks")

Since that introduces the usage of the `[Threaded]Registration` types
in the function bodies.

It can also be backported further, but then it needs to be split into
threaded and non-threaded variants:

- 135d40523244 ("rust: irq: add support for threaded IRQs and handlers")
- 0851d34a8cc3 ("rust: irq: add support for non-threaded IRQs and handlers")

Cheers,
Benno

Re: [PATCH] rust: irq: add `'static` bounds to irq callbacks

Posted by Danilo Krummrich 1 month, 2 weeks ago

On Sat Feb 14, 2026 at 12:56 PM CET, Benno Lossin wrote:
> Oh yeah I forgot about that, good catch. I think it should be
>
>     Fixes: 29e16fcd67ee ("rust: irq: add &Device<Bound> argument to irq callbacks")
>
> Since that introduces the usage of the `[Threaded]Registration` types
> in the function bodies.
>
> It can also be backported further, but then it needs to be split into
> threaded and non-threaded variants:

All commits were introduced in v6.18, so technically there is no "backported
further".

But IIUC, with a fixed compiler, it also would not compile without commit
29e16fcd67ee ("rust: irq: add &Device<Bound> argument to irq callbacks"),
correct? I.e.  the two commits below are the correct Fixes: tags.

> - 135d40523244 ("rust: irq: add support for threaded IRQs and handlers")
> - 0851d34a8cc3 ("rust: irq: add support for non-threaded IRQs and handlers")

Re: [PATCH] rust: irq: add `'static` bounds to irq callbacks

Posted by Benno Lossin 1 month, 2 weeks ago

On Sat Feb 14, 2026 at 1:18 PM CET, Danilo Krummrich wrote:
> On Sat Feb 14, 2026 at 12:56 PM CET, Benno Lossin wrote:
>> Oh yeah I forgot about that, good catch. I think it should be
>>
>>     Fixes: 29e16fcd67ee ("rust: irq: add &Device<Bound> argument to irq callbacks")
>>
>> Since that introduces the usage of the `[Threaded]Registration` types
>> in the function bodies.
>>
>> It can also be backported further, but then it needs to be split into
>> threaded and non-threaded variants:
>
> All commits were introduced in v6.18, so technically there is no "backported
> further".
>
> But IIUC, with a fixed compiler, it also would not compile without commit
> 29e16fcd67ee ("rust: irq: add &Device<Bound> argument to irq callbacks"),
> correct? I.e.  the two commits below are the correct Fixes: tags.
>
>> - 135d40523244 ("rust: irq: add support for threaded IRQs and handlers")
>> - 0851d34a8cc3 ("rust: irq: add support for non-threaded IRQs and handlers")

With a fixed compiler these two would also still compile. It's just that
the callbacks will only ever be called with `T: 'static`, since that is
a bound on `[Threaded]Registration`, which stores these functions in the
C side. So from a purely no-compile-error perspective, 29e16fcd67ee is
the correct fixes. But from a "good API design" perspective, we could
choose the two other commits.

But since all commits are in v6.18, it doesn't matter all that much.

Cheers,
Benno

Re: [PATCH] rust: irq: add `'static` bounds to irq callbacks

Posted by Danilo Krummrich 1 month, 2 weeks ago

On Sat Feb 14, 2026 at 1:49 PM CET, Benno Lossin wrote:
> With a fixed compiler these two would also still compile. It's just that
> the callbacks will only ever be called with `T: 'static`, since that is
> a bound on `[Threaded]Registration`, which stores these functions in the
> C side. So from a purely no-compile-error perspective, 29e16fcd67ee is
> the correct fixes. But from a "good API design" perspective, we could
> choose the two other commits.

Makes sense, I will add

Fixes: 29e16fcd67ee ("rust: irq: add &Device<Bound> argument to irq callbacks")

then.

Thanks,
Danilo

Re: [PATCH] rust: irq: add `'static` bounds to irq callbacks

Posted by Gary Guo 1 month, 2 weeks ago

On 2026-02-14 09:27, Benno Lossin wrote:
> These callback functions take a generic `T` that is used in the body as
> the generic argument in `Registration` and `ThreadedRegistration`. Those
> types require `T: 'static`, but due to a compiler bug this requirement
> isn't propagated to the function. Thus add the bound. This was caught in
> the upstream Rust CI [1].
> 
> Signed-off-by: Benno Lossin <lossin@kernel.org>
> Link: https://github.com/rust-lang/rust/pull/149389 [1]

Reviewed-by: Gary Guo <gary@garyguo.net>

> ---
>  rust/kernel/irq/request.rs | 12 +++++++++---
>  1 file changed, 9 insertions(+), 3 deletions(-)
> 
> diff --git a/rust/kernel/irq/request.rs b/rust/kernel/irq/request.rs
> index b150563fdef8..2ceeaeb0543a 100644
> --- a/rust/kernel/irq/request.rs
> +++ b/rust/kernel/irq/request.rs
> @@ -261,7 +261,10 @@ pub fn synchronize(&self, dev: &Device<Bound>) -> Result {
>  /// # Safety
>  ///
>  /// This function should be only used as the callback in `request_irq`.
> -unsafe extern "C" fn handle_irq_callback<T: Handler>(_irq: i32, ptr: *mut c_void) -> c_uint {
> +unsafe extern "C" fn handle_irq_callback<T: Handler + 'static>(
> +    _irq: i32,
> +    ptr: *mut c_void,
> +) -> c_uint {
>      // SAFETY: `ptr` is a pointer to `Registration<T>` set in `Registration::new`
>      let registration = unsafe { &*(ptr as *const Registration<T>) };
>      // SAFETY: The irq callback is removed before the device is unbound, so the fact that the irq
> @@ -480,7 +483,7 @@ pub fn synchronize(&self, dev: &Device<Bound>) -> Result {
>  /// # Safety
>  ///
>  /// This function should be only used as the callback in `request_threaded_irq`.
> -unsafe extern "C" fn handle_threaded_irq_callback<T: ThreadedHandler>(
> +unsafe extern "C" fn handle_threaded_irq_callback<T: ThreadedHandler + 'static>(
>      _irq: i32,
>      ptr: *mut c_void,
>  ) -> c_uint {
> @@ -496,7 +499,10 @@ pub fn synchronize(&self, dev: &Device<Bound>) -> Result {
>  /// # Safety
>  ///
>  /// This function should be only used as the callback in `request_threaded_irq`.
> -unsafe extern "C" fn thread_fn_callback<T: ThreadedHandler>(_irq: i32, ptr: *mut c_void) -> c_uint {
> +unsafe extern "C" fn thread_fn_callback<T: ThreadedHandler + 'static>(
> +    _irq: i32,
> +    ptr: *mut c_void,
> +) -> c_uint {
>      // SAFETY: `ptr` is a pointer to `ThreadedRegistration<T>` set in `ThreadedRegistration::new`
>      let registration = unsafe { &*(ptr as *const ThreadedRegistration<T>) };
>      // SAFETY: The irq callback is removed before the device is unbound, so the fact that the irq
> 
> base-commit: 63804fed149a6750ffd28610c5c1c98cce6bd377