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 completion;
14mod condvar;
15pub mod lock;
16mod locked_by;
17pub mod poll;
18pub mod rcu;
19
20pub use arc::{Arc, ArcBorrow, UniqueArc};
21pub use completion::Completion;
22pub use condvar::{new_condvar, CondVar, CondVarTimeoutResult};
23pub use lock::global::{global_lock, GlobalGuard, GlobalLock, GlobalLockBackend, GlobalLockedBy};
24pub use lock::mutex::{new_mutex, Mutex, MutexGuard};
25pub use lock::spinlock::{new_spinlock, SpinLock, SpinLockGuard};
26pub use locked_by::LockedBy;
27
28/// Represents a lockdep class. It's a wrapper around C's `lock_class_key`.
29#[repr(transparent)]
30#[pin_data(PinnedDrop)]
31pub struct LockClassKey {
32    #[pin]
33    inner: Opaque<bindings::lock_class_key>,
34}
35
36// SAFETY: `bindings::lock_class_key` is designed to be used concurrently from multiple threads and
37// provides its own synchronization.
38unsafe impl Sync for LockClassKey {}
39
40impl LockClassKey {
41    /// Initializes a dynamically allocated lock class key. In the common case of using a
42    /// statically allocated lock class key, the static_lock_class! macro should be used instead.
43    ///
44    /// # Example
45    /// ```
46    /// # use kernel::c_str;
47    /// # use kernel::alloc::KBox;
48    /// # use kernel::types::ForeignOwnable;
49    /// # use kernel::sync::{LockClassKey, SpinLock};
50    /// # use pin_init::stack_pin_init;
51    ///
52    /// let key = KBox::pin_init(LockClassKey::new_dynamic(), GFP_KERNEL)?;
53    /// let key_ptr = key.into_foreign();
54    ///
55    /// {
56    ///     stack_pin_init!(let num: SpinLock<u32> = SpinLock::new(
57    ///         0,
58    ///         c_str!("my_spinlock"),
59    ///         // SAFETY: `key_ptr` is returned by the above `into_foreign()`, whose
60    ///         // `from_foreign()` has not yet been called.
61    ///         unsafe { <Pin<KBox<LockClassKey>> as ForeignOwnable>::borrow(key_ptr) }
62    ///     ));
63    /// }
64    ///
65    /// // SAFETY: We dropped `num`, the only use of the key, so the result of the previous
66    /// // `borrow` has also been dropped. Thus, it's safe to use from_foreign.
67    /// unsafe { drop(<Pin<KBox<LockClassKey>> as ForeignOwnable>::from_foreign(key_ptr)) };
68    ///
69    /// # Ok::<(), Error>(())
70    /// ```
71    pub fn new_dynamic() -> impl PinInit<Self> {
72        pin_init!(Self {
73            // SAFETY: lockdep_register_key expects an uninitialized block of memory
74            inner <- Opaque::ffi_init(|slot| unsafe { bindings::lockdep_register_key(slot) })
75        })
76    }
77
78    pub(crate) fn as_ptr(&self) -> *mut bindings::lock_class_key {
79        self.inner.get()
80    }
81}
82
83#[pinned_drop]
84impl PinnedDrop for LockClassKey {
85    fn drop(self: Pin<&mut Self>) {
86        // SAFETY: self.as_ptr was registered with lockdep and self is pinned, so the address
87        // hasn't changed. Thus, it's safe to pass to unregister.
88        unsafe { bindings::lockdep_unregister_key(self.as_ptr()) }
89    }
90}
91
92/// Defines a new static lock class and returns a pointer to it.
93#[doc(hidden)]
94#[macro_export]
95macro_rules! static_lock_class {
96    () => {{
97        static CLASS: $crate::sync::LockClassKey =
98            // SAFETY: lockdep expects uninitialized memory when it's handed a statically allocated
99            // lock_class_key
100            unsafe { ::core::mem::MaybeUninit::uninit().assume_init() };
101        $crate::prelude::Pin::static_ref(&CLASS)
102    }};
103}
104
105/// Returns the given string, if one is provided, otherwise generates one based on the source code
106/// location.
107#[doc(hidden)]
108#[macro_export]
109macro_rules! optional_name {
110    () => {
111        $crate::c_str!(::core::concat!(::core::file!(), ":", ::core::line!()))
112    };
113    ($name:literal) => {
114        $crate::c_str!($name)
115    };
116}
kernel/sync.rs

kernel/
sync.rs
