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([2a02:810d:4b3f:ee94:642:1aff:fe31:a19f]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-42028c7730dsm189604005e9.25.2024.05.20.10.27.02 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 20 May 2024 10:27:03 -0700 (PDT) From: Danilo Krummrich To: gregkh@linuxfoundation.org, rafael@kernel.org, bhelgaas@google.com, ojeda@kernel.org, alex.gaynor@gmail.com, wedsonaf@gmail.com, boqun.feng@gmail.com, gary@garyguo.net, bjorn3_gh@protonmail.com, benno.lossin@proton.me, a.hindborg@samsung.com, aliceryhl@google.com, airlied@gmail.com, fujita.tomonori@gmail.com, lina@asahilina.net, pstanner@redhat.com, ajanulgu@redhat.com, lyude@redhat.com Cc: rust-for-linux@vger.kernel.org, linux-kernel@vger.kernel.org, linux-pci@vger.kernel.org, Danilo Krummrich Subject: [RFC PATCH 03/11] rust: add rcu abstraction Date: Mon, 20 May 2024 19:25:40 +0200 Message-ID: <20240520172554.182094-4-dakr@redhat.com> X-Mailer: git-send-email 2.45.1 In-Reply-To: <20240520172554.182094-1-dakr@redhat.com> References: <20240520172554.182094-1-dakr@redhat.com> Precedence: bulk X-Mailing-List: linux-pci@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 From: Wedson Almeida Filho 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 f9d2db1d1f33..1d3e800140fc 100644 --- a/rust/helpers.c +++ b/rust/helpers.c @@ -27,6 +27,7 @@ #include #include #include +#include #include #include #include @@ -158,6 +159,20 @@ void rust_helper_init_work_with_key(struct work_struct *work, work_func_t func, } EXPORT_SYMBOL_GPL(rust_helper_init_work_with_key); +/* 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 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..1a1c8ea49359 --- /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`](../../../../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() +}