From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.129.124]) (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 0D264217F34 for ; Tue, 27 May 2025 22:23:50 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=170.10.129.124 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1748384632; cv=none; b=qi+T1IiUFhndU6NQi9hx/93wDQ9lQgTQesjD9GRuC2D0vGhSItbbfFSILF90rQIjDkU3XcPH6lNTqgTHW58bkxZ4633ASpNB83TCyg/licL23hl8fn3b2NM8+JiX9nW1WhLhZxcnaMtrYrfohAJbToQvfWdv/TCruBKcMnBFUdc= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1748384632; c=relaxed/simple; bh=ePu8BVwWz4CcP33RkJL//NtqsBk8F8/EH3/wsjdTZOg=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=SmAQNtCKMIvcq9Jlbt30C7G42VVy5L1QICMRRsezcmz0F2ztEhd7ZjZusrUFnIB2CQ+hjjSZz3fIPsu8QXYJtf/AXiLQ2UAZDaicmF6aazcbAW/avkU1Sov4/uXaIrHXyqm3wfLhqNHfxa4WjYyygM20zDhY0rvlnAXY3//kwWM= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=redhat.com; spf=pass smtp.mailfrom=redhat.com; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b=ZbwFqlEW; arc=none smtp.client-ip=170.10.129.124 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=redhat.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=redhat.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="ZbwFqlEW" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1748384630; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=xbqhgC3A/TbOraVkQUQ0RN7Suk368O2IC9TDHM6wKkg=; b=ZbwFqlEWDmpMUm7xZxKgv14sPCxfsZjB8nBgOtSUfhdfcsSveckpgET4sFldy8eN6BN4lS XyPKcdMqFrBwjmHHVvh+4+aviTDep+5A6tscPqomWPjAcCNt0ViMcDpNH/EyRqXiQJtHDr fj0PbyVraX/MpI410N7vyO2Tmm/l580= Received: from mx-prod-mc-06.mail-002.prod.us-west-2.aws.redhat.com (ec2-35-165-154-97.us-west-2.compute.amazonaws.com [35.165.154.97]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-55-EK0MF0dQPgGJFB6nue86OQ-1; Tue, 27 May 2025 18:23:45 -0400 X-MC-Unique: EK0MF0dQPgGJFB6nue86OQ-1 X-Mimecast-MFC-AGG-ID: EK0MF0dQPgGJFB6nue86OQ_1748384623 Received: from mx-prod-int-02.mail-002.prod.us-west-2.aws.redhat.com (mx-prod-int-02.mail-002.prod.us-west-2.aws.redhat.com [10.30.177.15]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by mx-prod-mc-06.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id 90B6C1800258; Tue, 27 May 2025 22:23:43 +0000 (UTC) Received: from chopper.redhat.com (unknown [10.22.88.105]) by mx-prod-int-02.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTP id 82F741956095; Tue, 27 May 2025 22:23:39 +0000 (UTC) From: Lyude Paul To: rust-for-linux@vger.kernel.org, Thomas Gleixner , Boqun Feng , linux-kernel@vger.kernel.org, Daniel Almeida Cc: Miguel Ojeda , Alex Gaynor , Gary Guo , =?UTF-8?q?Bj=C3=B6rn=20Roy=20Baron?= , Benno Lossin , Andreas Hindborg , Alice Ryhl , Trevor Gross , Danilo Krummrich , Peter Zijlstra , Ingo Molnar , Will Deacon , Waiman Long , Mitchell Levy , Wedson Almeida Filho Subject: [RFC RESEND v10 06/14] rust: sync: Add SpinLockIrq Date: Tue, 27 May 2025 18:21:47 -0400 Message-ID: <20250527222254.565881-7-lyude@redhat.com> In-Reply-To: <20250527222254.565881-1-lyude@redhat.com> References: <20250527222254.565881-1-lyude@redhat.com> Precedence: bulk X-Mailing-List: rust-for-linux@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Scanned-By: MIMEDefang 3.0 on 10.30.177.15 A variant of SpinLock that is expected to be used in noirq contexts, so lock() will disable interrupts and unlock() (i.e. `Guard::drop()` will undo the interrupt disable. [Boqun: Port to use spin_lock_irq_disable() and spin_unlock_irq_enable()] Signed-off-by: Lyude Paul Co-Developed-by: Boqun