On Fri, Nov 1, 2024 at 7:03 AM Boqun Feng <boqun.feng@xxxxxxxxx> wrote: > > Preparation for generic atomic implementation. To unify the > ipmlementation of a generic method over `i32` and `i64`, the C side > atomic methods need to be grouped so that in a generic method, they can > be referred as <type>::<method>, otherwise their parameters and return > value are different between `i32` and `i64`, which would require using > `transmute()` to unify the type into a `T`. > > Introduce `AtomicIpml` to represent a basic type in Rust that has the > direct mapping to an atomic implementation from C. This trait is sealed, > and currently only `i32` and `i64` ipml this. There seems to be quite a few instances of "impl" spelled as "ipml" here. > Further, different methods are put into different `*Ops` trait groups, > and this is for the future when smaller types like `i8`/`i16` are > supported but only with a limited set of API (e.g. only set(), load(), > xchg() and cmpxchg(), no add() or sub() etc). > > While the atomic mod is introduced, documentation is also added for > memory models and data races. > > Also bump my role to the maintainer of ATOMIC INFRASTRUCTURE to reflect > my responsiblity on the Rust atomic mod. > > Signed-off-by: Boqun Feng <boqun.feng@xxxxxxxxx> > --- > MAINTAINERS | 4 +- > rust/kernel/sync.rs | 1 + > rust/kernel/sync/atomic.rs | 19 ++++ > rust/kernel/sync/atomic/ops.rs | 199 +++++++++++++++++++++++++++++++++ > 4 files changed, 222 insertions(+), 1 deletion(-) > create mode 100644 rust/kernel/sync/atomic.rs > create mode 100644 rust/kernel/sync/atomic/ops.rs > > diff --git a/MAINTAINERS b/MAINTAINERS > index b77f4495dcf4..e09471027a63 100644 > --- a/MAINTAINERS > +++ b/MAINTAINERS > @@ -3635,7 +3635,7 @@ F: drivers/input/touchscreen/atmel_mxt_ts.c > ATOMIC INFRASTRUCTURE > M: Will Deacon <will@xxxxxxxxxx> > M: Peter Zijlstra <peterz@xxxxxxxxxxxxx> > -R: Boqun Feng <boqun.feng@xxxxxxxxx> > +M: Boqun Feng <boqun.feng@xxxxxxxxx> > R: Mark Rutland <mark.rutland@xxxxxxx> > L: linux-kernel@xxxxxxxxxxxxxxx > S: Maintained > @@ -3644,6 +3644,8 @@ F: arch/*/include/asm/atomic*.h > F: include/*/atomic*.h > F: include/linux/refcount.h > F: scripts/atomic/ > +F: rust/kernel/sync/atomic.rs > +F: rust/kernel/sync/atomic/ This is why mod.rs files are superior :) > @@ -0,0 +1,19 @@ > +// SPDX-License-Identifier: GPL-2.0 > + > +//! Atomic primitives. > +//! > +//! These primitives have the same semantics as their C counterparts: and the precise definitions of > +//! semantics can be found at [`LKMM`]. Note that Linux Kernel Memory (Consistency) Model is the > +//! only model for Rust code in kernel, and Rust's own atomics should be avoided. > +//! > +//! # Data races > +//! > +//! [`LKMM`] atomics have different rules regarding data races: > +//! > +//! - A normal read doesn't data-race with an atomic read. This was fixed: https://github.com/rust-lang/rust/pull/128778 > +mod private { > + /// Sealed trait marker to disable customized impls on atomic implementation traits. > + pub trait Sealed {} > +} Just make the trait unsafe? Alice
