From a1265d6af961a207a16ea3d7374eec3c2632aed7 Mon Sep 17 00:00:00 2001 From: Wedson Almeida Filho Date: Mon, 4 Sep 2023 13:21:40 +0200 Subject: rust: add rcu abstraction Add a simple abstraction to guard critical code sections with an rcu read lock. Co-developed-by: Andreas Hindborg Signed-off-by: Andreas Hindborg Signed-off-by: Wedson Almeida Filho Signed-off-by: Danilo Krummrich --- rust/helpers.c | 15 ++++++++++++++ rust/kernel/sync.rs | 1 + rust/kernel/sync/rcu.rs | 52 +++++++++++++++++++++++++++++++++++++++++++++++++ 3 files changed, 68 insertions(+) create mode 100644 rust/kernel/sync/rcu.rs diff --git a/rust/helpers.c b/rust/helpers.c index 92d3c03ae1bd..9b64f0a6fe3a 100644 --- a/rust/helpers.c +++ b/rust/helpers.c @@ -29,6 +29,7 @@ #include #include #include +#include #include #include #include @@ -200,6 +201,20 @@ rust_helper_krealloc(const void *objp, size_t new_size, gfp_t flags) } EXPORT_SYMBOL_GPL(rust_helper_krealloc); +/* rcu */ +void rust_helper_rcu_read_lock(void) +{ + rcu_read_lock(); +} +EXPORT_SYMBOL_GPL(rust_helper_rcu_read_lock); + +void rust_helper_rcu_read_unlock(void) +{ + rcu_read_unlock(); +} +EXPORT_SYMBOL_GPL(rust_helper_rcu_read_unlock); +/* end rcu */ + /* * `bindgen` binds the C `size_t` type as the Rust `usize` type, so we can * use it in contexts where Rust expects a `usize` like slice (array) indices. diff --git a/rust/kernel/sync.rs b/rust/kernel/sync.rs index 0ab20975a3b5..1806767359fe 100644 --- a/rust/kernel/sync.rs +++ b/rust/kernel/sync.rs @@ -11,6 +11,7 @@ mod arc; mod condvar; pub mod lock; mod locked_by; +pub mod rcu; pub use arc::{Arc, ArcBorrow, UniqueArc}; pub use condvar::{new_condvar, CondVar, CondVarTimeoutResult}; diff --git a/rust/kernel/sync/rcu.rs b/rust/kernel/sync/rcu.rs new file mode 100644 index 000000000000..5a35495f69a4 --- /dev/null +++ b/rust/kernel/sync/rcu.rs @@ -0,0 +1,52 @@ +// SPDX-License-Identifier: GPL-2.0 + +//! RCU support. +//! +//! C header: [`include/linux/rcupdate.h`](srctree/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() +} -- cgit v1.2.3-58-ga151