linux-toradex.git/rust/kernel/sync/atomic, branch v7.0-rc5

Merge tag 'locking-core-2026-02-08' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

2026-02-10T20:28:44+00:00

Pull locking updates from Ingo Molnar:
 "Lock debugging:

   - Implement compiler-driven static analysis locking context checking,
     using the upcoming Clang 22 compiler's context analysis features
     (Marco Elver)

     We removed Sparse context analysis support, because prior to
     removal even a defconfig kernel produced 1,700+ context tracking
     Sparse warnings, the overwhelming majority of which are false
     positives. On an allmodconfig kernel the number of false positive
     context tracking Sparse warnings grows to over 5,200... On the plus
     side of the balance actual locking bugs found by Sparse context
     analysis is also rather ... sparse: I found only 3 such commits in
     the last 3 years. So the rate of false positives and the
     maintenance overhead is rather high and there appears to be no
     active policy in place to achieve a zero-warnings baseline to move
     the annotations & fixers to developers who introduce new code.

     Clang context analysis is more complete and more aggressive in
     trying to find bugs, at least in principle. Plus it has a different
     model to enabling it: it's enabled subsystem by subsystem, which
     results in zero warnings on all relevant kernel builds (as far as
     our testing managed to cover it). Which allowed us to enable it by
     default, similar to other compiler warnings, with the expectation
     that there are no warnings going forward. This enforces a
     zero-warnings baseline on clang-22+ builds (Which are still limited
     in distribution, admittedly)

     Hopefully the Clang approach can lead to a more maintainable
     zero-warnings status quo and policy, with more and more subsystems
     and drivers enabling the feature. Context tracking can be enabled
     for all kernel code via WARN_CONTEXT_ANALYSIS_ALL=y (default
     disabled), but this will generate a lot of false positives.

     ( Having said that, Sparse support could still be added back,
       if anyone is interested - the removal patch is still
       relatively straightforward to revert at this stage. )

  Rust integration updates: (Alice Ryhl, Fujita Tomonori, Boqun Feng)

    - Add support for Atomic and replace most Rust native
      AtomicBool usages with Atomic

    - Clean up LockClassKey and improve its documentation

    - Add missing Send and Sync trait implementation for SetOnce

    - Make ARef Unpin as it is supposed to be

    - Add __rust_helper to a few Rust helpers as a preparation for
      helper LTO

    - Inline various lock related functions to avoid additional function
      calls

  WW mutexes:

    - Extend ww_mutex tests and other test-ww_mutex updates (John
      Stultz)

  Misc fixes and cleanups:

    - rcu: Mark lockdep_assert_rcu_helper() __always_inline (Arnd
      Bergmann)

    - locking/local_lock: Include more missing headers (Peter Zijlstra)

    - seqlock: fix scoped_seqlock_read kernel-doc (Randy Dunlap)

    - rust: sync: Replace `kernel::c_str!` with C-Strings (Tamir
      Duberstein)"

* tag 'locking-core-2026-02-08' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (90 commits)
  locking/rwlock: Fix write_trylock_irqsave() with CONFIG_INLINE_WRITE_TRYLOCK
  rcu: Mark lockdep_assert_rcu_helper() __always_inline
  compiler-context-analysis: Remove __assume_ctx_lock from initializers
  tomoyo: Use scoped init guard
  crypto: Use scoped init guard
  kcov: Use scoped init guard
  compiler-context-analysis: Introduce scoped init guards
  cleanup: Make __DEFINE_LOCK_GUARD handle commas in initializers
  seqlock: fix scoped_seqlock_read kernel-doc
  tools: Update context analysis macros in compiler_types.h
  rust: sync: Replace `kernel::c_str!` with C-Strings
  rust: sync: Inline various lock related methods
  rust: helpers: Move #define __rust_helper out of atomic.c
  rust: wait: Add __rust_helper to helpers
  rust: time: Add __rust_helper to helpers
  rust: task: Add __rust_helper to helpers
  rust: sync: Add __rust_helper to helpers
  rust: refcount: Add __rust_helper to helpers
  rust: rcu: Add __rust_helper to helpers
  rust: processor: Add __rust_helper to helpers
  ...

rust: sync: atomic: Provide stub for `rusttest` 32-bit hosts

2026-01-26T01:18:58+00:00

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::() == size_of::()', rust/kernel/sync/atomic/predefine.rs:68:1
       |
      ::: rust/kernel/sync/atomic/predefine.rs:68:1
       |
    68 | static_assert!(size_of::() == size_of::());
       | -------------------------------------------------------------------- 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@vger.kernel.org
Reviewed-by: Onur Özkan 
Acked-by: Boqun Feng 
Link: https://patch.msgid.link/20260123233432.22703-1-ojeda@kernel.org
Signed-off-by: Miguel Ojeda

rust: sync: atomic: Add atomic bool tests

2026-01-09T11:01:41+00:00

Add tests for Atomic operations.

Atomic does not fit into the existing u8/16/32/64 tests so
introduce a dedicated test for it.

