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 completion;
15mod condvar;
16pub mod lock;
17mod locked_by;
18pub mod poll;
19pub mod rcu;
20
21pub use arc::{Arc, ArcBorrow, UniqueArc};
22pub use completion::Completion;
23pub use condvar::{new_condvar, CondVar, CondVarTimeoutResult};
24pub use lock::global::{global_lock, GlobalGuard, GlobalLock, GlobalLockBackend, GlobalLockedBy};
25pub use lock::mutex::{new_mutex, Mutex, MutexGuard};
26pub use lock::spinlock::{new_spinlock, SpinLock, SpinLockGuard};
27pub use locked_by::LockedBy;
28
29/// Represents a lockdep class. It's a wrapper around C's `lock_class_key`.
30#[repr(transparent)]
31#[pin_data(PinnedDrop)]
32pub struct LockClassKey {
33 #[pin]
34 inner: Opaque<bindings::lock_class_key>,
35}
36
37// SAFETY: `bindings::lock_class_key` is designed to be used concurrently from multiple threads and
38// provides its own synchronization.
39unsafe impl Sync for LockClassKey {}
40
41impl LockClassKey {
42 /// Initializes a dynamically allocated lock class key. In the common case of using a
43 /// statically allocated lock class key, the static_lock_class! macro should be used instead.
44 ///
45 /// # Examples
46 /// ```
47 /// # use kernel::c_str;
48 /// # use kernel::alloc::KBox;
49 /// # use kernel::types::ForeignOwnable;
50 /// # use kernel::sync::{LockClassKey, SpinLock};
51 /// # use pin_init::stack_pin_init;
52 ///
53 /// let key = KBox::pin_init(LockClassKey::new_dynamic(), GFP_KERNEL)?;
54 /// let key_ptr = key.into_foreign();
55 ///
56 /// {
57 /// stack_pin_init!(let num: SpinLock<u32> = SpinLock::new(
58 /// 0,
59 /// c_str!("my_spinlock"),
60 /// // SAFETY: `key_ptr` is returned by the above `into_foreign()`, whose
61 /// // `from_foreign()` has not yet been called.
62 /// unsafe { <Pin<KBox<LockClassKey>> as ForeignOwnable>::borrow(key_ptr) }
63 /// ));
64 /// }
65 ///
66 /// // SAFETY: We dropped `num`, the only use of the key, so the result of the previous
67 /// // `borrow` has also been dropped. Thus, it's safe to use from_foreign.
68 /// unsafe { drop(<Pin<KBox<LockClassKey>> as ForeignOwnable>::from_foreign(key_ptr)) };
69 ///
70 /// # Ok::<(), Error>(())
71 /// ```
72 pub fn new_dynamic() -> impl PinInit<Self> {
73 pin_init!(Self {
74 // SAFETY: lockdep_register_key expects an uninitialized block of memory
75 inner <- Opaque::ffi_init(|slot| unsafe { bindings::lockdep_register_key(slot) })
76 })
77 }
78
79 pub(crate) fn as_ptr(&self) -> *mut bindings::lock_class_key {
80 self.inner.get()
81 }
82}
83
84#[pinned_drop]
85impl PinnedDrop for LockClassKey {
86 fn drop(self: Pin<&mut Self>) {
87 // SAFETY: self.as_ptr was registered with lockdep and self is pinned, so the address
88 // hasn't changed. Thus, it's safe to pass to unregister.
89 unsafe { bindings::lockdep_unregister_key(self.as_ptr()) }
90 }
91}
92
93/// Defines a new static lock class and returns a pointer to it.
94#[doc(hidden)]
95#[macro_export]
96macro_rules! static_lock_class {
97 () => {{
98 static CLASS: $crate::sync::LockClassKey =
99 // Lockdep expects uninitialized memory when it's handed a statically allocated `struct
100 // lock_class_key`.
101 //
102 // SAFETY: `LockClassKey` transparently wraps `Opaque` which permits uninitialized
103 // memory.
104 unsafe { ::core::mem::MaybeUninit::uninit().assume_init() };
105 $crate::prelude::Pin::static_ref(&CLASS)
106 }};
107}
108
109/// Returns the given string, if one is provided, otherwise generates one based on the source code
110/// location.
111#[doc(hidden)]
112#[macro_export]
113macro_rules! optional_name {
114 () => {
115 $crate::c_str!(::core::concat!(::core::file!(), ":", ::core::line!()))
116 };
117 ($name:literal) => {
118 $crate::c_str!($name)
119 };
120}