projects/linux·blob v7.1 · refs

162 lines · 5.0 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;
23mod set_once;
24
25pub use arc::{Arc, ArcBorrow, UniqueArc};
26pub use completion::Completion;
27pub use condvar::{new_condvar, CondVar, CondVarTimeoutResult};
28pub use lock::global::{global_lock, GlobalGuard, GlobalLock, GlobalLockBackend, GlobalLockedBy};
29pub use lock::mutex::{new_mutex, Mutex, MutexGuard};
30pub use lock::spinlock::{new_spinlock, SpinLock, SpinLockGuard};
31pub use locked_by::LockedBy;
32pub use refcount::Refcount;
33pub use set_once::SetOnce;
34
35/// Represents a lockdep class.
36///
37/// Wraps the kernel's `struct lock_class_key`.
38#[repr(transparent)]
39#[pin_data(PinnedDrop)]
40pub struct LockClassKey {
41 #[pin]
42 inner: Opaque<bindings::lock_class_key>,
43}
44
45// SAFETY: Unregistering a lock class key from a different thread than where it was registered is
46// allowed.
47unsafe impl Send for LockClassKey {}
48
49// SAFETY: `bindings::lock_class_key` is designed to be used concurrently from multiple threads and
50// provides its own synchronization.
51unsafe impl Sync for LockClassKey {}
52
53impl LockClassKey {
54 /// Initializes a statically allocated lock class key.
55 ///
56 /// This is usually used indirectly through the [`static_lock_class!`] macro. See its
57 /// documentation for more information.
58 ///
59 /// # Safety
60 ///
61 /// * Before using the returned value, it must be pinned in a static memory location.
62 /// * The destructor must never run on the returned `LockClassKey`.
63 pub const unsafe fn new_static() -> Self {
64 LockClassKey {
65 inner: Opaque::uninit(),
66 }
67 }
68
69 /// Initializes a dynamically allocated lock class key.
70 ///
71 /// In the common case of using a statically allocated lock class key, the
72 /// [`static_lock_class!`] macro should be used instead.
73 ///
74 /// # Examples
75 ///
76 /// ```
77 /// use kernel::alloc::KBox;
78 /// use kernel::types::ForeignOwnable;
79 /// use kernel::sync::{LockClassKey, SpinLock};
80 /// use pin_init::stack_pin_init;
81 ///
82 /// let key = KBox::pin_init(LockClassKey::new_dynamic(), GFP_KERNEL)?;
83 /// let key_ptr = key.into_foreign();
84 ///
85 /// {
86 /// stack_pin_init!(let num: SpinLock<u32> = SpinLock::new(
87 /// 0,
88 /// c"my_spinlock",
89 /// // SAFETY: `key_ptr` is returned by the above `into_foreign()`, whose
90 /// // `from_foreign()` has not yet been called.
91 /// unsafe { <Pin<KBox<LockClassKey>> as ForeignOwnable>::borrow(key_ptr) }
92 /// ));
93 /// }
94 ///
95 /// // SAFETY: We dropped `num`, the only use of the key, so the result of the previous
96 /// // `borrow` has also been dropped. Thus, it's safe to use from_foreign.
97 /// unsafe { drop(<Pin<KBox<LockClassKey>> as ForeignOwnable>::from_foreign(key_ptr)) };
98 /// # Ok::<(), Error>(())
99 /// ```
100 pub fn new_dynamic() -> impl PinInit<Self> {
101 pin_init!(Self {
102 // SAFETY: lockdep_register_key expects an uninitialized block of memory
103 inner <- Opaque::ffi_init(|slot| unsafe { bindings::lockdep_register_key(slot) })
104 })
105 }
106
107 /// Returns a raw pointer to the inner C struct.
108 ///
109 /// It is up to the caller to use the raw pointer correctly.
110 pub fn as_ptr(&self) -> *mut bindings::lock_class_key {
111 self.inner.get()
112 }
113}
114
115#[pinned_drop]
116impl PinnedDrop for LockClassKey {
117 fn drop(self: Pin<&mut Self>) {
118 // SAFETY: `self.as_ptr()` was registered with lockdep and `self` is pinned, so the address
119 // hasn't changed. Thus, it's safe to pass it to unregister.
120 unsafe { bindings::lockdep_unregister_key(self.as_ptr()) }
121 }
122}
123
124/// Defines a new static lock class and returns a pointer to it.
125///
126/// # Examples
127///
128/// ```
129/// use kernel::sync::{static_lock_class, Arc, SpinLock};
130///
131/// fn new_locked_int() -> Result<Arc<SpinLock<u32>>> {
132/// Arc::pin_init(SpinLock::new(
133/// 42,
134/// c"new_locked_int",
135/// static_lock_class!(),
136/// ), GFP_KERNEL)
137/// }
138/// ```
139#[macro_export]
140macro_rules! static_lock_class {
141 () => {{
142 static CLASS: $crate::sync::LockClassKey =
143 // SAFETY: The returned `LockClassKey` is stored in static memory and we pin it. Drop
144 // never runs on a static global.
145 unsafe { $crate::sync::LockClassKey::new_static() };
146 $crate::prelude::Pin::static_ref(&CLASS)
147 }};
148}
149pub use static_lock_class;
150
151/// Returns the given string, if one is provided, otherwise generates one based on the source code
152/// location.
153#[doc(hidden)]
154#[macro_export]
155macro_rules! optional_name {
156 () => {
157 $crate::c_str!(::core::concat!(::core::file!(), ":", ::core::line!()))
158 };
159 ($name:literal) => {
160 $crate::c_str!($name)
161 };
162}