From: Boqun Feng <boqun.feng@gmail.com>
To: rust-for-linux@vger.kernel.org, linux-kernel@vger.kernel.org,
lkmm@lists.linux.dev
Cc: "Will Deacon" <will@kernel.org>,
"Peter Zijlstra" <peterz@infradead.org>,
"Mark Rutland" <mark.rutland@arm.com>,
"Ingo Molnar" <mingo@kernel.org>,
"Thomas Gleixner" <tglx@linutronix.de>,
"Paul E. McKenney" <paulmck@kernel.org>,
stern@rowland.harvard.edu, "Miguel Ojeda" <ojeda@kernel.org>,
alex.gaynor@gmail.com, "Gary Guo" <gary@garyguo.net>,
"Björn Roy Baron" <bjorn3_gh@protonmail.com>,
"Benno Lossin" <lossin@kernel.org>,
"Alice Ryhl" <aliceryhl@google.com>,
"Trevor Gross" <tmgross@umich.edu>,
"Danilo Krummrich" <dakr@kernel.org>,
"Andreas Hindborg" <a.hindborg@kernel.org>,
"Boqun Feng" <boqun.feng@gmail.com>
Subject: [PATCH 09/14] rust: sync: Add memory barriers
Date: Thu, 4 Sep 2025 21:41:36 -0700 [thread overview]
Message-ID: <20250905044141.77868-10-boqun.feng@gmail.com> (raw)
In-Reply-To: <20250905044141.77868-1-boqun.feng@gmail.com>
Memory barriers are building blocks for concurrent code, hence provide
a minimal set of them.
The compiler barrier, barrier(), is implemented in inline asm instead of
using core::sync::atomic::compiler_fence() because memory models are
different: kernel's atomics are implemented in inline asm therefore the
compiler barrier should be implemented in inline asm as well. Also it's
currently only public to the kernel crate until there's a reasonable
driver usage.
Reviewed-by: Alice Ryhl <aliceryhl@google.com>
Signed-off-by: Boqun Feng <boqun.feng@gmail.com>
Link: https://lore.kernel.org/all/20250719030827.61357-10-boqun.feng@gmail.com/
---
rust/helpers/barrier.c | 18 +++++++++++
rust/helpers/helpers.c | 1 +
rust/kernel/sync.rs | 1 +
rust/kernel/sync/barrier.rs | 61 +++++++++++++++++++++++++++++++++++++
4 files changed, 81 insertions(+)
create mode 100644 rust/helpers/barrier.c
create mode 100644 rust/kernel/sync/barrier.rs
diff --git a/rust/helpers/barrier.c b/rust/helpers/barrier.c
new file mode 100644
index 000000000000..cdf28ce8e511
--- /dev/null
+++ b/rust/helpers/barrier.c
@@ -0,0 +1,18 @@
+// SPDX-License-Identifier: GPL-2.0
+
+#include <asm/barrier.h>
+
+void rust_helper_smp_mb(void)
+{
+ smp_mb();
+}
+
+void rust_helper_smp_wmb(void)
+{
+ smp_wmb();
+}
+
+void rust_helper_smp_rmb(void)
+{
+ smp_rmb();
+}
diff --git a/rust/helpers/helpers.c b/rust/helpers/helpers.c
index 7053f9245759..85ad14b81925 100644
--- a/rust/helpers/helpers.c
+++ b/rust/helpers/helpers.c
@@ -9,6 +9,7 @@
#include "atomic.c"
#include "auxiliary.c"
+#include "barrier.c"
#include "blk.c"
#include "bug.c"
#include "build_assert.c"
diff --git a/rust/kernel/sync.rs b/rust/kernel/sync.rs
index 7e962e5429d2..bf8943c88a89 100644
--- a/rust/kernel/sync.rs
+++ b/rust/kernel/sync.rs
@@ -12,6 +12,7 @@
mod arc;
pub mod aref;
pub mod atomic;
+pub mod barrier;
pub mod completion;
mod condvar;
pub mod lock;
diff --git a/rust/kernel/sync/barrier.rs b/rust/kernel/sync/barrier.rs
new file mode 100644
index 000000000000..8f2d435fcd94
--- /dev/null
+++ b/rust/kernel/sync/barrier.rs
@@ -0,0 +1,61 @@
+// SPDX-License-Identifier: GPL-2.0
+
+//! Memory barriers.
+//!
+//! These primitives have the same semantics as their C counterparts: and the precise definitions
+//! of semantics can be found at [`LKMM`].
+//!
+//! [`LKMM`]: srctree/tools/memory-model/
+
+/// A compiler barrier.
+///
+/// A barrier that prevents compiler from reordering memory accesses across the barrier.