Feng Signed-off-by: Boqun Feng --- V10: * Also add support to GlobalLock * Documentation fixes from Dirk Signed-off-by: Lyude Paul --- rust/kernel/sync.rs | 4 +- rust/kernel/sync/lock/global.rs | 3 + rust/kernel/sync/lock/spinlock.rs | 142 ++++++++++++++++++++++++++++++ 3 files changed, 148 insertions(+), 1 deletion(-) diff --git a/rust/kernel/sync.rs b/rust/kernel/sync.rs index 36a7190155833..07e83992490d5 100644 --- a/rust/kernel/sync.rs +++ b/rust/kernel/sync.rs @@ -20,7 +20,9 @@ pub use condvar::{new_condvar, CondVar, CondVarTimeoutResult}; pub use lock::global::{global_lock, GlobalGuard, GlobalLock, GlobalLockBackend, GlobalLockedBy}; pub use lock::mutex::{new_mutex, Mutex, MutexGuard}; -pub use lock::spinlock::{new_spinlock, SpinLock, SpinLockGuard}; +pub use lock::spinlock::{ + new_spinlock, new_spinlock_irq, SpinLock, SpinLockGuard, SpinLockIrq, SpinLockIrqGuard, +}; pub use locked_by::LockedBy; /// Represents a lockdep class. It's a wrapper around C's `lock_class_key`. diff --git a/rust/kernel/sync/lock/global.rs b/rust/kernel/sync/lock/global.rs index d65f94b5caf26..47e200b750c1d 100644 --- a/rust/kernel/sync/lock/global.rs +++ b/rust/kernel/sync/lock/global.rs @@ -299,4 +299,7 @@ macro_rules! global_lock_inner { (backend SpinLock) => { $crate::sync::lock::spinlock::SpinLockBackend }; + (backend SpinLockIrq) => { + $crate::sync::lock::spinlock::SpinLockIrqBackend + }; } diff --git a/rust/kernel/sync/lock/spinlock.rs b/rust/kernel/sync/lock/spinlock.rs index d7be38ccbdc7d..a1d76184a5bb4 100644 --- a/rust/kernel/sync/lock/spinlock.rs +++ b/rust/kernel/sync/lock/spinlock.rs @@ -139,3 +139,145 @@ unsafe fn assert_is_held(ptr: *mut Self::State) { unsafe { bindings::spin_assert_is_held(ptr) } } } + +/// Creates a [`SpinLockIrq`] initialiser with the given name and a newly-created lock class. +/// +/// It uses the name if one is given, otherwise it generates one based on the file name and line +/// number. +#[macro_export] +macro_rules! new_spinlock_irq { + ($inner:expr $(, $name:literal)? $(,)?) => { + $crate::sync::SpinLockIrq::new( + $inner, $crate::optional_name!($($name)?), $crate::static_lock_class!()) + }; +} +pub use new_spinlock_irq; + +/// A spinlock that may be acquired when local processor interrupts are disabled. +/// +/// This is a version of [`SpinLock`] that can only be used in contexts where interrupts for the +/// local CPU are disabled. It can be acquired in two ways: +/// +/// - Using [`lock()`] like any other type of lock, in which case the bindings will modify the +/// interrupt state to ensure that local processor interrupts remain disabled for at least as long +/// as the [`SpinLockIrqGuard`] exists. +/// - Using [`lock_with()`] in contexts where a [`LocalInterruptDisabled`] token is present and +/// local processor interrupts are already known to be disabled, in which case the local interrupt +/// state will not be touched. This method should be preferred if a [`LocalInterruptDisabled`] +/// token is present in the scope. +/// +/// For more info on spinlocks, see [`SpinLock`]. For more information on interrupts, +/// [see the interrupt module](kernel::interrupt). +/// +/// # Examples +/// +/// The following example shows how to declare, allocate initialise and access a struct (`Example`) +/// that contains an inner struct (`Inner`) that is protected by a spinlock that requires local +/// processor interrupts to be disabled. +/// +/// ``` +/// use kernel::sync::{new_spinlock_irq, SpinLockIrq}; +/// +/// struct Inner { +/// a: u32, +/// b: u32, +/// } +/// +/// #[pin_data] +/// struct Example { +/// #[pin] +/// c: SpinLockIrq, +/// #[pin] +/// d: SpinLockIrq, +/// } +/// +/// impl Example { +/// fn new() -> impl PinInit { +/// pin_init!