[PATCH 1/3] rust: sync: Add abstraction for synchronize_rcu()

[Philipp Stanner <phasta@kernel.org>]

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>
---
 rust/kernel/sync/rcu.rs | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/rust/kernel/sync/rcu.rs b/rust/kernel/sync/rcu.rs
index a32bef6e490b..9b9addf8fedf 100644
--- a/rust/kernel/sync/rcu.rs
+++ b/rust/kernel/sync/rcu.rs
@@ -50,3 +50,11 @@ fn drop(&mut self) {
 pub fn read_lock() -> Guard {
     Guard::new()
 }
+
+/// Wait for one RCU grace period.
+///
+/// You typically do this to wait for everyone holding a [`Guard`].
+pub fn synchronize_rcu() {
+    // SAFETY: `synchronize_rcu()` is always safe to be called. It just waits for a grace period.
+    unsafe { bindings::synchronize_rcu() };
+}
-- 
2.54.0