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[2620:137:e000::1:20]) by mx.google.com with ESMTP id g1-20020a17090a828100b0023b340b6388si1711929pjn.97.2023.04.05.11.02.14; Wed, 05 Apr 2023 11:02:38 -0700 (PDT) Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20; Authentication-Results: mx.google.com; dkim=pass header.i=@gmail.com header.s=20210112 header.b=U8A1YMhx; spf=pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org; dmarc=pass (p=NONE sp=QUARANTINE dis=NONE) header.from=gmail.com Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231311AbjDERv5 (ORCPT + 99 others); Wed, 5 Apr 2023 13:51:57 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:38118 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229544AbjDERvx (ORCPT ); Wed, 5 Apr 2023 13:51:53 -0400 Received: from mail-oi1-x22f.google.com (mail-oi1-x22f.google.com [IPv6:2607:f8b0:4864:20::22f]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id C79A565A6; Wed, 5 Apr 2023 10:51:51 -0700 (PDT) Received: by mail-oi1-x22f.google.com with SMTP id q27so26502839oiw.0; Wed, 05 Apr 2023 10:51:51 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20210112; t=1680717111; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:from:to:cc:subject:date :message-id:reply-to; bh=h4CtoUCbfJKvJDUejPnqVKPbox3V5JpU7mD+YHnrxrI=; b=U8A1YMhx9n67wS6QvN2LO5fauGQUWgbFZIQk29wT51pdEiDN2+nLR1vN1KvLhK9y1c GPve1WrCx5ywrc4QDsiSj+4B42uHyfKzJ+XeSH0E8AWTKnZb5MyEE6OCWbG5jynVL7Bm eomN0l9hDgpqLHgC4Olj8JN+lHMXN5ARivBHdNn+v6hjCdP32gJWZuP3hn/+CZOoT0rU UwGUR9Osi91eqVDJMb+s9a+D4qh2K3o1iue9ia/jUUmztMhUio2R1d7+7VyC7RuYoS0A ksByHVle3X+WYRpCVhHlp4jmMdAkD/Y8/2DO+3F28wR+m8w8oS4zQr4TkHYioCcIsLIH GoiA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; t=1680717111; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:x-gm-message-state:from:to:cc :subject:date:message-id:reply-to; bh=h4CtoUCbfJKvJDUejPnqVKPbox3V5JpU7mD+YHnrxrI=; b=nFmdwOlMnLoExYQvBcK1kVaHdgJKXpYWyU/o6ZCOCBJwep2HAoedfpfWgwzqv6tyEd lrUxeq1PRBLsu7ejboCAI3RKdqA/gFQYLTR/Jzy/m2C46xPtHLXHgjj97mZ6mP5auK3u WVWGaSctZN3QQHGJLwZ1NS9a/FwLQ9bmv+Ot1rjHPnarLCKoalm6H+5bo/W80qVeAquo TCgchCAQYEnAFv+vpp53EfW8o4xPSZzL7zjJxC+A44AtwI9At9eNgs/sgJs9mlCXh6cV 7MrYlVSCxGz//aZPPSosdSk3lbRKRwvFKoaX5RB14EpdvSQTPwuXGk+pAAK7A64o30gM W6yQ== X-Gm-Message-State: AAQBX9fr4x66hN8XZNYGiMULu12jGjlG4WbqUoUqY7mEQ4pjVaH0Cqvx Y9qvZtkkiHMvfjfGsWTmomKJcp3AbLhUnw== X-Received: by 2002:aca:221a:0:b0:389:888a:73b9 with SMTP id b26-20020aca221a000000b00389888a73b9mr1323517oic.28.1680717110798; Wed, 05 Apr 2023 10:51:50 -0700 (PDT) Received: from wedsonaf-dev.home.lan ([189.124.190.154]) by smtp.googlemail.com with ESMTPSA id w185-20020aca62c2000000b003896e31867esm6604045oib.49.2023.04.05.10.51.47 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 05 Apr 2023 10:51:50 -0700 (PDT) From: Wedson Almeida Filho To: rust-for-linux@vger.kernel.org Cc: Miguel Ojeda , Alex Gaynor , Boqun Feng , Gary Guo , =?utf-8?q?B?= =?utf-8?q?j=C3=B6rn_Roy_Baron?= , linux-kernel@vger.kernel.org, Wedson Almeida Filho Subject: [PATCH v2 02/13] rust: sync: introduce `Lock` and `Guard` Date: Wed, 5 Apr 2023 14:51:00 -0300 Message-Id: <20230405175111.5974-2-wedsonaf@gmail.com> X-Mailer: git-send-email 2.34.1 In-Reply-To: <20230405175111.5974-1-wedsonaf@gmail.com> References: <20230405175111.5974-1-wedsonaf@gmail.com> MIME-Version: 1.0 X-Spam-Status: No, score=-0.2 required=5.