Hi, This is another RFC version of LKMM atomics in Rust, you can find the previous versions: v1: https://lore.kernel.org/rust-for-linux/20240612223025.1158537-1-boqun.feng@xxxxxxxxx/ wip: https://lore.kernel.org/rust-for-linux/20240322233838.868874-1-boqun.feng@xxxxxxxxx/ I add a few more people Cced this time, so if you're curious about why we choose to implement LKMM atomics instead of using the Rust ones, you can find some explanation: * In my Kangrejos talk: https://lwn.net/Articles/993785/ * In Linus' email: https://lore.kernel.org/rust-for-linux/CAHk-=whkQk=zq5XiMcaU3xj4v69+jyoP-y6Sywhq-TvxSSvfEA@xxxxxxxxxxxxxx/ This time, I try implementing a generic atomic type `Atomic<T>`, since Benno and Gary suggested last time, and also Rust standard library is also going to that direction [1]. Honestly, a generic atomic type is still not quite necessary for myself, but here are a few reasons that it's useful: * It's useful for type alias, for example, if you have: type c_long = isize; Then `Atomic<c_clong>` and `Atomic<isize>` is the same type, this may make FFI code (mapping a C type to a Rust type or vice versa) more readable. * In kernel, we sometimes switch atomic to percpu for better scalabity, percpu is naturally a generic type, because it can have data that is larger than machine word size. Making atomic generic ease the potential switching/refactoring. * Generic atomics provide all the functionalities that non-generic atomics could have. That said, currently "generic" is limited to a few types: the type must be the same size as atomic_t or atomic64_t, other than basic types, only #[repr(<basic types>)] struct can be used in a `Atomic<T>`. Also this is not a full feature set patchset, things like different arithmetic operations and bit operations are still missing, they can be either future work or for future versions. I included an RCU pointer implementation as one example of the usage, so a patch from Danilo is added, but I will drop it once his patch merged. This is based on today's rust-next, and I've run all kunit tests from the doc test on x86, arm64 and riscv. Feedbacks and comments are welcome! Thanks. Regards, Boqun [1]: https://github.com/rust-lang/rust/issues/130539 Boqun Feng (12): 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: atomic: Add arithmetic ops for Atomic<*mut T> rust: sync: Add memory barriers rust: sync: rcu: Add RCU protected pointer Wedson Almeida Filho (1): rust: add rcu abstraction MAINTAINERS | 4 +- rust/helpers/atomic.c | 1038 +++++++++++++++++++++ rust/helpers/helpers.c | 3 + rust/helpers/rcu.c | 13 + rust/kernel/sync.rs | 3 + rust/kernel/sync/atomic.rs | 228 +++++ rust/kernel/sync/atomic/generic.rs | 516 ++++++++++ rust/kernel/sync/atomic/ops.rs | 199 ++++ rust/kernel/sync/atomic/ordering.rs | 94 ++ rust/kernel/sync/barrier.rs | 67 ++ rust/kernel/sync/rcu.rs | 319 +++++++ scripts/atomic/gen-atomics.sh | 1 + scripts/atomic/gen-rust-atomic-helpers.sh | 65 ++ 13 files changed, 2549 insertions(+), 1 deletion(-) create mode 100644 rust/helpers/atomic.c create mode 100644 rust/helpers/rcu.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 100644 rust/kernel/sync/rcu.rs create mode 100755 scripts/atomic/gen-rust-atomic-helpers.sh -- 2.45.2
