kernel/sync/
rcu.rs

1// SPDX-License-Identifier: GPL-2.0
2
3//! RCU support.
4//!
5//! C header: [`include/linux/rcupdate.h`](srctree/include/linux/rcupdate.h)
6
7use crate::{bindings, types::NotThreadSafe};
8
9/// Evidence that the RCU read side lock is held on the current thread/CPU.
10///
11/// The type is explicitly not `Send` because this property is per-thread/CPU.
12///
13/// # Invariants
14///
15/// The RCU read side lock is actually held while instances of this guard exist.
16pub struct Guard(NotThreadSafe);
17
18impl Guard {
19    /// Acquires the RCU read side lock and returns a guard.
20    pub fn new() -> Self {
21        // SAFETY: An FFI call with no additional requirements.
22        unsafe { bindings::rcu_read_lock() };
23        // INVARIANT: The RCU read side lock was just acquired above.
24        Self(NotThreadSafe)
25    }
26
27    /// Explicitly releases the RCU read side lock.
28    pub fn unlock(self) {}
29}
30
31impl Default for Guard {
32    fn default() -> Self {
33        Self::new()
34    }
35}
36
37impl Drop for Guard {
38    fn drop(&mut self) {
39        // SAFETY: By the type invariants, the RCU read side is locked, so it is ok to unlock it.
40        unsafe { bindings::rcu_read_unlock() };
41    }
42}
43
44/// Acquires the RCU read side lock.
45pub fn read_lock() -> Guard {
46    Guard::new()
47}
kernel/sync/rcu.rs

kernel/sync/
rcu.rs