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,DKIM_VALID_EF,FREEMAIL_FROM,RCVD_IN_DNSWL_NONE, SPF_HELO_NONE,SPF_PASS autolearn=unavailable autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on lindbergh.monkeyblade.net Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org X-getmail-retrieved-from-mailbox: =?utf-8?q?INBOX?= X-GMAIL-THRID: =?utf-8?q?1762360304008760580?= X-GMAIL-MSGID: =?utf-8?q?1762360304008760580?= From: Wedson Almeida Filho They are generic Rust implementations of a lock and a lock guard that contain code that is common to all locks. Different backends will be introduced in subsequent commits. Suggested-by: Gary Guo Signed-off-by: Wedson Almeida Filho --- v1 -> v2: No changes rust/kernel/sync.rs | 2 +- rust/kernel/sync/lock.rs | 160 +++++++++++++++++++++++++++++++++++++++ 2 files changed, 161 insertions(+), 1 deletion(-) create mode 100644 rust/kernel/sync/lock.rs diff --git a/rust/kernel/sync.rs b/rust/kernel/sync.rs index 84a4b560828c..bf088b324af4 100644 --- a/rust/kernel/sync.rs +++ b/rust/kernel/sync.rs @@ -8,6 +8,7 @@ use crate::types::Opaque; mod arc; +pub mod lock; pub use arc::{Arc, ArcBorrow, UniqueArc}; @@ -25,7 +26,6 @@ impl LockClassKey { Self(Opaque::uninit()) } - #[allow(dead_code)] pub(crate) fn as_ptr(&self) -> *mut bindings::lock_class_key { self.0.get() } diff --git a/rust/kernel/sync/lock.rs b/rust/kernel/sync/lock.rs new file mode 100644 index 000000000000..f5614bed2a78 --- /dev/null +++ b/rust/kernel/sync/lock.rs @@ -0,0 +1,160 @@ +// SPDX-License-Identifier: GPL-2.0 + +//! Generic kernel lock and guard. +//! +//! It contains a generic Rust lock and guard that allow for different backends (e.g., mutexes, +//! spinlocks, raw spinlocks) to be provided with minimal effort. + +use super::LockClassKey; +use crate::{bindings, init::PinInit, pin_init, str::CStr, types::Opaque}; +use core::{cell::UnsafeCell, marker::PhantomData, marker::PhantomPinned}; +use macros::pin_data; + +/// The "backend" of a lock. +/// +/// It is the actual implementation of the lock, without the need to repeat patterns used in all +/// locks. +/// +/// # Safety +/// +/// - Implementers must ensure that only one thread/CPU may access the protected data once the lock +/// is owned, that is, between calls to `lock` and `unlock`. +pub unsafe trait Backend { + /// The state required by the lock. + type State; + + /// The state required to be kept between lock and unlock. + type GuardState; + + /// Initialises the lock. + /// + /// # Safety + /// + /// `ptr` must be valid for write for the duration of the call, while `name` and `key` must + /// remain valid for read indefinitely. + unsafe fn init( + ptr: *mut Self::State, + name: *const core::ffi::c_char, + key: *mut bindings::lock_class_key, + ); + + /// Acquires the lock, making the caller its owner. + /// + /// # Safety + /// + /// Callers must ensure that [`Backend::init`] has been previously called. + #[must_use] + unsafe fn lock(ptr: *mut Self::State) -> Self::GuardState; + + /// Releases the lock, giving up its ownership. + /// + /// # Safety + /// + /// It must only be called by the current owner of the lock. + unsafe fn unlock(ptr: *mut Self::State, guard_state: &Self::GuardState); +} + +/// A mutual exclusion primitive. +/// +/// Exposes