+#[inline(always)]
+pub(crate) fn barrier() {
+ // By default, Rust inline asms are treated as being able to access any memory or flags, hence
+ // it suffices as a compiler barrier.
+ //
+ // SAFETY: An empty asm block.
+ unsafe { core::arch::asm!("") };
+}
+
+/// A full memory barrier.
+///
+/// A barrier that prevents compiler and CPU from reordering memory accesses across the barrier.
+#[inline(always)]
+pub fn smp_mb() {
+ if cfg!(CONFIG_SMP) {
+ // SAFETY: `smp_mb()` is safe to call.
+ unsafe { bindings::smp_mb() };
+ } else {
+ barrier();
+ }
+}
+
+/// A write-write memory barrier.
+///
+/// A barrier that prevents compiler and CPU from reordering memory write accesses across the
+/// barrier.
+#[inline(always)]
+pub fn smp_wmb() {
+ if cfg!(CONFIG_SMP) {
+ // SAFETY: `smp_wmb()` is safe to call.
+ unsafe { bindings::smp_wmb() };
+ } else {
+ barrier();
+ }
+}
+
+/// A read-read memory barrier.
+///
+/// A barrier that prevents compiler and CPU from reordering memory read accesses across the
+/// barrier.
+#[inline(always)]
+pub fn smp_rmb() {
+ if cfg!(CONFIG_SMP) {
+ // SAFETY: `smp_rmb()` is safe to call.
+ unsafe { bindings::smp_rmb() };
+ } else {
+ barrier();
+ }
+}
--
2.51.0
next prev parent reply other threads:[~2025-09-05 4:42 UTC|newest]
Thread overview: 30+ messages / expand[flat|nested] mbox.gz Atom feed top
2025-09-05 4:41 [GIT PULL] [PATCH 00/14] Rust atomic changes for v6.18 Boqun Feng
2025-09-05 4:41 ` [PATCH 01/14] rust: Introduce atomic API helpers Boqun Feng
2025-09-06 4:22 ` Elle Rhumsaa
2025-09-05 4:41 ` [PATCH 02/14] rust: sync: Add basic atomic operation mapping framework Boqun Feng
2025-09-06 4:22 ` Elle Rhumsaa
2025-09-05 4:41 ` [PATCH 03/14] rust: sync: atomic: Add ordering annotation types Boqun Feng
2025-09-06 4:22 ` Elle Rhumsaa
2025-09-05 4:41 ` [PATCH 04/14] rust: sync: atomic: Add generic atomics Boqun Feng
2025-09-06 4:23 ` Elle Rhumsaa
2025-09-05 4:41 ` [PATCH 05/14] rust: sync: atomic: Add atomic {cmp,}xchg operations Boqun Feng
2025-09-06 4:23 ` Elle Rhumsaa
2025-09-05 4:41 ` [PATCH 06/14] rust: sync: atomic: Add the framework of arithmetic operations Boqun Feng
2025-09-06 4:23 ` Elle Rhumsaa
2025-09-05 4:41 ` [PATCH 07/14] rust: sync: atomic: Add Atomic<u{32,64}> Boqun Feng
2025-09-06 4:24 ` Elle Rhumsaa
2025-09-05 4:41 ` [PATCH 08/14] rust: sync: atomic: Add Atomic<{usize,isize}> Boqun Feng
2025-09-06 4:24 ` Elle Rhumsaa
2025-09-05 4:41 ` Boqun Feng [this message]
2025-09-06 4:25 ` [PATCH 09/14] rust: sync: Add memory barriers Elle Rhumsaa
2025-09-05 4:41 ` [PATCH 10/14] rust: implement `kernel::sync::Refcount` Boqun Feng
2025-09-06 4:25 ` Elle Rhumsaa
2025-09-05 4:41 ` [PATCH 11/14] rust: make `Arc::into_unique_or_drop` associated function Boqun Feng
2025-09-06 4:25 ` Elle Rhumsaa
2025-09-05 4:41 ` [PATCH 12/14] rust: convert `Arc` to use `Refcount` Boqun Feng
2025-09-06 4:26 ` Elle Rhumsaa
2025-09-05 4:41 ` [PATCH 13/14] rust: block: convert `block::mq` " Boqun Feng
2025-09-06 4:26 ` Elle Rhumsaa
2025-09-05 4:41 ` [PATCH 14/14] MAINTAINERS: update atomic infrastructure entry to include Rust Boqun Feng
2025-09-06 4:26 ` Elle Rhumsaa
2025-09-10 5:27 ` [GIT PULL] [PATCH 00/14] Rust atomic changes for v6.18 Boqun Feng
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