From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-43170.protonmail.ch (mail-43170.protonmail.ch [185.70.43.170]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 8A09B317163 for ; Thu, 16 Apr 2026 17:18:59 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=185.70.43.170 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1776359941; cv=none; b=s5HQ0OdMo0ih9WVUzFX0rFOENa5pdSTB0TPw8AL/eMDRotIuBHpPEtSAby+AmF6GjgAux2xmnmrBi/1NuAWxoV9nYX5xukAvqXj3jfyfBHb3sI+ddas/bsBL/OzPyuA+bex6X9Frl/BlCrDd+H+WueRgTNUpeFXMkprYDLn0s5M= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1776359941; c=relaxed/simple; bh=sal4yMiAc+eT7vJjdvwQ7GQkLASexEB9wg1620xfgT0=; h=From:To:Cc:Subject:Date:Message-ID:MIME-Version:Content-Type; b=LnGinc7doJGs09xaALtUt6YYs8V24W+qGi0a16kEoc54P7TkZBLrZLiWYfD8Of8Kv1V8EIex7RSkQFDcPebKo+J88I3ljbtc/yu7JYuZeqPYJnXFtNp7ow6srHX4urD9+4/9St/iRa/jyuHvPHuiZtDWdonxeuEHgVNWZc94dOc= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=onurozkan.dev; spf=pass smtp.mailfrom=onurozkan.dev; dkim=pass (2048-bit key) header.d=onurozkan.dev header.i=@onurozkan.dev header.b=d7B7oz1N; arc=none smtp.client-ip=185.70.43.170 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=onurozkan.dev Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=onurozkan.dev Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=onurozkan.dev header.i=@onurozkan.dev header.b="d7B7oz1N" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=onurozkan.dev; s=protonmail; t=1776359931; x=1776619131; bh=kOb3PZxaEkgAoIkp3O/NYJ+mJCTYGE92nRe9BIXjXqk=; h=From:To:Cc:Subject:Date:Message-ID:From:To:Cc:Date:Subject: Reply-To:Feedback-ID:Message-ID:BIMI-Selector; b=d7B7oz1NowwsTE5SQtR3G4GIJ6Vp2eGWjbXXFF210FApWplwOVxtq9GOaPL1KN4gb ld631ts7G8edYOEuvDt2VVBWSml6LQhSLNOdjL71vYaWlelV/QIgL1I6unuu8YFZAx jadIlYGKbb9tKQLuHS/btItPhHycbv3CjFd/MlKPx4FvBIwwFQk0MpjLDVtxuuiz2E u+EhhCky50747A3BAOuFB2m29KxtU9trcMXbYxJKUme9EX39wnvhINEw1+hgS+VCfm 5NZd32AECORtjezsS1rRoBh8OfQFfDOA0ozGSkMvjM1OIJ2q6R6dPZ6uhAcSVAdOCP VXmOBWK/e9WrQ== X-Pm-Submission-Id: 4fxPqq5tLVz1DDLZ From: =?UTF-8?q?Onur=20=C3=96zkan?= To: dakr@kernel.org, aliceryhl@google.com, daniel.almeida@collabora.com, airlied@gmail.com, simona@ffwll.ch, dri-devel@lists.freedesktop.org, linux-kernel@vger.kernel.org, rust-for-linux@vger.kernel.org, jiangshanlai@gmail.com, paulmck@kernel.org, josh@joshtriplett.org, rostedt@goodmis.org Cc: =?UTF-8?q?Onur=20=C3=96zkan?= Subject: [PATCH v2 1/4] rust: add SRCU abstraction Date: Thu, 16 Apr 2026 20:18:37 +0300 Message-ID: <20260416171838.206128-1-work@onurozkan.dev> X-Mailer: git-send-email 2.51.2 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Add a Rust abstraction for sleepable RCU (SRCU), backed by srcu_struct. Provide FFI helpers and a safe wrapper with a guard-based API for read-side critical sections. Signed-off-by: Onur Özkan --- rust/helpers/helpers.c | 1 + rust/helpers/srcu.c | 18 +++++++ rust/kernel/sync.rs | 2 + rust/kernel/sync/srcu.rs | 109 +++++++++++++++++++++++++++++++++++++++ 4 files changed, 130 insertions(+) create mode 100644 rust/helpers/srcu.c create mode 100644 rust/kernel/sync/srcu.rs diff --git a/rust/helpers/helpers.c b/rust/helpers/helpers.c index 875a9788ad40..052fef89d5f0 100644 --- a/rust/helpers/helpers.c +++ b/rust/helpers/helpers.c @@ -60,6 +60,7 @@ #include "signal.c" #include "slab.c" #include "spinlock.c" +#include "srcu.c" #include "sync.c" #include "task.c" #include "time.c" diff --git a/rust/helpers/srcu.c b/rust/helpers/srcu.c new file mode 100644 index 000000000000..b372b733eb89 --- /dev/null +++ b/rust/helpers/srcu.c @@ -0,0 +1,18 @@ +// SPDX-License-Identifier: GPL-2.0 + +#include + +__rust_helper int rust_helper_init_srcu_struct(struct srcu_struct *ssp) +{ + return init_srcu_struct(ssp); +} + +__rust_helper int rust_helper_srcu_read_lock(struct srcu_struct *ssp) +{ + return srcu_read_lock(ssp); +} + +__rust_helper void