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// SPDX-License-Identifier: GPL-2.0
//! RCU support.
//!
//! C header: [`include/linux/rcupdate.h`](../../../../include/linux/rcupdate.h)
use crate::bindings;
use core::marker::PhantomData;
/// Evidence that the RCU read side lock is held on the current thread/CPU.
///
/// The type is explicitly not `Send` because this property is per-thread/CPU.
///
/// # Invariants
///
/// The RCU read side lock is actually held while instances of this guard exist.
pub struct Guard {
_not_send: PhantomData<*mut ()>,
}
impl Guard {
/// Acquires the RCU read side lock and returns a guard.
pub fn new() -> Self {
// SAFETY: An FFI call with no additional requirements.
unsafe { bindings::rcu_read_lock() };
// INVARIANT: The RCU read side lock was just acquired above.
Self {
_not_send: PhantomData,
}
}
/// Explicitly releases the RCU read side lock.
pub fn unlock(self) {}
}
impl Default for Guard {
fn default() -> Self {
Self::new()
}
}
impl Drop for Guard {
fn drop(&mut self) {
// SAFETY: By the type invariants, the rcu read side is locked, so it is ok to unlock it.
unsafe { bindings::rcu_read_unlock() };
}
}
/// Acquires the RCU read side lock.
pub fn read_lock() -> Guard {
Guard::new()
}