From nobody Mon Oct 6 20:57:09 2025 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 27F8C20C469 for ; Thu, 17 Jul 2025 18:42:04 +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=1752777727; cv=none; b=REoQc5aXR3mGUDe5e0R2xEdC7fk5872dbHPMfTNMg4d2SIi6eqMeCWOKwA0steW89bEagk9q2ZuGV76V5dmz3cDqYEjHZuxl3h5h6JiMeB4iqUAcs+hnR4hU7N/UdAthB5EseE/BwFhWxGgMScaoe34neg4a+lrjstk8j7aYFLw= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1752777727; c=relaxed/simple; bh=fv0foUTsis6Haf+PhpmFVXu8yZ8qV/XNhXODYBZziI4=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=cVP+YRaKbZxHyqZMxXhZ6pb0RwjREewdQUYaFkvt+8+JNbhj44e2VC5Qjlab5X6E1I49G8/Em2jZyoYccBqGIhGm0gfOoAmvbGfbcWXku9yZswHitcMa46FL82IRAVM6biXbWbteDgcozk9hBJDe034nYh/qklhqaSP2la5uRUQ= 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=diBZUyNM; 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="diBZUyNM" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1752777724; 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=c/WNrderCmnKbVmqzWaYelh1TPZXBh/rP4QETzIcIrA=; b=diBZUyNMRG5v89xYjZtJSkC1IrhoCqGDPCRQjtIxd6dqgU4ogSsY5ON1lOfwfkN7+6qhX/ VzAw5d5zgVh4NidNzEw0t4rPSM2YoASP/kkv1b1EAJY1poRtzDGYxsOUp7MakFH612HLdF VotmT+Tyup5jFNTqY9Vk5RWR2+o5XtA= Received: from mx-prod-mc-05.mail-002.prod.us-west-2.aws.redhat.com (ec2-54-186-198-63.us-west-2.compute.amazonaws.com [54.186.198.63]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-669-tkcOYB9TNKCXErq5dvtl6A-1; Thu, 17 Jul 2025 14:41:57 -0400 X-MC-Unique: tkcOYB9TNKCXErq5dvtl6A-1 X-Mimecast-MFC-AGG-ID: tkcOYB9TNKCXErq5dvtl6A_1752777713 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-05.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id 911841955F3C; Thu, 17 Jul 2025 18:41:53 +0000 (UTC) Received: from chopper.redhat.com (unknown [10.22.66.69]) by mx-prod-int-05.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTP id 0EF2A195608D; Thu, 17 Jul 2025 18:41:49 +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 , Viresh Kumar Subject: [PATCH v11 07/14] rust: sync: Add SpinLockIrq Date: Thu, 17 Jul 2025 14:37:59 -0400 Message-ID: <20250717184055.2071216-8-lyude@redhat.com> In-Reply-To: <20250717184055.2071216-1-lyude@redhat.com> References: <20250717184055.2071216-1-lyude@redhat.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable X-Scanned-By: MIMEDefang 3.0 on 10.30.177.17 Content-Type: text/plain; charset="utf-8" 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 V11: * Add unit test requested by Daniel Almeida --- rust/kernel/sync.rs | 4 +- rust/kernel/sync/lock/global.rs | 3 + rust/kernel/sync/lock/spinlock.rs | 229 ++++++++++++++++++++++++++++++ 3 files changed, 235 insertions(+), 1 deletion(-) diff --git a/rust/kernel/sync.rs b/rust/kernel/sync.rs index 63c99e015ad6f..f1e448e096ea9 100644 --- a/rust/kernel/sync.rs +++ b/rust/kernel/sync.rs @@ -22,7 +22,9 @@ pub use condvar::{new_condvar, CondVar, CondVarTimeoutResult}; pub use lock::global::{global_lock, GlobalGuard, GlobalLock, GlobalLockBac= kend, 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; =20 /// 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) =3D> { $crate::sync::lock::spinlock::SpinLockBackend }; + (backend SpinLockIrq) =3D> { + $crate::sync::lock::spinlock::SpinLockIrqBackend + }; } diff --git a/rust/kernel/sync/lock/spinlock.rs b/rust/kernel/sync/lock/spin= lock.rs index d7be38ccbdc7d..6e6d571acd90c 100644 --- a/rust/kernel/sync/lock/spinlock.rs +++ b/rust/kernel/sync/lock/spinlock.rs @@ -3,6 +3,7 @@ //! A kernel spinlock. //! //! This module allows Rust code to use the kernel's `spinlock_t`. +use crate::prelude::*; =20 /// Creates a [`SpinLock`] initialiser with the given name and a newly-cre= ated lock class. /// @@ -139,3 +140,231 @@ unsafe fn assert_is_held(ptr: *mut Self::State) { unsafe { bindings::spin_assert_is_held(ptr) } } } + +/// Creates a [`SpinLockIrq`] initialiser with the given name and a newly-= created lock class. +/// +/// It uses the name if one is given, otherwise it generates one based on = the file name and line +/// number. +#[macro_export] +macro_rules! new_spinlock_irq { + ($inner:expr $(, $name:literal)? $(,)?) =3D> { + $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 di= sabled. +/// +/// This is a version of [`SpinLock`] that can only be used in contexts wh= ere 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 bind= ings will modify the +/// interrupt state to ensure that local processor interrupts remain dis= abled 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 whic= h case the local interrupt +/// state will not be touched. This method should be preferred if a [`Lo= calInterruptDisabled`] +/// 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 ac= cess a struct (`Example`) +/// that contains an inner struct (`Inner`) that is protected by a spinloc= k 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 =3D KBox::pin_init(Example::new(), GFP_KERNEL)?; +/// +/// // Accessing an `Example` from a context where interrupts may not be d= isabled already. +/// let c_guard =3D e.c.lock(); // interrupts are disabled now, +1 interru= pt disable refcount +/// let d_guard =3D 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 in= terrupts are re-enabled +/// // now +/// # Ok::<(), Error>(()) +/// ``` +/// +/// [`lock()`]: SpinLockIrq::lock +/// [`lock_with()`]: SpinLockIrq::lock_with +pub type SpinLockIrq =3D super::Lock; + +/// A kernel `spinlock_t` lock backend that is acquired in interrupt disab= led 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> =3D super::Guard<'a, T, SpinLockIrqBacken= d>; + +// SAFETY: The underlying kernel `spinlock_t` object ensures mutual exclus= ion. `relock` uses the +// default implementation that always calls the same locking method. +unsafe impl super::Backend for SpinLockIrqBackend { + type State =3D bindings::spinlock_t; + type GuardState =3D (); + + 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 `p= tr` 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::GuardStat= e) { + // SAFETY: The safety requirements of this function ensure that `p= tr` 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 initial= ized before use. + let result =3D unsafe { bindings::spin_trylock_irq_disable(ptr) }; + + if result !=3D 0 { + Some(()) + } else { + None + } + } + + unsafe fn assert_is_held(ptr: *mut Self::State) { + // SAFETY: The `ptr` pointer is guaranteed to be valid and initial= ized before use. + unsafe { bindings::spin_assert_is_held(ptr) } + } +} + +#[kunit_tests(rust_spinlock_irq_condvar)] +mod tests { + use super::*; + use crate::{ + sync::*, + workqueue::{self, impl_has_work, new_work, Work, WorkItem}, + }; + + struct TestState { + value: u32, + waiter_ready: bool, + } + + #[pin_data] + struct Test { + #[pin] + state: SpinLockIrq, + + #[pin] + state_changed: CondVar, + + #[pin] + waiter_state_changed: CondVar, + + #[pin] + wait_work: Work, + } + + impl_has_work! { + impl HasWork for Test { self.wait_work } + } + + impl Test { + pub(crate) fn new() -> Result> { + Arc::try_pin_init( + try_pin_init!( + Self { + state <- new_spinlock_irq!(TestState { + value: 1, + waiter_ready: false + }), + state_changed <- new_condvar!(), + waiter_state_changed <- new_condvar!(), + wait_work <- new_work!("IrqCondvarTest::wait_work") + } + ), + GFP_KERNEL, + ) + } + } + + impl WorkItem for Test { + type Pointer =3D Arc; + + fn run(this: Arc) { + // Wait for the test to be ready to wait for us + let mut state =3D this.state.lock(); + + while !state.waiter_ready { + this.waiter_state_changed.wait(&mut state); + } + + // Deliver the exciting value update our test has been waiting= for + state.value +=3D 1; + this.state_changed.notify_sync(); + } + } + + #[test] + fn spinlock_irq_condvar() -> Result { + let testdata =3D Test::new()?; + + let _ =3D workqueue::system().enqueue(testdata.clone()); + + // Let the updater know when we're ready to wait + let mut state =3D testdata.state.lock(); + state.waiter_ready =3D true; + testdata.waiter_state_changed.notify_sync(); + + // Wait for the exciting value update + testdata.state_changed.wait(&mut state); + assert_eq!(state.value, 2); + Ok(()) + } +} --=20 2.50.0