rust_helper_srcu_read_unlock(struct srcu_struct *ssp, int idx) +{ + srcu_read_unlock(ssp, idx); +} \ No newline at end of file diff --git a/rust/kernel/sync.rs b/rust/kernel/sync.rs index 993dbf2caa0e..0d6a5f1300c3 100644 --- a/rust/kernel/sync.rs +++ b/rust/kernel/sync.rs @@ -21,6 +21,7 @@ pub mod rcu; mod refcount; mod set_once; +pub mod srcu; pub use arc::{Arc, ArcBorrow, UniqueArc}; pub use completion::Completion; @@ -31,6 +32,7 @@ pub use locked_by::LockedBy; pub use refcount::Refcount; pub use set_once::SetOnce; +pub use srcu::Srcu; /// Represents a lockdep class. /// diff --git a/rust/kernel/sync/srcu.rs b/rust/kernel/sync/srcu.rs new file mode 100644 index 000000000000..cf0c16248ea3 --- /dev/null +++ b/rust/kernel/sync/srcu.rs @@ -0,0 +1,109 @@ +// SPDX-License-Identifier: GPL-2.0 + +//! Sleepable read-copy update (SRCU) abstraction. +//! +//! C header: [`include/linux/srcu.h`](srctree/include/linux/srcu.h) + +use crate::{ + bindings, + error::to_result, + prelude::*, + types::{ + NotThreadSafe, + Opaque, // + }, +}; + +use pin_init::pin_data; + +/// Creates an [`Srcu`] initialiser. +#[macro_export] +macro_rules! new_srcu { + () => { + $crate::sync::Srcu::new() + }; +} + +/// Sleepable read-copy update primitive. +/// +/// SRCU readers may sleep while holding the read-side guard. +#[repr(transparent)] +#[pin_data(PinnedDrop)] +pub struct Srcu { + #[pin] + inner: Opaque, +} + +impl Srcu { + /// Creates a new SRCU instance. + pub fn new() -> impl PinInit { + try_pin_init!(Self { + inner <- Opaque::try_ffi_init(|ptr: *mut bindings::srcu_struct| { + // SAFETY: `ptr` points to valid uninitialised memory for a `srcu_struct`. + to_result(unsafe { bindings::init_srcu_struct(ptr) }) + }), + }) + } + + /// Enters an SRCU read-side critical section. + pub fn read_lock(&self) -> Guard<'_> { + // SAFETY: By the type invariants, `self.inner.get()` is a valid initialized `srcu_struct`. + let idx = unsafe { bindings::srcu_read_lock(self.inner.get()) }; + + Guard { + srcu: self, + idx, + _nts: NotThreadSafe, + } + } + + /// Waits until all pre-existing SRCU readers have completed. + pub fn synchronize(&self) { + // SAFETY: By the type invariants, `self.inner.get()` is a valid initialized `srcu_struct`. + unsafe { bindings::synchronize_srcu(self.inner.get()) }; + } + + /// Waits until all pre-existing SRCU readers have completed, expedited. + /// + /// This requests a lower-latency grace period than [`Srcu::synchronize`] typically + /// at the cost of higher system-wide overhead. Prefer [`Srcu::synchronize`] by default + /// and use this variant only when reducing reset or teardown latency is more important + /// than the extra cost. + pub fn synchronize_expedited(&self) { + // SAFETY: By the type invariants, `self.inner.get()` is a valid initialized `srcu_struct`. + unsafe { bindings::synchronize_srcu_expedited(self.inner.get()) }; + } +} + +#[pinned_drop] +impl PinnedDrop for Srcu { + fn drop(self: Pin<&mut Self>) { + // SAFETY: `self` is pinned and `inner` contains a valid initialized `srcu_struct`. + unsafe { bindings::cleanup_srcu_struct(self.as_ref().get_ref().inner.get()) }; + } +} + +// SAFETY: `srcu_struct` may be shared and used across threads. +unsafe impl Send for Srcu {} +// SAFETY: `srcu_struct` may be shared and used concurrently. +unsafe impl Sync for Srcu {} + +/// Guard for an active SRCU read-side critical section on a particular [`Srcu`]. +pub struct Guard<'a> { + srcu: &'a Srcu, + idx: core::ffi::c_int, + _nts: NotThreadSafe, +} + +impl Guard<'_> { + /// Explicitly exits the SRCU read-side critical section. + pub fn unlock(self) {} +} + +impl Drop for Guard<'_> { + fn drop(&mut self) { + // SAFETY: `Guard` is only constructible through `Srcu::read_lock()`, + // which returns a valid index for the SRCU instance. + unsafe { bindings::srcu_read_unlock(self.srcu.inner.get(), self.idx) }; + } +} -- 2.51.2