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}
kernel/sync.rs

kernel/
sync.rs
