strengthen signals-received atomics (#5132)

* strengthen signals-received atomics

* Update node/overseer/overseer-gen/src/lib.rs

Co-authored-by: Andrei Sandu <54316454+sandreim@users.noreply.github.com>

* fmt

Co-authored-by: Andrei Sandu <54316454+sandreim@users.noreply.github.com>

polkadot/node/overseer/overseer-gen/src/lib.rs

@@ -196,13 +196,15 @@ pub struct SignalsReceived(Arc<AtomicUsize>);
 impl SignalsReceived {
 	/// Load the current value of received signals.
 	pub fn load(&self) -> usize {
-		// off by a few is ok
-		self.0.load(atomic::Ordering::Relaxed)
+		// It's imperative that we prevent reading a stale value from memory because of reordering.
+		// Memory barrier to ensure that no reads or writes in the current thread before this load are reordered.
+		// All writes in other threads using release semantics become visible to the current thread.
+		self.0.load(atomic::Ordering::Acquire)
 	}
 
 	/// Increase the number of signals by one.
 	pub fn inc(&self) {
-		self.0.fetch_add(1, atomic::Ordering::Acquire);
+		self.0.fetch_add(1, atomic::Ordering::AcqRel);
 	}
 }