From nobody Sun Feb 8 14:10:42 2026 Received: from forward200a.mail.yandex.net (forward200a.mail.yandex.net [178.154.239.93]) (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 3F22E20C038; Fri, 2 Jan 2026 18:01:49 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=178.154.239.93 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1767376912; cv=none; b=FWZQ21ftWK180LAA5VQQezcxVqiNraKk0MCjMjtxQTl2+Fm7MOWqtwEW8BUNaB8mce1To23lfmUB62Gicz+HhwGYqRxHm14J20acJXs/ednYhQAKFU1EGLtdarKIlxCLyzkkrWOoBfn1QMJFsRhR8lG5wLEYba+5taGozlN96bQ= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1767376912; c=relaxed/simple; bh=mx1XwExiBMpwPcIDb8Bk/zFD7ucxlMXBHJ/Q5HhXBW8=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version:Content-Type; b=p3VKQzyO65QmboRo44fkdt/wg+YUO8IelwQyL3y96ILauin7TkBdREftzzKB4hlHDQNKpHN3bbMzCYGcsNBfCdjkgsi9EW2H8jLY03Jzn0KBHq+9I8rc2z71z+vnrTJT1pIUN9F6bYgWTwmQQaia5jxmtpM3rKvJ2UjqThRfcNg= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=onurozkan.dev; spf=pass smtp.mailfrom=onurozkan.dev; dkim=pass (1024-bit key) header.d=onurozkan.dev header.i=@onurozkan.dev header.b=JyAgWu8Z; arc=none smtp.client-ip=178.154.239.93 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=reject 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 (1024-bit key) header.d=onurozkan.dev header.i=@onurozkan.dev header.b="JyAgWu8Z" Received: from forward100a.mail.yandex.net (forward100a.mail.yandex.net [IPv6:2a02:6b8:c0e:500:1:45:d181:d100]) by forward200a.mail.yandex.net (Yandex) with ESMTPS id D76D9C2E9E; Fri, 02 Jan 2026 20:55:07 +0300 (MSK) Received: from mail-nwsmtp-smtp-production-main-55.vla.yp-c.yandex.net (mail-nwsmtp-smtp-production-main-55.vla.yp-c.yandex.net [IPv6:2a02:6b8:c1f:582e:0:640:200:0]) by forward100a.mail.yandex.net (Yandex) with ESMTPS id 756CCC0150; Fri, 02 Jan 2026 20:54:59 +0300 (MSK) Received: by mail-nwsmtp-smtp-production-main-55.vla.yp-c.yandex.net (smtp/Yandex) with ESMTPSA id prp9aJGHE8c0-wHYenAXA; Fri, 02 Jan 2026 20:54:58 +0300 X-Yandex-Fwd: 1 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=onurozkan.dev; s=mail; t=1767376498; bh=5h1taYK8Ik1h8HK1Vjon+hdeAv1dK1mYLr6IxPRcYGw=; h=Cc:Message-ID:References:Date:In-Reply-To:Subject:To:From; b=JyAgWu8Z/+bfGwTVQAzboWruZNH8tj7jwktdcTCisOVr6B1M9lXrXbzowQr61yXLJ mZMC3pGizEgThTk7Uc92i2YOrwqsNZwoF5T510Qq+lxnzx7EGXjrocFoRgsHBJRGlA GEvf89yX0qTJ3XMKS075LOluzK1YwBNLR2pgebtE= Authentication-Results: mail-nwsmtp-smtp-production-main-55.vla.yp-c.yandex.net; dkim=pass header.i=@onurozkan.dev From: =?UTF-8?q?Onur=20=C3=96zkan?= To: rust-for-linux@vger.kernel.org Cc: lossin@kernel.org, lyude@redhat.com, ojeda@kernel.org, alex.gaynor@gmail.com, boqun.feng@gmail.com, gary@garyguo.net, a.hindborg@kernel.org, aliceryhl@google.com, tmgross@umich.edu, dakr@kernel.org, peterz@infradead.org, mingo@redhat.com, will@kernel.org, longman@redhat.com, felipe_life@live.com, daniel@sedlak.dev, daniel.almeida@collabora.com, thomas.hellstrom@linux.intel.com, linux-kernel@vger.kernel.org, =?UTF-8?q?Onur=20=C3=96zkan?= Subject: [PATCH v9 4/7] rust: implement Class for ww_class support Date: Fri, 2 Jan 2026 20:52:59 +0300 Message-ID: <20260102175302.194435-5-work@onurozkan.dev> X-Mailer: git-send-email 2.51.2 In-Reply-To: <20260102175302.194435-1-work@onurozkan.dev> References: <20260102175302.194435-1-work@onurozkan.dev> 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: quoted-printable Adds the Class type, the first step in supporting ww_mutex in Rust. Class represents ww_class, used for deadlock avoidance for supporting both wait-die and wound-wait semantics. Also adds the define_class macro for safely declaring static instances. Signed-off-by: Onur =C3=96zkan --- rust/kernel/sync/lock.rs | 1 + rust/kernel/sync/lock/ww_mutex.rs | 7 ++ rust/kernel/sync/lock/ww_mutex/class.rs | 139 ++++++++++++++++++++++++ 3 files changed, 147 insertions(+) create mode 100644 rust/kernel/sync/lock/ww_mutex.rs create mode 100644 rust/kernel/sync/lock/ww_mutex/class.rs diff --git a/rust/kernel/sync/lock.rs b/rust/kernel/sync/lock.rs index 46a57d1fc309..ef7f4a023177 100644 --- a/rust/kernel/sync/lock.rs +++ b/rust/kernel/sync/lock.rs @@ -15,6 +15,7 @@ =20 pub mod mutex; pub mod spinlock; +pub mod ww_mutex; =20 pub(super) mod global; pub use global::{GlobalGuard, GlobalLock, GlobalLockBackend, GlobalLockedB= y}; diff --git a/rust/kernel/sync/lock/ww_mutex.rs b/rust/kernel/sync/lock/ww_m= utex.rs new file mode 100644 index 000000000000..727c51cc73af --- /dev/null +++ b/rust/kernel/sync/lock/ww_mutex.rs @@ -0,0 +1,7 @@ +// SPDX-License-Identifier: GPL-2.0 + +//! Rust abstractions for the kernel's wound-wait locking primitives. + +pub use class::Class; + +mod class; diff --git a/rust/kernel/sync/lock/ww_mutex/class.rs b/rust/kernel/sync/loc= k/ww_mutex/class.rs new file mode 100644 index 000000000000..d57478f33659 --- /dev/null +++ b/rust/kernel/sync/lock/ww_mutex/class.rs @@ -0,0 +1,139 @@ +// SPDX-License-Identifier: GPL-2.0 + +//! Provides [`Class`] to group wound/wait mutexes to be acquired together +//! and specifies which deadlock avoidance algorithm to use (e.g., wound-w= ait +//! or wait-die). +//! +//! The [`define_ww_class!`] and [`define_wd_class!`] macros provide safe +//! ways to create classes. + +use crate::bindings; +use crate::prelude::*; +use crate::types::Opaque; + +/// Defines a static wound-wait [`Class`]. +/// +/// # Examples +/// +/// ``` +/// use kernel::define_ww_class; +/// +/// define_ww_class!(SOME_WW_CLASS); +/// ``` +#[macro_export] +macro_rules! define_ww_class { + ($name:ident) =3D> { + static $name: $crate::sync::lock::ww_mutex::Class =3D + // SAFETY: This is `static`, so address is fixed and won't mov= e. + unsafe { + $crate::sync::lock::ww_mutex::Class::new_unpinned( + $crate::c_str!(::core::stringify!($name)), + false, + ) + }; + }; +} + +/// Defines a static wait-die [`Class`]. +/// +/// # Examples +/// +/// ``` +/// use kernel::define_wd_class; +/// +/// define_wd_class!(SOME_WD_CLASS); +/// ``` +#[macro_export] +macro_rules! define_wd_class { + ($name:ident) =3D> { + static $name: $crate::sync::lock::ww_mutex::Class =3D + // SAFETY: This is `static`, so address is fixed and won't mov= e. + unsafe { + $crate::sync::lock::ww_mutex::Class::new_unpinned( + $crate::c_str!(::core::stringify!($name)), + true, + ) + }; + }; +} + +/// Used to group mutexes together for deadlock avoidance. +/// +/// All mutexes that might be acquired together should use the same class. +/// +/// # Examples +/// +/// ``` +/// use kernel::{define_ww_class, define_wd_class}; +/// +/// define_ww_class!(SOME_WW_CLASS); +/// define_wd_class!(SOME_WD_CLASS); +/// +/// # Ok::<(), Error>(()) +/// ``` +#[pin_data] +#[repr(transparent)] +pub struct Class { + #[pin] + pub(super) inner: Opaque, +} + +impl Class { + /// Creates an unpinned [`Class`]. + /// + /// You should prefer using [`define_ww_class!`] and [`define_wd_class= !`] + /// macros. This function is `pub` only so that those macros can use i= t. + /// The alternative would be to expose the private fields of [`Class`] + /// which is less desirable. + /// + /// # Safety + /// + /// Caller must guarantee that the returned value must be pinned before + /// its first use. + pub const unsafe fn new_unpinned(name: &'static CStr, is_wait_die: boo= l) -> Self { + Class { + inner: Opaque::new(bindings::ww_class { + stamp: bindings::atomic_long_t { counter: 0 }, + acquire_name: name.as_ptr().cast(), + mutex_name: name.as_ptr().cast(), + is_wait_die: is_wait_die as u32, + // TODO: Replace with `bindings::lock_class_key::default()= ` once + // stabilized for `const`. + // + // SAFETY: This is always zero-initialized when defined wi= th + // `DEFINE_WD_CLASS` globally on C side. + // + // For reference, see __WW_CLASS_INITIALIZER() in + // "include/linux/ww_mutex.h". + acquire_key: unsafe { core::mem::zeroed() }, + // TODO: Replace with `bindings::lock_class_key::default()= ` once + // stabilized for `const`. + // + // SAFETY: This is always zero-initialized when defined wi= th + // `DEFINE_WD_CLASS` globally on C side. + // + // For reference, see __WW_CLASS_INITIALIZER() in + // "include/linux/ww_mutex.h". + mutex_key: unsafe { core::mem::zeroed() }, + }), + } + } + + /// Creates a [`Class`] from a raw pointer. + /// + /// This function is intended for interoperability with C code. + /// + /// # Safety + /// + /// The caller must ensure that `ptr` points to the `inner` field of + /// [`Class`] and that it remains valid for the lifetime `'a`. + pub const unsafe fn from_raw<'a>(ptr: *mut bindings::ww_class) -> &'a = Self { + // SAFETY: By the safety contract, `ptr` is valid to construct `Cl= ass`. + unsafe { &*ptr.cast() } + } +} + +// SAFETY: [`Class`] is set up once and never modified. It's fine to share= it across threads. +unsafe impl Sync for Class {} +// SAFETY: Doesn't hold anything thread-specific. It's safe to send to oth= er threads. +unsafe impl Send for Class {} --=20 2.51.2