rust: sync: Add abstraction for synchronize_rcu()

synchronize_rcu() is a frequently used C function which is always safe
to be called.

Add a safe abstraction for synchronize_rcu().

Signed-off-by: Philipp Stanner <phasta@kernel.org>
Reviewed-by: Onur Özkan <work@onurozkan.dev>
Reviewed-by: Danilo Krummrich <dakr@kernel.org>
Reviewed-by: Gary Guo <gary@garyguo.net>
[boqun: Fix rustdoc reported by kernel test robot <lkp@intel.com>]
Signed-off-by: Boqun Feng <boqun@kernel.org>
Link: https://patch.msgid.link/20260624150704.1504001-3-phasta@kernel.org

1 files changed, 16 insertions, 0 deletions

diff --git a/rust/kernel/sync/rcu.rs b/rust/kernel/sync/rcu.rs
index a32bef6e490b..d867240be736 100644
--- a/rust/kernel/sync/rcu.rs
+++ b/rust/kernel/sync/rcu.rs
@@ -50,3 +50,19 @@ impl Drop for Guard {
 pub fn read_lock() -> Guard {
     Guard::new()
 }
+
+/// Wait for one RCU grace period.
+///
+/// Waits for all RCU read-side critical sections (such as those established by
+/// a [`Guard`]) at the moment of the function call to finish.
+///
+/// Does not prevent new read-side critical sections from starting, which may
+/// begin and run while this call is blocking.
+///
+/// Note that this is one of the RCU primitives which must not be called in
+/// atomic context.
+#[inline]
+pub fn synchronize_rcu() {
+    // SAFETY: `synchronize_rcu()` is always safe to be called from process context.
+    unsafe { bindings::synchronize_rcu() };
+}