kernel/
sync.rs

1// SPDX-License-Identifier: GPL-2.0
2
3//! Synchronisation primitives.
4//!
5//! This module contains the kernel APIs related to synchronisation that have been ported or
6//! wrapped for usage by Rust code in the kernel.
7
8use crate::prelude::*;
9use crate::types::Opaque;
10use pin_init;
11
12mod arc;
13pub mod aref;
14pub mod atomic;
15pub mod barrier;
16pub mod completion;
17mod condvar;
18pub mod lock;
19mod locked_by;
20pub mod poll;
21pub mod rcu;
22mod refcount;
23mod set_once;
24pub mod srcu;
25
26pub use arc::{Arc, ArcBorrow, UniqueArc};
27pub use completion::Completion;
28pub use condvar::{new_condvar, CondVar, CondVarTimeoutResult};
29pub use lock::global::{global_lock, GlobalGuard, GlobalLock, GlobalLockBackend, GlobalLockedBy};
30pub use lock::mutex::{new_mutex, Mutex, MutexGuard};
31pub use lock::spinlock::{
32    new_spinlock,
33    new_spinlock_irq,
34    SpinLock,
35    SpinLockGuard,
36    SpinLockIrq,
37    SpinLockIrqGuard, //
38};
39pub use locked_by::LockedBy;
40pub use refcount::Refcount;
41pub use set_once::SetOnce;
42pub use srcu::Srcu;
43
44/// Represents a lockdep class.
45///
46/// Wraps the kernel's `struct lock_class_key`.
47#[repr(transparent)]
48#[pin_data(PinnedDrop)]
49pub struct LockClassKey {
50    #[pin]
51    inner: Opaque<bindings::lock_class_key>,
52}
53
54// SAFETY: Unregistering a lock class key from a different thread than where it was registered is
55// allowed.
56unsafe impl Send for LockClassKey {}
57
58// SAFETY: `bindings::lock_class_key` is designed to be used concurrently from multiple threads and
59// provides its own synchronization.
60unsafe impl Sync for LockClassKey {}
61
62impl LockClassKey {
63    /// Initializes a statically allocated lock class key.
64    ///
65    /// This is usually used indirectly through the [`static_lock_class!`] macro. See its
66    /// documentation for more information.
67    ///
68    /// # Safety
69    ///
70    /// * Before using the returned value, it must be pinned in a static memory location.
71    /// * The destructor must never run on the returned `LockClassKey`.
72    pub const unsafe fn new_static() -> Self {
73        LockClassKey {
74            inner: Opaque::uninit(),
75        }
76    }
77
78    /// Initializes a dynamically allocated lock class key.
79    ///
80    /// In the common case of using a statically allocated lock class key, the
81    /// [`static_lock_class!`] macro should be used instead.
82    ///
83    /// # Examples
84    ///
85    /// ```
86    /// use kernel::alloc::KBox;
87    /// use kernel::types::ForeignOwnable;
88    /// use kernel::sync::{LockClassKey, SpinLock};
89    /// use pin_init::stack_pin_init;
90    ///
91    /// let key = KBox::pin_init(LockClassKey::new_dynamic(), GFP_KERNEL)?;
92    /// let key_ptr = key.into_foreign();
93    ///
94    /// {
95    ///     stack_pin_init!(let num: SpinLock<u32> = SpinLock::new(
96    ///         0,
97    ///         c"my_spinlock",
98    ///         // SAFETY: `key_ptr` is returned by the above `into_foreign()`, whose
99    ///         // `from_foreign()` has not yet been called.
100    ///         unsafe { <Pin<KBox<LockClassKey>> as ForeignOwnable>::borrow(key_ptr) }
101    ///     ));
102    /// }
103    ///
104    /// // SAFETY: We dropped `num`, the only use of the key, so the result of the previous
105    /// // `borrow` has also been dropped. Thus, it's safe to use from_foreign.
106    /// unsafe { drop(<Pin<KBox<LockClassKey>> as ForeignOwnable>::from_foreign(key_ptr)) };
107    /// # Ok::<(), Error>(())
108    /// ```
109    pub fn new_dynamic() -> impl PinInit<Self> {
110        pin_init!(Self {
111            // SAFETY: lockdep_register_key expects an uninitialized block of memory
112            inner <- Opaque::ffi_init(|slot| unsafe { bindings::lockdep_register_key(slot) })
113        })
114    }
115
116    /// Returns a raw pointer to the inner C struct.
117    ///
118    /// It is up to the caller to use the raw pointer correctly.
119    pub fn as_ptr(&self) -> *mut bindings::lock_class_key {
120        self.inner.get()
121    }
122}
123
124#[pinned_drop]
125impl PinnedDrop for LockClassKey {
126    fn drop(self: Pin<&mut Self>) {
127        // SAFETY: `self.as_ptr()` was registered with lockdep and `self` is pinned, so the address
128        // hasn't changed. Thus, it's safe to pass it to unregister.
129        unsafe { bindings::lockdep_unregister_key(self.as_ptr()) }
130    }
131}
132
133/// Defines a new static lock class and returns a pointer to it.
134///
135/// # Examples
136///
137/// ```
138/// use kernel::sync::{static_lock_class, Arc, SpinLock};
139///
140/// fn new_locked_int() -> Result<Arc<SpinLock<u32>>> {
141///     Arc::pin_init(SpinLock::new(
142///         42,
143///         c"new_locked_int",
144///         static_lock_class!(),
145///     ), GFP_KERNEL)
146/// }
147/// ```
148#[macro_export]
149macro_rules! static_lock_class {
150    () => {{
151        static CLASS: $crate::sync::LockClassKey =
152            // SAFETY: The returned `LockClassKey` is stored in static memory and we pin it. Drop
153            // never runs on a static global.
154            unsafe { $crate::sync::LockClassKey::new_static() };
155        $crate::prelude::Pin::static_ref(&CLASS)
156    }};
157}
158pub use static_lock_class;
159
160/// Returns the given string, if one is provided, otherwise generates one based on the source code
161/// location.
162#[doc(hidden)]
163#[macro_export]
164macro_rules! optional_name {
165    () => {
166        $crate::c_str!(::core::concat!(::core::file!(), ":", ::core::line!()))
167    };
168    ($name:literal) => {
169        $crate::c_str!($name)
170    };
171}
kernel/sync.rs

kernel/
sync.rs
