// SPDX-License-Identifier: GPL-2.0 //! RCU support. //! //! C header: [`include/linux/rcupdate.h`](srctree/include/linux/rcupdate.h) use crate::{bindings, types::NotThreadSafe}; /// 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(NotThreadSafe); 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(NotThreadSafe) } /// 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() }