[PATCH v4 3/5] rust: sync: Add abstraction for rcu_barrier()

[Philipp Stanner <phasta@kernel.org>]

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

Add a safe abstraction for rcu_barrier().

Signed-off-by: Philipp Stanner <phasta@kernel.org>
---
 rust/kernel/sync/rcu.rs | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/rust/kernel/sync/rcu.rs b/rust/kernel/sync/rcu.rs
index a32bef6e490b..9196feb62d6d 100644
--- a/rust/kernel/sync/rcu.rs
+++ b/rust/kernel/sync/rcu.rs
@@ -50,3 +50,9 @@ fn drop(&mut self) {
 pub fn read_lock() -> Guard {
     Guard::new()
 }
+
+/// Wait for all pending [`bindings::call_rcu()`] callbacks, if there are any.
+pub fn rcu_barrier() {
+    // SAFETY: `rcu_barrier()` is always safe to be called. It just might wait for a grace period.
+    unsafe { bindings::rcu_barrier() };
+}
-- 
2.54.0