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 D614B27293B for ; Thu, 27 Feb 2025 22:21:57 +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=1740694919; cv=none; b=cfKx3mtPD76gjIYPpqAz3gPlNBf6h8JcHXXXmM5WG/hwk55vd6bhHYHOJjmFl2+sUIYULVIXSLC4lCYtSfVX8wu7F6KmoHPbyWcAP8SntRDxoDGmtrkdONK0Iu4TW0q+wCZBBnGkG4Hksv4kZzOZCfz5X1BOM7EOdI4zGJ+3bP4= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1740694919; c=relaxed/simple; bh=ND5S6wGMSfNT1qvWcfAMGpPAEVYEokGaSp2aWt3EvdQ=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=Ux3RQaN/coNE6+ncTeThEiEVDWliVG+YvBps6sjtn/r/tm6vmGiOq5aRLz0pXWFKqE0hBOjnc6hv5qbwYruSdDdfNCQiuTs03pBkLk1NwpgNaWuujdTUQa6lVz0tHnwiYtJEmGKXcnHrJ/nAbfl6SiIiKqVIG3hqfB694qi/zIc= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none 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=CW99M7Rt; arc=none smtp.client-ip=170.10.129.124 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none 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="CW99M7Rt" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1740694917; 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=4sQthDH4qQkV46b2m1wjGzV8BsA/0Fq5VvPcWCxI/HA=; b=CW99M7RtpmTlfA41Wsef6MZma5RHAbQf0CKkqbx6/3zitqTYzUkLF96g/kOegHVm7p+Vdb WKHi3XF2r9B9YNSM7BBqJ3VfIHNwXxuCc/6K7uVuMR/nzX1dOO/3EEj9t4Em8kYiHVJ2Mw SzQ5K0XLzpRI7EypXih7NKJQ3/P4OAE= Received: from mx-prod-mc-08.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-621-1uwPcSWRPVq8jlavufDNHg-1; Thu, 27 Feb 2025 17:21:55 -0500 X-MC-Unique: 1uwPcSWRPVq8jlavufDNHg-1 X-Mimecast-MFC-AGG-ID: 1uwPcSWRPVq8jlavufDNHg_1740694908 Received: from mx-prod-int-05.mail-002.prod.us-west-2.aws.redhat.com (mx-prod-int-05.mail-002.prod.us-west-2.aws.redhat.com [10.30.177.17]) (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-08.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id 652171801A1F; Thu, 27 Feb 2025 22:21:48 +0000 (UTC) Received: from chopper.lyude.net (unknown [10.22.89.128]) by mx-prod-int-05.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTP id DD28F1944D02; Thu, 27 Feb 2025 22:21:44 +0000 (UTC) From: Lyude Paul To: rust-for-linux@vger.kernel.org, Thomas Gleixner Cc: Boqun Feng , Miguel Ojeda , Alex Gaynor , Gary Guo , =?UTF-8?q?Bj=C3=B6rn=20Roy=20Baron?= , Benno Lossin , Andreas Hindborg , Alice Ryhl , Trevor Gross , Peter Zijlstra , Ingo Molnar , Will Deacon , Waiman Long , Wedson Almeida Filho , linux-kernel@vger.kernel.org (open list) Subject: [PATCH v9 6/9] rust: sync: Add SpinLockIrq Date: Thu, 27 Feb 2025 17:10:17 -0500 Message-ID: <20250227221924.265259-7-lyude@redhat.com> In-Reply-To: <20250227221924.265259-1-lyude@redhat.com> References: <20250227221924.265259-1-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 10.30.177.17 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 --- rust/kernel/sync.rs | 4 +- rust/kernel/sync/lock/spinlock.rs | 141 ++++++++++++++++++++++++++++++ 2 files changed, 144 insertions(+), 1 deletion(-) diff --git a/rust/kernel/sync.rs b/rust/kernel/sync.rs index 3498fb344dc93..fcd2ea5f7f287 100644 --- a/rust/kernel/sync.rs +++ b/rust/kernel/sync.rs @@ -18,7 +18,9 @@ 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/spinlock.rs b/rust/kernel/sync/lock/spinlock.rs index ab2f8d0753116..ac66493f681ce 100644 --- a/rust/kernel/sync/lock/spinlock.rs +++ b/rust/kernel/sync/lock/spinlock.rs @@ -139,3 +139,144 @@ 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 ensure that +/// 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) } + } +} -- 2.48.1