linux-kernel - Re: [PATCH] rust: sync: atomic: Provide stub for `rusttest` 32-bit hosts

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Message-ID: <20260125090421.0b09ae21@nimda>
Date: Sun, 25 Jan 2026 09:04:21 +0300
From: Onur Özkan <work@...rozkan.dev>
To: Miguel Ojeda <ojeda@...nel.org>
Cc: Will Deacon <will@...nel.org>, Peter Zijlstra <peterz@...radead.org>,
 Boqun Feng <boqun.feng@...il.com>, Mark Rutland <mark.rutland@....com>,
 Gary Guo <gary@...yguo.net>, linux-kernel@...r.kernel.org, Björn Roy Baron <bjorn3_gh@...tonmail.com>, Benno Lossin
 <lossin@...nel.org>, Andreas Hindborg <a.hindborg@...nel.org>, Alice Ryhl
 <aliceryhl@...gle.com>, Trevor Gross <tmgross@...ch.edu>, Danilo Krummrich
 <dakr@...nel.org>, rust-for-linux@...r.kernel.org, stable@...r.kernel.org
Subject: Re: [PATCH] rust: sync: atomic: Provide stub for `rusttest` 32-bit
 hosts

On Sat, 24 Jan 2026 00:34:32 +0100
Miguel Ojeda <ojeda@...nel.org> wrote:

> For arm32, on a x86_64 builder, running the `rusttest` target yields:
> 
>     error[E0080]: evaluation of constant value failed
>       --> rust/kernel/static_assert.rs:37:23
>        |
>     37 |         const _: () = ::core::assert!($condition $(,$arg)?);
>        |                       ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
> the evaluated program panicked at 'assertion failed:
> size_of::<isize>() == size_of::<isize_atomic_repr>()',
> rust/kernel/sync/atomic/predefine.rs:68:1 | :::
> rust/kernel/sync/atomic/predefine.rs:68:1 | 68 |
> static_assert!(size_of::<isize>() == size_of::<isize_atomic_repr>());
> |
> --------------------------------------------------------------------
> in this macro invocation | = note: this error originates in the macro
> `::core::assert` which comes from the expansion of the macro
> `static_assert` (in Nightly builds, run with -Z macro-backtrace for
> more info)
> 
> The reason is that `rusttest` runs on the host, so for e.g. a x86_64
> builder `isize` is 64 bits but it is not a `CONFIG_64BIT` build.
> 
> Fix it by providing a stub for `rusttest` as usual.
> 
> Fixes: 84c6d36bcaf9 ("rust: sync: atomic: Add Atomic<{usize,isize}>")
> Cc: stable@...r.kernel.org
> Signed-off-by: Miguel Ojeda <ojeda@...nel.org>
> ---
> I kept the `cfg`s separated instead of using `all` so that, when we
> get to remove this (since these tests will eventually be moved to
> KUnit), it will just be line deletions (and I find it easier to read,
> too).
> 
>  rust/kernel/sync/atomic/predefine.rs | 11 +++++++++++
>  1 file changed, 11 insertions(+)
> 
> diff --git a/rust/kernel/sync/atomic/predefine.rs
> b/rust/kernel/sync/atomic/predefine.rs index
> 45a17985cda4..0fca1ba3c2db 100644 ---
> a/rust/kernel/sync/atomic/predefine.rs +++
> b/rust/kernel/sync/atomic/predefine.rs @@ -35,12 +35,23 @@ fn
> rhs_into_delta(rhs: i64) -> i64 { // as `isize` and `usize`, and
> `isize` and `usize` are always bi-directional transmutable to //
> `isize_atomic_repr`, which also always implements `AtomicImpl`.
> #[allow(non_camel_case_types)] +#[cfg(not(testlib))]
>  #[cfg(not(CONFIG_64BIT))]
>  type isize_atomic_repr = i32;
>  #[allow(non_camel_case_types)]
> +#[cfg(not(testlib))]
>  #[cfg(CONFIG_64BIT)]
>  type isize_atomic_repr = i64;
> 
> +#[allow(non_camel_case_types)]
> +#[cfg(testlib)]
> +#[cfg(target_pointer_width = "32")]
> +type isize_atomic_repr = i32;
> +#[allow(non_camel_case_types)]
> +#[cfg(testlib)]
> +#[cfg(target_pointer_width = "64")]
> +type isize_atomic_repr = i64;
> +
>  // Ensure size and alignment requirements are checked.
>  static_assert!(size_of::<isize>() == size_of::<isize_atomic_repr>());
>  static_assert!(align_of::<isize>() ==
> align_of::<isize_atomic_repr>());
> 
> base-commit: a44bfed9df8a514962e2cb076d9c0b594caeff36
> --
> 2.52.0

Reviewed-by: Onur Özkan <work@...rozkan.dev>