diff mbox series

[v5,04/16] rust: add rcu abstraction

Message ID 20241210224947.23804-5-dakr@kernel.org (mailing list archive)
State Superseded
Headers show
Series Device / Driver PCI / Platform Rust abstractions | expand

Commit Message

Danilo Krummrich Dec. 10, 2024, 10:46 p.m. UTC 
From: Wedson Almeida Filho <wedsonaf@gmail.com>

Add a simple abstraction to guard critical code sections with an rcu
read lock.

Signed-off-by: Wedson Almeida Filho <wedsonaf@gmail.com>
Co-developed-by: Danilo Krummrich <dakr@kernel.org>
Signed-off-by: Danilo Krummrich <dakr@kernel.org>
---
 rust/helpers/helpers.c  |  1 +
 rust/helpers/rcu.c      | 13 ++++++++++++
 rust/kernel/sync.rs     |  1 +
 rust/kernel/sync/rcu.rs | 47 +++++++++++++++++++++++++++++++++++++++++
 4 files changed, 62 insertions(+)
 create mode 100644 rust/helpers/rcu.c
 create mode 100644 rust/kernel/sync/rcu.rs

Comments

Boqun Feng Dec. 11, 2024, 6:47 p.m. UTC | #1 
Hi Danilo,

This looks good so far, could you please Cc RCU maintainers for the next
version (if there is one).

A few nits below, with or without, feel free to add:

Reviewed-by: Boqun Feng <boqun.feng@gmail.com>

On Tue, Dec 10, 2024 at 11:46:31PM +0100, Danilo Krummrich wrote:
> From: Wedson Almeida Filho <wedsonaf@gmail.com>
> 
> Add a simple abstraction to guard critical code sections with an rcu
> read lock.
> 
> Signed-off-by: Wedson Almeida Filho <wedsonaf@gmail.com>
> Co-developed-by: Danilo Krummrich <dakr@kernel.org>
> Signed-off-by: Danilo Krummrich <dakr@kernel.org>
> ---
>  rust/helpers/helpers.c  |  1 +
>  rust/helpers/rcu.c      | 13 ++++++++++++
>  rust/kernel/sync.rs     |  1 +
>  rust/kernel/sync/rcu.rs | 47 +++++++++++++++++++++++++++++++++++++++++
>  4 files changed, 62 insertions(+)
>  create mode 100644 rust/helpers/rcu.c
>  create mode 100644 rust/kernel/sync/rcu.rs
> 
> diff --git a/rust/helpers/helpers.c b/rust/helpers/helpers.c
> index dcf827a61b52..060750af6524 100644
> --- a/rust/helpers/helpers.c
> +++ b/rust/helpers/helpers.c
> @@ -20,6 +20,7 @@
>  #include "page.c"
>  #include "pid_namespace.c"
>  #include "rbtree.c"
> +#include "rcu.c"
>  #include "refcount.c"
>  #include "security.c"
>  #include "signal.c"
> diff --git a/rust/helpers/rcu.c b/rust/helpers/rcu.c
> new file mode 100644
> index 000000000000..f1cec6583513
> --- /dev/null
> +++ b/rust/helpers/rcu.c
> @@ -0,0 +1,13 @@
> +// SPDX-License-Identifier: GPL-2.0
> +
> +#include <linux/rcupdate.h>
> +
> +void rust_helper_rcu_read_lock(void)
> +{
> +	rcu_read_lock();
> +}
> +
> +void rust_helper_rcu_read_unlock(void)
> +{
> +	rcu_read_unlock();
> +}
> diff --git a/rust/kernel/sync.rs b/rust/kernel/sync.rs
> index 1eab7ebf25fd..0654008198b2 100644
> --- a/rust/kernel/sync.rs
> +++ b/rust/kernel/sync.rs
> @@ -12,6 +12,7 @@
>  pub mod lock;
>  mod locked_by;
>  pub mod poll;
> +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..3beef70d5f34
> --- /dev/null
> +++ b/rust/kernel/sync/rcu.rs
> @@ -0,0 +1,47 @@
> +// 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.

s/rcu/RCU

when referring the RCU mechanism or the subsystem, it makes sense to use
the capitalized abbreviation.

Regards,
Boqun

> +        unsafe { bindings::rcu_read_unlock() };
> +    }
> +}
> +
> +/// Acquires the RCU read side lock.
> +pub fn read_lock() -> Guard {
> +    Guard::new()
> +}
> -- 
> 2.47.0
>
diff mbox series

Patch

diff --git a/rust/helpers/helpers.c b/rust/helpers/helpers.c
index dcf827a61b52..060750af6524 100644
--- a/rust/helpers/helpers.c
+++ b/rust/helpers/helpers.c
@@ -20,6 +20,7 @@ 
 #include "page.c"
 #include "pid_namespace.c"
 #include "rbtree.c"
+#include "rcu.c"
 #include "refcount.c"
 #include "security.c"
 #include "signal.c"
diff --git a/rust/helpers/rcu.c b/rust/helpers/rcu.c
new file mode 100644
index 000000000000..f1cec6583513
--- /dev/null
+++ b/rust/helpers/rcu.c
@@ -0,0 +1,13 @@ 
+// SPDX-License-Identifier: GPL-2.0
+
+#include <linux/rcupdate.h>
+
+void rust_helper_rcu_read_lock(void)
+{
+	rcu_read_lock();
+}
+
+void rust_helper_rcu_read_unlock(void)
+{
+	rcu_read_unlock();
+}
diff --git a/rust/kernel/sync.rs b/rust/kernel/sync.rs
index 1eab7ebf25fd..0654008198b2 100644
--- a/rust/kernel/sync.rs
+++ b/rust/kernel/sync.rs
@@ -12,6 +12,7 @@ 
 pub mod lock;
 mod locked_by;
 pub mod poll;
+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..3beef70d5f34
--- /dev/null
+++ b/rust/kernel/sync/rcu.rs
@@ -0,0 +1,47 @@ 
+// 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()
+}