Signed-off-by: FUJITA Tomonori 
Reviewed-by: Gary Guo 
Signed-off-by: Boqun Feng 
Link: https://patch.msgid.link/20260101034922.2020334-3-fujita.tomonori@gmail.com

rust: sync: atomic: Add atomic bool support via i8 representation

2026-01-09T11:01:41+00:00

Add `bool` support, `Atomic` by using `i8` as its underlying
representation.

Rust specifies that `bool` has size 1 and alignment 1 [1], so it
matches `i8` on layout; keep `static_assert!()` checks to enforce this
assumption at build time.

[boqun: Remove the unnecessary impl AtomicImpl for bool]

Link: https://doc.rust-lang.org/reference/types/boolean.html [1]
Signed-off-by: FUJITA Tomonori 
Reviewed-by: Gary Guo 
Signed-off-by: Boqun Feng 
Link: https://patch.msgid.link/20260101034922.2020334-2-fujita.tomonori@gmail.com

rust: sync: atomic: Add i8/i16 xchg and cmpxchg support

2026-01-09T11:01:41+00:00

Add atomic xchg and cmpxchg operation support for i8 and i16 types
with tests.

Note that since the current implementation of
Atomic::<{i8,i16}>::{load,store}() is READ_ONCE()/WRITE_ONCE()-based.
The atomicity between load/store and xchg/cmpxchg is only guaranteed if
the architecture has native RmW support, hence i8/i16 is currently
AtomicImpl only when CONFIG_ARCH_SUPPORTS_ATOMIC_RWM=y.

[boqun: Make i8/i16 AtomicImpl only when
CONFIG_ARCH_SUPPORTS_ATOMIC_RWM=y]

Signed-off-by: FUJITA Tomonori 
Signed-off-by: Boqun Feng 
Link: https://patch.msgid.link/20251228120546.1602275-4-fujita.tomonori@gmail.com

rust: sync: atomic: Add store_release/load_acquire tests

2026-01-09T11:01:41+00:00

Add minimum store_release/load_acquire tests.

Signed-off-by: FUJITA Tomonori 
Reviewed-by: Gary Guo 
Reviewed-by: Joel Fernandes 
Signed-off-by: Boqun Feng 
Link: https://patch.msgid.link/20251211113826.1299077-5-fujita.tomonori@gmail.com

rust: sync: atomic: Add i8/i16 load and store support

2026-01-09T11:01:41+00:00

Add atomic operation support for i8 and i16 types using volatile
read/write and smp_load_acquire/smp_store_release helpers.

[boqun: Adjust [1] to avoid introduction of
impl_atomic_only_load_and_store_ops!() in the middle]

Signed-off-by: FUJITA Tomonori 
Reviewed-by: Gary Guo 
Reviewed-by: Joel Fernandes 
Link: https://lore.kernel.org/all/20251228120546.1602275-1-fujita.tomonori@gmail.com/ [1]
Signed-off-by: Boqun Feng 
Link: https://patch.msgid.link/20251211113826.1299077-4-fujita.tomonori@gmail.com

rust: sync: atomic: Prepare AtomicOps macros for i8/i16 support

2026-01-09T11:01:41+00:00

Rework the internal AtomicOps macro plumbing to generate per-type
implementations from a mapping list.

Capture the trait definition once and reuse it for both declaration
and per-type impl expansion to reduce duplication and keep future
extensions simple.

This is a preparatory refactor for enabling i8/i16 atomics cleanly.

Signed-off-by: FUJITA Tomonori 
Signed-off-by: Boqun Feng 
Link: https://patch.msgid.link/20251228120546.1602275-2-fujita.tomonori@gmail.com

rust: sync: atomic: Add Atomic<{usize,isize}>

2025-09-15T07:38:34+00:00

Add generic atomic support for `usize` and `isize`. Note that instead of
mapping directly to `atomic_long_t`, the represention type
(`AtomicType::Repr`) is selected based on CONFIG_64BIT. This reduces
the necessity of creating `atomic_long_*` helpers, which could save
the binary size of kernel if inline helpers are not available. To do so,
an internal type `isize_atomic_repr` is defined, it's `i32` in 32bit
kernel and `i64` in 64bit kernel.

Signed-off-by: Boqun Feng 
Signed-off-by: Peter Zijlstra (Intel) 
Reviewed-by: Alice Ryhl 
Reviewed-by: Andreas Hindborg 
Reviewed-by: Benno Lossin 
Reviewed-by: Elle Rhumsaa 
Link: https://lore.kernel.org/all/20250719030827.61357-9-boqun.feng@gmail.com/

rust: sync: atomic: Add Atomic

2025-09-15T07:38:34+00:00

Add generic atomic support for basic unsigned types that have an
`AtomicImpl` with the same size and alignment.

Unit tests are added including Atomic and Atomic.

Signed-off-by: Boqun Feng 
Signed-off-by: Peter Zijlstra (Intel) 
Reviewed-by: Alice Ryhl 
Reviewed-by: Andreas Hindborg 
Reviewed-by: Benno Lossin 
Reviewed-by: Elle Rhumsaa 
Link: https://lore.kernel.org/all/20250719030827.61357-8-boqun.feng@gmail.com/