projects/linux·blob v6.18 · refs

124 lines · 4.1 KiB

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;
23
24pub use arc::{Arc, ArcBorrow, UniqueArc};
25pub use completion::Completion;
26pub use condvar::{new_condvar, CondVar, CondVarTimeoutResult};
27pub use lock::global::{global_lock, GlobalGuard, GlobalLock, GlobalLockBackend, GlobalLockedBy};
28pub use lock::mutex::{new_mutex, Mutex, MutexGuard};
29pub use lock::spinlock::{new_spinlock, SpinLock, SpinLockGuard};
30pub use locked_by::LockedBy;
31pub use refcount::Refcount;
32
33/// Represents a lockdep class. It's a wrapper around C's `lock_class_key`.
34#[repr(transparent)]
35#[pin_data(PinnedDrop)]
36pub struct LockClassKey {
37 #[pin]
38 inner: Opaque<bindings::lock_class_key>,
39}
40
41// SAFETY: `bindings::lock_class_key` is designed to be used concurrently from multiple threads and
42// provides its own synchronization.
43unsafe impl Sync for LockClassKey {}
44
45impl LockClassKey {
46 /// Initializes a dynamically allocated lock class key. In the common case of using a
47 /// statically allocated lock class key, the static_lock_class! macro should be used instead.
48 ///
49 /// # Examples
50 /// ```
51 /// # use kernel::c_str;
52 /// # use kernel::alloc::KBox;
53 /// # use kernel::types::ForeignOwnable;
54 /// # use kernel::sync::{LockClassKey, SpinLock};
55 /// # use pin_init::stack_pin_init;
56 ///
57 /// let key = KBox::pin_init(LockClassKey::new_dynamic(), GFP_KERNEL)?;
58 /// let key_ptr = key.into_foreign();
59 ///
60 /// {
61 /// stack_pin_init!(let num: SpinLock<u32> = SpinLock::new(
62 /// 0,
63 /// c_str!("my_spinlock"),
64 /// // SAFETY: `key_ptr` is returned by the above `into_foreign()`, whose
65 /// // `from_foreign()` has not yet been called.
66 /// unsafe { <Pin<KBox<LockClassKey>> as ForeignOwnable>::borrow(key_ptr) }
67 /// ));
68 /// }
69 ///
70 /// // SAFETY: We dropped `num`, the only use of the key, so the result of the previous
71 /// // `borrow` has also been dropped. Thus, it's safe to use from_foreign.
72 /// unsafe { drop(<Pin<KBox<LockClassKey>> as ForeignOwnable>::from_foreign(key_ptr)) };
73 ///
74 /// # Ok::<(), Error>(())
75 /// ```
76 pub fn new_dynamic() -> impl PinInit<Self> {
77 pin_init!(Self {
78 // SAFETY: lockdep_register_key expects an uninitialized block of memory
79 inner <- Opaque::ffi_init(|slot| unsafe { bindings::lockdep_register_key(slot) })
80 })
81 }
82
83 pub(crate) fn as_ptr(&self) -> *mut bindings::lock_class_key {
84 self.inner.get()
85 }
86}
87
88#[pinned_drop]
89impl PinnedDrop for LockClassKey {
90 fn drop(self: Pin<&mut Self>) {
91 // SAFETY: self.as_ptr was registered with lockdep and self is pinned, so the address
92 // hasn't changed. Thus, it's safe to pass to unregister.
93 unsafe { bindings::lockdep_unregister_key(self.as_ptr()) }
94 }
95}
96
97/// Defines a new static lock class and returns a pointer to it.
98#[doc(hidden)]
99#[macro_export]
100macro_rules! static_lock_class {
101 () => {{
102 static CLASS: $crate::sync::LockClassKey =
103 // Lockdep expects uninitialized memory when it's handed a statically allocated `struct
104 // lock_class_key`.
105 //
106 // SAFETY: `LockClassKey` transparently wraps `Opaque` which permits uninitialized
107 // memory.
108 unsafe { ::core::mem::MaybeUninit::uninit().assume_init() };
109 $crate::prelude::Pin::static_ref(&CLASS)
110 }};
111}
112
113/// Returns the given string, if one is provided, otherwise generates one based on the source code
114/// location.
115#[doc(hidden)]
116#[macro_export]
117macro_rules! optional_name {
118 () => {
119 $crate::c_str!(::core::concat!(::core::file!(), ":", ::core::line!()))
120 };
121 ($name:literal) => {
122 $crate::c_str!($name)
123 };
124}