[PATCH v4 00/10] LKMM generic atomics in Rust

[Boqun Feng <boqun.feng@gmail.com>]

Hi,

v4 for LKMM atomics in Rust, you can find the previous versions:

v3: https://lore.kernel.org/rust-for-linux/20250421164221.1121805-1-boqun.feng@gmail.com/
v2: https://lore.kernel.org/rust-for-linux/20241101060237.1185533-1-boqun.feng@gmail.com/
v1: https://lore.kernel.org/rust-for-linux/20240612223025.1158537-1-boqun.feng@gmail.com/
wip: https://lore.kernel.org/rust-for-linux/20240322233838.868874-1-boqun.feng@gmail.com/

The reason of providing our own LKMM atomics is because memory model
wise Rust native memory model is not guaranteed to work with LKMM and
having only one memory model throughout the kernel is always better for
reasoning.


I haven't gotten any review from last version but I got a few feedbacks
during Rust-for-Linux weekly meeting. I trimmed two more patches to make
the current series easier to review, the current version includes:

* Generic atomic support of i32, i64, u32, u64, isize and usize on:
  * load() and store()
  * xchg() and cmpxchg()
  * add() and fetch_add()

* Atomic pointer support on:
  * load() and store()
  * xchg() and cmpxchg()

* Barrier and ordering support.

Any missing functionality can of course be added in a later patch. There
are some use cases based on these API can be found at:

	git://git.kernel.org/pub/scm/linux/kernel/git/boqun/linux.git rust-atomic-dev

for example, RCU protected pointers and AtomicFlag.

I think the current version is ready to merge (modulo some documentation
improvement), and I would like to postpone small implementation
improvement because we are seeing growing usages of atomics in Rust
side. It's better to merge the API first so that we can clean up and
help new users.

But I do have one question about how to route the patch, basically I
have three options:

* via tip, I can send a pull request to Ingo at -rc4 or -rc5.

* via rust-next, I can send a pull request to Miguel at -rc4 or -rc5.

* via my own tree or atomic (Peter if you remember, we do have an atomic
  group in kernel.org and I can create a shared tree under that group),
  I can send a pull request to Linus for 6.17 merge window.

Please advise.

Regards,
Boqun

Boqun Feng (10):
  rust: Introduce atomic API helpers
  rust: sync: Add basic atomic operation mapping framework
  rust: sync: atomic: Add ordering annotation types
  rust: sync: atomic: Add generic atomics
  rust: sync: atomic: Add atomic {cmp,}xchg operations
  rust: sync: atomic: Add the framework of arithmetic operations
  rust: sync: atomic: Add Atomic<u{32,64}>
  rust: sync: atomic: Add Atomic<{usize,isize}>
  rust: sync: atomic: Add Atomic<*mut T>
  rust: sync: Add memory barriers

 MAINTAINERS                               |    4 +-
 rust/helpers/atomic.c                     | 1038 +++++++++++++++++++++
 rust/helpers/barrier.c                    |   18 +
 rust/helpers/helpers.c                    |    2 +
 rust/kernel/sync.rs                       |    2 +
 rust/kernel/sync/atomic.rs                |  176 ++++
 rust/kernel/sync/atomic/generic.rs        |  524 +++++++++++
 rust/kernel/sync/atomic/ops.rs            |  199 ++++
 rust/kernel/sync/atomic/ordering.rs       |   94 ++
 rust/kernel/sync/barrier.rs               |   67 ++
 scripts/atomic/gen-atomics.sh             |    1 +
 scripts/atomic/gen-rust-atomic-helpers.sh |   65 ++
 12 files changed, 2189 insertions(+), 1 deletion(-)
 create mode 100644 rust/helpers/atomic.c
 create mode 100644 rust/helpers/barrier.c
 create mode 100644 rust/kernel/sync/atomic.rs
 create mode 100644 rust/kernel/sync/atomic/generic.rs
 create mode 100644 rust/kernel/sync/atomic/ops.rs
 create mode 100644 rust/kernel/sync/atomic/ordering.rs
 create mode 100644 rust/kernel/sync/barrier.rs
 create mode 100755 scripts/atomic/gen-rust-atomic-helpers.sh

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