Messages in this thread | | | Date | Sun, 9 Apr 2023 13:48:07 -0300 | From | Martin Rodriguez Reboredo <> | Subject | Re: [PATCH v3 05/13] rust: lock: introduce `SpinLock` |
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On 4/8/23 04:53, Wedson Almeida Filho wrote: > From: Wedson Almeida Filho <walmeida@microsoft.com> > > This is the `spinlock_t` lock backend and allows Rust code to use the > kernel spinlock idiomatically. > > Cc: Peter Zijlstra <peterz@infradead.org> > Cc: Ingo Molnar <mingo@redhat.com> > Cc: Will Deacon <will@kernel.org> > Cc: Waiman Long <longman@redhat.com> > Signed-off-by: Wedson Almeida Filho <walmeida@microsoft.com> > --- > v1 -> v2: No changes > v2 -> v3: No changes > > rust/helpers.c | 24 +++++++ > rust/kernel/sync.rs | 2 +- > rust/kernel/sync/lock.rs | 1 + > rust/kernel/sync/lock/spinlock.rs | 116 ++++++++++++++++++++++++++++++ > 4 files changed, 142 insertions(+), 1 deletion(-) > create mode 100644 rust/kernel/sync/lock/spinlock.rs > > diff --git a/rust/helpers.c b/rust/helpers.c > index 3010a2ec26e2..05694e3f8f70 100644 > --- a/rust/helpers.c > +++ b/rust/helpers.c > @@ -22,6 +22,7 @@ > #include <linux/build_bug.h> > #include <linux/refcount.h> > #include <linux/mutex.h> > +#include <linux/spinlock.h> > > __noreturn void rust_helper_BUG(void) > { > @@ -35,6 +36,29 @@ void rust_helper_mutex_lock(struct mutex *lock) > } > EXPORT_SYMBOL_GPL(rust_helper_mutex_lock); > > +void rust_helper___spin_lock_init(spinlock_t *lock, const char *name, > + struct lock_class_key *key) > +{ > +#ifdef CONFIG_DEBUG_SPINLOCK > + spin_lock_init_with_key(lock, name, key); > +#else > + spin_lock_init(lock); > +#endif > +} > +EXPORT_SYMBOL_GPL(rust_helper___spin_lock_init); > + > +void rust_helper_spin_lock(spinlock_t *lock) > +{ > + spin_lock(lock); > +} > +EXPORT_SYMBOL_GPL(rust_helper_spin_lock); > + > +void rust_helper_spin_unlock(spinlock_t *lock) > +{ > + spin_unlock(lock); > +} > +EXPORT_SYMBOL_GPL(rust_helper_spin_unlock); > + > refcount_t rust_helper_REFCOUNT_INIT(int n) > { > return (refcount_t)REFCOUNT_INIT(n); > diff --git a/rust/kernel/sync.rs b/rust/kernel/sync.rs > index 693f0b7f4e4f..c997ff7e951e 100644 > --- a/rust/kernel/sync.rs > +++ b/rust/kernel/sync.rs > @@ -11,7 +11,7 @@ mod arc; > pub mod lock; > > pub use arc::{Arc, ArcBorrow, UniqueArc}; > -pub use lock::mutex::Mutex; > +pub use lock::{mutex::Mutex, spinlock::SpinLock}; > > /// Represents a lockdep class. It's a wrapper around C's `lock_class_key`. > #[repr(transparent)] > diff --git a/rust/kernel/sync/lock.rs b/rust/kernel/sync/lock.rs > index 86669f771ee0..df43dff5af5c 100644 > --- a/rust/kernel/sync/lock.rs > +++ b/rust/kernel/sync/lock.rs > @@ -11,6 +11,7 @@ use core::{cell::UnsafeCell, marker::PhantomData, marker::PhantomPinned}; > use macros::pin_data; > > pub mod mutex; > +pub mod spinlock; > > /// The "backend" of a lock. > /// > diff --git a/rust/kernel/sync/lock/spinlock.rs b/rust/kernel/sync/lock/spinlock.rs > new file mode 100644 > index 000000000000..a52d20fc9755 > --- /dev/null > +++ b/rust/kernel/sync/lock/spinlock.rs > @@ -0,0 +1,116 @@ > +// SPDX-License-Identifier: GPL-2.0 > + > +//! A kernel spinlock. > +//! > +//! This module allows Rust code to use the kernel's `spinlock_t`. > + > +use crate::bindings; > + > +/// Creates a [`SpinLock`] 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 { > + ($inner:expr $(, $name:literal)? $(,)?) => { > + $crate::sync::SpinLock::new( > + $inner, $crate::optional_name!($($name)?), $crate::static_lock_class!()) > + }; > +} > + > +/// A spinlock. > +/// > +/// Exposes the kernel's [`spinlock_t`]. When multiple CPUs attempt to lock the same spinlock, only > +/// one at a time is allowed to progress, the others will block (spinning) until the spinlock is > +/// unlocked, at which point another CPU will be allowed to make progress. > +/// > +/// Instances of [`SpinLock`] need a lock class and to be pinned. The recommended way to create such > +/// instances is with the [`pin_init`](crate::pin_init) and [`new_spinlock`] macros. > +/// > +/// # Examples > +/// > +/// The following example shows how to declare, allocate and initialise a struct (`Example`) that > +/// contains an inner struct (`Inner`) that is protected by a spinlock. > +/// > +/// ``` > +/// use kernel::{init::InPlaceInit, init::PinInit, new_spinlock, pin_init, sync::SpinLock}; > +/// > +/// struct Inner { > +/// a: u32, > +/// b: u32, > +/// } > +/// > +/// #[pin_data] > +/// struct Example { > +/// c: u32, > +/// #[pin] > +/// d: SpinLock<Inner>, > +/// } > +/// > +/// impl Example { > +/// fn new() -> impl PinInit<Self> { > +/// pin_init!(Self { > +/// c: 10, > +/// d <- new_spinlock!(Inner { a: 20, b: 30 }), > +/// }) > +/// } > +/// } > +/// > +/// // Allocate a boxed `Example`. > +/// let e = Box::pin_init(Example::new())?; > +/// assert_eq!(e.c, 10); > +/// assert_eq!(e.d.lock().a, 20); > +/// assert_eq!(e.d.lock().b, 30); > +/// ``` > +/// > +/// The following example shows how to use interior mutability to modify the contents of a struct > +/// protected by a spinlock despite only having a shared reference: > +/// > +/// ``` > +/// use kernel::sync::SpinLock; > +/// > +/// struct Example { > +/// a: u32, > +/// b: u32, > +/// } > +/// > +/// fn example(m: &SpinLock<Example>) { > +/// let mut guard = m.lock(); > +/// guard.a += 10; > +/// guard.b += 20; > +/// } > +/// ``` > +/// > +/// [`spinlock_t`]: ../../../../include/linux/spinlock.h > +pub type SpinLock<T> = super::Lock<T, SpinLockBackend>; > + > +/// A kernel `spinlock_t` lock backend. > +pub struct SpinLockBackend; > + > +// SAFETY: The underlying kernel `spinlock_t` object ensures mutual exclusion. > +unsafe impl super::Backend for SpinLockBackend { > + type State = bindings::spinlock_t; > + type GuardState = (); > + > + unsafe fn init( > + ptr: *mut Self::State, > + name: *const core::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(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 mutex. > + unsafe { bindings::spin_unlock(ptr) } > + } > +}
Reviewed-by: Martin Rodriguez Reboredo <yakoyoku@gmail.com>
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