From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-43171.protonmail.ch (mail-43171.protonmail.ch [185.70.43.171]) (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 356A241A921 for ; Mon, 12 Oct 2026 10:27:35 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=185.70.43.171 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1791800867; cv=none; b=oOsPhuxU0LWBE8mc0TjyAvywjPh0Gd13lB9b+qpx5Gnf1Us96Mofi6Mr/aEvDpMhrI2wUkCJFlsHjEJF8kxmFasXPMdyqrpLEvvJzZdJn9W0kf0x8S6jhkNwgsNmtpSVORXXJabIy8r4GZrYgOFx1Cllpew1MmzbPBSr7uXNt34= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1791800867; c=relaxed/simple; bh=9ktQ04XQBusBFJi/OLVcGAVoSpYMQy/d9WpKGQg/+RI=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version:Content-Type; b=GsOjdWGyfVdKImq95rd80DYJ6kQXqlatE+6TdV5/h7/OrINXYjasvMIqOcXPz7ESZhQU+YGXbSbIWzdwtbHtuosHSWKc727CfqpAwM3nQZX4lxklhkyi8b/ebttuftHAx03siN+utXxr0Zk/Dc4CFc5BBavO36Eix4OPHAc4KAs= 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=k3BS+8Td; arc=none smtp.client-ip=185.70.43.171 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="k3BS+8Td" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=onurozkan.dev; s=protonmail2; t=1791800853; x=1792060053; bh=mQsxZODk7maw0VbrpMztKmx4BTU7bZ7j4XxhQYj9bVA=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References:From:To: Cc:Date:Subject:Reply-To:Feedback-ID:Message-ID:BIMI-Selector; b=k3BS+8TdhZI2GMQ/QUVOho6GCK0vW3pS6p5JGS5+aqMRBPJBCuI3oOjhoSzDhI6sP R/FFmPMTNjNODcCKmc/+IT7+ny8RzDH7deaXEXeaftCVgFhSWmfbvqEsIGp/IDZq9/ 8Yi3xq2gADL7QIEP0I1H1I1l0JKdTe7z7IszZAWOCuwTHg2jZtpH9Abc9ZQWpfYEtd rmMRQ9x4J4nkqkYOxwC30hzRD0rd+bSmkoAL0CK38b+HsDlo0JhBBFeNfplzGp1Fyw Dd15dqHcG9b+DlFxCzhJsehiTVIV9sO5fHYOzp4eam4JP51RwQHqPMfyiUmeY7VuG+ X4J7yG1viZieA== X-Pm-Submission-Id: 4j3DDf6gGQz2ScXF From: =?UTF-8?q?Onur=20=C3=96zkan?= To: rust-for-linux@vger.kernel.org Cc: =?UTF-8?q?Onur=20=C3=96zkan?= , 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 Subject: [PATCH v12 3/6] rust: implement Class for ww_class support Date: Mon, 12 Oct 2026 13:26:30 +0300 Message-ID: X-Mailer: git-send-email 2.51.2 In-Reply-To: References: 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 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_ww_class and define_wd_class macros for safely declaring static instances. Reviewed-by: Alice Ryhl Reviewed-by: Daniel Almeida Signed-off-by: Onur Özkan --- rust/kernel/sync/lock.rs | 1 + rust/kernel/sync/lock/ww_mutex.rs | 7 ++ rust/kernel/sync/lock/ww_mutex/class.rs | 151 ++++++++++++++++++++++++ 3 files changed, 159 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 10b6b5e9b024f..f509250822c55 100644 --- a/rust/kernel/sync/lock.rs +++ b/rust/kernel/sync/lock.rs @@ -15,6 +15,7 @@ pub mod mutex; pub mod spinlock; +pub mod ww_mutex; pub(super) mod global; pub use global::{GlobalGuard, GlobalLock, GlobalLockBackend, GlobalLockedBy}; diff --git a/rust/kernel/sync/lock/ww_mutex.rs b/rust/kernel/sync/lock/ww_mutex.rs new file mode 100644 index 0000000000000..727c51cc73af8 --- /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/lock/ww_mutex/class.rs new file mode 100644 index 0000000000000..58a4467552700 --- /dev/null +++ b/rust/kernel/sync/lock/ww_mutex/class.rs @@ -0,0 +1,151 @@ +// 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-wait +//! or wait-die). +//! +//! The [`define_ww_class!`] and [`define_wd_class!`] macros provide safe +//! ways to create classes. + +use crate::{ + bindings, + prelude::*, + 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) => { + static $name: $crate::sync::lock::ww_mutex::Class = + // SAFETY: This is `static`, so address is fixed and won't move. + unsafe { + $crate::sync::lock::ww_mutex::Class::new_unpinned( + $crate::c_str!(::core::concat!(::core::stringify!($name), "_acquire")), + $crate::c_str!(::core::concat!(::core::stringify!($name), "_mutex")), + 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) => { + static $name: $crate::sync::lock::ww_mutex::Class = + // SAFETY: This is `static`, so address is fixed and won't move. + unsafe { + $crate::sync::lock::ww_mutex::Class::new_unpinned( + $crate::c_str!(::core::concat!(::core::stringify!($name), "_acquire")), + $crate::c_str!(::core::concat!(::core::stringify!($name), "_mutex")), + 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_wd_class, +/// define_ww_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 it. + /// 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( + acquire_name: &'static CStr, + mutex_name: &'static CStr, + is_wait_die: bool, + ) -> Self { + Class { + inner: Opaque::new(bindings::ww_class { + stamp: bindings::atomic_long_t { counter: 0 }, + acquire_name: crate::str::as_char_ptr_in_const_context(acquire_name), + mutex_name: crate::str::as_char_ptr_in_const_context(mutex_name), + 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 with + // `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 with + // `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`. + #[inline] + pub const unsafe fn from_raw<'a>(ptr: *mut bindings::ww_class) -> &'a Self { + // SAFETY: By the safety contract, `ptr` is valid to construct `Class`. + unsafe { &*ptr.cast() } + } +} + +// SAFETY: [`Class`] is immutable except for its atomic stamp. 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 other threads. +unsafe impl Send for Class {} -- 2.51.2