fix(clique step_service): remove needless Arc

ethcore/src/engines/clique/mod.rs

@@ -168,7 +168,7 @@ pub struct Clique {
 	block_state_by_hash: RwLock<LruCache<H256, CliqueBlockState>>,
 	proposals: RwLock<HashMap<Address, VoteType>>,
 	signer: RwLock<Option<Box<EngineSigner>>>,
-	step_service: Option<Arc<StepService>>,
+	step_service: Option<StepService>,
 }
 
 #[cfg(test)]
@@ -181,7 +181,7 @@ pub struct Clique {
 	pub block_state_by_hash: RwLock<LruCache<H256, CliqueBlockState>>,
 	pub proposals: RwLock<HashMap<Address, VoteType>>,
 	pub signer: RwLock<Option<Box<EngineSigner>>>,
-	pub step_service: Option<Arc<StepService>>,
+	pub step_service: Option<StepService>,
 }
 
 impl Clique {
@@ -745,10 +745,10 @@ impl Engine<EthereumMachine> for Clique {
 	}
 
 	fn stop(&mut self) {
-		if let Some(mut s) = self.step_service.as_mut() {
-			Arc::get_mut(&mut s).map(|x| x.stop());
+		if let Some(step_service) = self.step_service.as_mut() {
+			step_service.stop();
 		} else {
-			warn!(target: "engine", "Stopping `CliqueStepService` failed requires mutable access");
+			warn!(target: "engine", "Attempted to stop StepService but it does nothing; no step service registered");
 		}
 	}
 

ethcore/src/engines/clique/step_service.rs

@@ -32,7 +32,7 @@ pub struct StepService {
 
 impl StepService {
 	/// Start the `StepService`
-	pub fn start<M: Machine + 'static>(engine: Weak<Engine<M>>) -> Arc<Self> {
+	pub fn start<M: Machine + 'static>(engine: Weak<Engine<M>>) -> Self {
 		let shutdown = Arc::new(AtomicBool::new(false));
 		let s = shutdown.clone();
 
@@ -60,10 +60,10 @@ impl StepService {
 				trace!(target: "miner", "CliqueStepService: shutdown.");
 			}).expect("CliqueStepService thread failed");
 
-		Arc::new(StepService {
+		StepService {
 			shutdown: s,
 			thread: Some(thread),
-		})
+		}
 	}
 
 	/// Stop the `StepService`