(Self { +/// c <- new_spinlock_irq!(Inner { a: 0, b: 10 }), +/// d <- new_spinlock_irq!(Inner { a: 20, b: 30 }), +/// }) +/// } +/// } +/// +/// // Allocate a boxed `Example` +/// let e = KBox::pin_init(Example::new(), GFP_KERNEL)?; +/// +/// // Accessing an `Example` from a context where interrupts may not be disabled already. +/// let c_guard = e.c.lock(); // interrupts are disabled now, +1 interrupt disable refcount +/// let d_guard = e.d.lock(); // no interrupt state change, +1 interrupt disable refcount +/// +/// assert_eq!(c_guard.a, 0); +/// assert_eq!(c_guard.b, 10); +/// assert_eq!(d_guard.a, 20); +/// assert_eq!(d_guard.b, 30); +/// +/// drop(c_guard); // Dropping c_guard will not re-enable interrupts just yet, since d_guard is +/// // still in scope. +/// drop(d_guard); // Last interrupt disable reference dropped here, so interrupts are re-enabled +/// // now +/// # Ok::<(), Error>(()) +/// ``` +/// +/// [`lock()`]: SpinLockIrq::lock +/// [`lock_with()`]: SpinLockIrq::lock_with +pub type SpinLockIrq = super::Lock; + +/// A kernel `spinlock_t` lock backend that is acquired in interrupt disabled contexts. +pub struct SpinLockIrqBackend; + +/// A [`Guard`] acquired from locking a [`SpinLockIrq`] using [`lock()`]. +/// +/// This is simply a type alias for a [`Guard`] returned from locking a [`SpinLockIrq`] using +/// [`lock_with()`]. It will unlock the [`SpinLockIrq`] and decrement the local processor's +/// interrupt disablement refcount upon being dropped. +/// +/// [`Guard`]: super::Guard +/// [`lock()`]: SpinLockIrq::lock +/// [`lock_with()`]: SpinLockIrq::lock_with +pub type SpinLockIrqGuard<'a, T> = super::Guard<'a, T, SpinLockIrqBackend>; + +// SAFETY: The underlying kernel `spinlock_t` object ensures mutual exclusion. `relock` uses the +// default implementation that always calls the same locking method. +unsafe impl super::Backend for SpinLockIrqBackend { + type State = bindings::spinlock_t; + type GuardState = (); + + unsafe fn init( + ptr: *mut Self::State, + name: *const crate::ffi::c_char, + key: *mut bindings::lock_class_key, + ) { + // SAFETY: The safety requirements ensure that `ptr` is valid for writes, and `name` and + // `key` are valid for read indefinitely. + unsafe { bindings::__spin_lock_init(ptr, name, key) } + } + + unsafe fn lock(ptr: *mut Self::State) -> Self::GuardState { + // SAFETY: The safety requirements of this function ensure that `ptr` points to valid + // memory, and that it has been initialised before. + unsafe { bindings::spin_lock_irq_disable(ptr) } + } + + unsafe fn unlock(ptr: *mut Self::State, _guard_state: &Self::GuardState) { + // SAFETY: The safety requirements of this function ensure that `ptr` is valid and that the + // caller is the owner of the spinlock. + unsafe { bindings::spin_unlock_irq_enable(ptr) } + } + + unsafe fn try_lock(ptr: *mut Self::State) -> Option { + // SAFETY: The `ptr` pointer is guaranteed to be valid and initialized before use. + let result = unsafe { bindings::spin_trylock_irq_disable(ptr) }; + + if result != 0 { + Some(()) + } else { + None + } + } + + unsafe fn assert_is_held(ptr: *mut Self::State) { + // SAFETY: The `ptr` pointer is guaranteed to be valid and initialized before use. + unsafe { bindings::spin_assert_is_held(ptr) } + } +} -- 2.49.0