Commit 84c6d36b authored by Boqun Feng's avatar Boqun Feng Committed by Peter Zijlstra
Browse files

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



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: default avatarBoqun Feng <boqun.feng@gmail.com>
Signed-off-by: default avatarPeter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: default avatarAlice Ryhl <aliceryhl@google.com>
Reviewed-by: default avatarAndreas Hindborg <a.hindborg@kernel.org>
Reviewed-by: default avatarBenno Lossin <lossin@kernel.org>
Reviewed-by: default avatarElle Rhumsaa <elle@weathered-steel.dev>
Link: https://lore.kernel.org/all/20250719030827.61357-9-boqun.feng@gmail.com/
parent d6df37ba

rust/kernel/sync/atomic/predefine.rs

+49 −4
Original line number Diff line number Diff line
@@ -2,6 +2,9 @@ 


//! Pre-defined atomic types



use crate::static_assert;

use core::mem::{align_of, size_of};



// SAFETY: `i32` has the same size and alignment with itself, and is round-trip transmutable to

// itself.

unsafe impl super::AtomicType for i32 {
@@ -28,6 +31,35 @@ fn rhs_into_delta(rhs: i64) -> i64 { 
    }

}



// Defines an internal type that always maps to the integer type which has the same size alignment

// 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(CONFIG_64BIT))]

type isize_atomic_repr = i32;

#[allow(non_camel_case_types)]

#[cfg(CONFIG_64BIT)]

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>());

static_assert!(size_of::<usize>() == size_of::<isize_atomic_repr>());

static_assert!(align_of::<usize>() == align_of::<isize_atomic_repr>());



// SAFETY: `isize` has the same size and alignment with `isize_atomic_repr`, and is round-trip

// transmutable to `isize_atomic_repr`.

unsafe impl super::AtomicType for isize {

    type Repr = isize_atomic_repr;

}



// SAFETY: The wrapping add result of two `isize_atomic_repr`s is a valid `usize`.

unsafe impl super::AtomicAdd<isize> for isize {

    fn rhs_into_delta(rhs: isize) -> isize_atomic_repr {

        rhs as isize_atomic_repr

    }

}



// SAFETY: `u32` and `i32` has the same size and alignment, and `u32` is round-trip transmutable to

// `i32`.

unsafe impl super::AtomicType for u32 {
@@ -54,6 +86,19 @@ fn rhs_into_delta(rhs: u64) -> i64 { 
    }

}



// SAFETY: `usize` has the same size and alignment with `isize_atomic_repr`, and is round-trip

// transmutable to `isize_atomic_repr`.

unsafe impl super::AtomicType for usize {

    type Repr = isize_atomic_repr;

}



// SAFETY: The wrapping add result of two `isize_atomic_repr`s is a valid `usize`.

unsafe impl super::AtomicAdd<usize> for usize {

    fn rhs_into_delta(rhs: usize) -> isize_atomic_repr {

        rhs as isize_atomic_repr

    }

}



use crate::macros::kunit_tests;



#[kunit_tests(rust_atomics)]
@@ -73,7 +118,7 @@ macro_rules! for_each_type { 


    #[test]

    fn atomic_basic_tests() {

        for_each_type!(42 in [i32, i64, u32, u64] |v| {

        for_each_type!(42 in [i32, i64, u32, u64, isize, usize] |v| {

            let x = Atomic::new(v);



            assert_eq!(v, x.load(Relaxed));
@@ -82,7 +127,7 @@ fn atomic_basic_tests() { 


    #[test]

    fn atomic_xchg_tests() {

        for_each_type!(42 in [i32, i64, u32, u64] |v| {

        for_each_type!(42 in [i32, i64, u32, u64, isize, usize] |v| {

            let x = Atomic::new(v);



            let old = v;
@@ -95,7 +140,7 @@ fn atomic_xchg_tests() { 


    #[test]

    fn atomic_cmpxchg_tests() {

        for_each_type!(42 in [i32, i64, u32, u64] |v| {

        for_each_type!(42 in [i32, i64, u32, u64, isize, usize] |v| {

            let x = Atomic::new(v);



            let old = v;
@@ -110,7 +155,7 @@ fn atomic_cmpxchg_tests() { 


    #[test]

    fn atomic_arithmetic_tests() {

        for_each_type!(42 in [i32, i64, u32, u64] |v| {

        for_each_type!(42 in [i32, i64, u32, u64, isize, usize] |v| {

            let x = Atomic::new(v);



            assert_eq!(v, x.fetch_add(12, Full));