one of the kernel locking primitives. Which one is exposed depends on the lock banckend +/// specified as the generic parameter `T`. +#[pin_data] +pub struct Lock { + /// The kernel lock object. + #[pin] + state: Opaque, + + /// Some locks are known to be self-referential (e.g., mutexes), while others are architecture + /// or config defined (e.g., spinlocks). So we conservatively require them to be pinned in case + /// some architecture uses self-references now or in the future. + #[pin] + _pin: PhantomPinned, + + /// The data protected by the lock. + data: UnsafeCell, +} + +// SAFETY: `Lock` can be transferred across thread boundaries iff the data it protects can. +unsafe impl Send for Lock {} + +// SAFETY: `Lock` serialises the interior mutability it provides, so it is `Sync` as long as the +// data it protects is `Send`. +unsafe impl Sync for Lock {} + +impl Lock { + /// Constructs a new lock initialiser. + #[allow(clippy::new_ret_no_self)] + pub fn new(t: T, name: &'static CStr, key: &'static LockClassKey) -> impl PinInit { + pin_init!(Self { + data: UnsafeCell::new(t), + _pin: PhantomPinned, + // SAFETY: `B::init` initialises the lock state, and both `name` and `key` have static + // lifetimes so they live indefinitely. + state <- unsafe { Opaque::manual_init2(B::init, name.as_char_ptr(), key.as_ptr()) }, + }) + } +} + +impl Lock { + /// Acquires the lock and gives the caller access to the data protected by it. + pub fn lock(&self) -> Guard<'_, T, B> { + // SAFETY: The constructor of the type calls `init`, so the existence of the object proves + // that `init` was called. + let state = unsafe { B::lock(self.state.get()) }; + // SAFETY: The lock was just acquired. + unsafe { Guard::new(self, state) } + } +} + +/// A lock guard. +/// +/// Allows mutual exclusion primitives that implement the `Backend` trait to automatically unlock +/// when a guard goes out of scope. It also provides a safe and convenient way to access the data +/// protected by the lock. +#[must_use = "the lock unlocks immediately when the guard is unused"] +pub struct Guard<'a, T: ?Sized, B: Backend> { + pub(crate) lock: &'a Lock, + pub(crate) state: B::GuardState, + _not_send: PhantomData<*mut ()>, +} + +// SAFETY: `Guard` is sync when the data protected by the lock is also sync. +unsafe impl Sync for Guard<'_, T, B> {} + +impl core::ops::Deref for Guard<'_, T, B> { + type Target = T; + + fn deref(&self) -> &Self::Target { + // SAFETY: The caller owns the lock, so it is safe to deref the protected data. + unsafe { &*self.lock.data.get() } + } +} + +impl core::ops::DerefMut for Guard<'_, T, B> { + fn deref_mut(&mut self) -> &mut Self::Target { + // SAFETY: The caller owns the lock, so it is safe to deref the protected data. + unsafe { &mut *self.lock.data.get() } + } +} + +impl Drop for Guard<'_, T, B> { + fn drop(&mut self) { + // SAFETY: The caller owns the lock, so it is safe to unlock it. + unsafe { B::unlock(self.lock.state.get(), &self.state) }; + } +} + +impl<'a, T: ?Sized, B: Backend> Guard<'a, T, B> { + /// Constructs a new immutable lock guard. + /// + /// # Safety + /// + /// The caller must ensure that it owns the lock. + pub(crate) unsafe fn new(lock: &'a Lock, state: B::GuardState) -> Self { + Self { + lock, + state, + _not_send: PhantomData, + } + } +}