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[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 V14: * Improve rustdoc for SpinLockIrqBackend V17: * Update Git summary according to Benno's review 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 5df87e2bd212e..48a7cae86c50c 100644 --- a/rust/kernel/sync.rs +++ b/rust/kernel/sync.rs @@ -27,7 +27,9 @@ 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; pub use refcount::Refcount; pub use set_once::SetOnce; diff --git a/rust/kernel/sync/lock/global.rs b/rust/kernel/sync/lock/global.rs index eab48108a4aeb..7030a47bc0ad1 100644 --- a/rust/kernel/sync/lock/global.rs +++ b/rust/kernel/sync/lock/global.rs @@ -302,4 +302,7 @@ macro_rules! global_lock_inner { (backend SpinLock) => { $crate::sync::lock::spinlock::SpinLockBackend }; + (backend SpinLockIrq) => { + $crate::sync::lock::spinlock::SpinLockIrqBackend + }; } diff --git a/rust/kernel/sync/lock/spinlock.rs b/rust/kernel/sync/lock/spinlock.rs index d7be38ccbdc7d..3fdfb0a8a0ab1 100644 --- a/rust/kernel/sync/lock/spinlock.rs +++ b/rust/kernel/sync/lock/spinlock.rs @@ -3,6 +3,7 @@ //! A kernel spinlock. //! //! This module allows Rust code to use the kernel's `spinlock_t`. +use crate::prelude::*; /// Creates a [`SpinLock`] initialiser with the given name and a newly-created lock class. /// @@ -139,3 +140,231 @@ unsafe fn assert_is_held(ptr: *mut Self::State) { unsafe { bindings::spin_assert_is_held(ptr) } } } + +/// Creates a [`SpinLockIrq`] initialiser with the given name and a newly-created lock class. +/// +/// It uses the name if one is given, otherwise it generates one based on the file name and line +/// number. +#[macro_export] +macro_rules! new_spinlock_irq { + ($inner:expr $(, $name:literal)? $(,)?) => { + $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 can only be 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) } + } +} + +#[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 = Arc; + + fn run(this: Arc) { + // Wait for the test to be ready to wait for us + let mut state = 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 += 1; + this.state_changed.notify_sync(); + } + } + + #[test] + fn spinlock_irq_condvar() -> Result { + let testdata = Test::new()?; + + let _ = workqueue::system().enqueue(testdata.clone()); + + // Let the updater know when we're ready to wait + let mut state = testdata.state.lock(); + state.waiter_ready = 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(()) + } +} -- 2.52.0