Fix possible deadlock

- Removing some sync blocks which imho
  are not needed anymore.
- Adding some smoke tests.
- Relates to #364

spring-statemachine-core/src/main/java/org/springframework/statemachine/support/AbstractStateMachine.java

@@ -115,9 +115,6 @@ public abstract class AbstractStateMachine<S, E> extends StateMachineObjectSuppo
 
 	private volatile Message<E> forwardedInitialEvent;
 
-	private final Object lock = new Object();
-	private final Object lock2 = new Object();
-
 	private StateMachine<S, E> parentMachine;
 
 	/**
@@ -177,12 +174,10 @@ public abstract class AbstractStateMachine<S, E> extends StateMachineObjectSuppo
 	public State<S,E> getState() {
 		// if we're complete assume we're stopped
 		// and state was stashed into lastState
-		synchronized (lock) {
-			if (lastState != null && isComplete()) {
-				return lastState;
-			} else {
-				return currentState;
-			}
+		if (lastState != null && isComplete()) {
+			return lastState;
+		} else {
+			return currentState;
 		}
 	}
 
@@ -212,9 +207,7 @@ public abstract class AbstractStateMachine<S, E> extends StateMachineObjectSuppo
 
 	@Override
 	public boolean sendEvent(Message<E> event) {
-		synchronized (lock2) {
-			return sendEventInternal(event);
-		}
+		return sendEventInternal(event);
 	}
 
 	@Override
@@ -381,15 +374,13 @@ public abstract class AbstractStateMachine<S, E> extends StateMachineObjectSuppo
 
 	@Override
 	protected void doStop() {
-		synchronized (lock) {
-			stateMachineExecutor.stop();
-			notifyStateMachineStopped(buildStateContext(Stage.STATEMACHINE_STOP, null, null, this));
-			// stash current state before we null it so that
-			// we can still return where we 'were' when machine is stopped
-			lastState = currentState;
-			currentState = null;
-			initialEnabled = null;
-		}
+		stateMachineExecutor.stop();
+		notifyStateMachineStopped(buildStateContext(Stage.STATEMACHINE_STOP, null, null, this));
+		// stash current state before we null it so that
+		// we can still return where we 'were' when machine is stopped
+		lastState = currentState;
+		currentState = null;
+		initialEnabled = null;
 	}
 
 	@Override
@@ -938,9 +929,7 @@ public abstract class AbstractStateMachine<S, E> extends StateMachineObjectSuppo
 
 	void setCurrentState(State<S, E> state, Message<E> message, Transition<S, E> transition, boolean exit,
 			StateMachine<S, E> stateMachine, Collection<State<S, E>> sources, Collection<State<S, E>> targets) {
-		synchronized (lock2) {
-			setCurrentStateInternal(state, message, transition, exit, stateMachine, sources, targets);
-		}
+		setCurrentStateInternal(state, message, transition, exit, stateMachine, sources, targets);
 	}
 
 	private void setCurrentStateInternal(State<S, E> state, Message<E> message, Transition<S, E> transition, boolean exit,

spring-statemachine-core/src/test/java/org/springframework/statemachine/StateMachineSmokeTests.java

@@ -0,0 +1,95 @@
+/*
+ * Copyright 2017 the original author or authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.springframework.statemachine;
+
+import static org.hamcrest.CoreMatchers.nullValue;
+import static org.hamcrest.Matchers.notNullValue;
+import static org.junit.Assert.assertThat;
+import static org.junit.Assert.assertTrue;
+
+import org.junit.Test;
+import org.springframework.context.annotation.AnnotationConfigApplicationContext;
+import org.springframework.context.annotation.Configuration;
+import org.springframework.statemachine.config.EnableStateMachine;
+import org.springframework.statemachine.config.EnumStateMachineConfigurerAdapter;
+import org.springframework.statemachine.config.builders.StateMachineStateConfigurer;
+import org.springframework.statemachine.config.builders.StateMachineTransitionConfigurer;
+
+public class StateMachineSmokeTests extends AbstractStateMachineTests {
+
+	@Override
+	protected AnnotationConfigApplicationContext buildContext() {
+		return new AnnotationConfigApplicationContext();
+	}
+
+	@Test(timeout = 10000)
+	public void testLifecycleThreading() throws Exception {
+		context.register(Config1.class);
+		context.refresh();
+		assertTrue(context.containsBean(StateMachineSystemConstants.DEFAULT_ID_STATEMACHINE));
+		@SuppressWarnings("unchecked")
+		ObjectStateMachine<TestStates,TestEvents> machine =
+				context.getBean(StateMachineSystemConstants.DEFAULT_ID_STATEMACHINE, ObjectStateMachine.class);
+		assertThat(machine, notNullValue());
+
+		int cnt = 10;
+		Thread[] threads = new Thread[cnt];
+		for (int i = 0; i < cnt; i++) {
+			threads[i] = new Thread(() -> {
+				for (int j = 0; j < 1000; j++) {
+					machine.start();
+					machine.sendEvent(TestEvents.E1);
+					machine.stop();
+				}
+			});
+		}
+		for (Thread t : threads) {
+			t.start();
+		}
+		for (Thread t : threads) {
+			t.join();
+		}
+		assertThat(machine.getState(), nullValue());
+	}
+
+	@Configuration
+	@EnableStateMachine
+	static class Config1 extends EnumStateMachineConfigurerAdapter<TestStates, TestEvents> {
+
+		@Override
+		public void configure(StateMachineStateConfigurer<TestStates, TestEvents> states) throws Exception {
+			states
+				.withStates()
+					.initial(TestStates.S1)
+					.state(TestStates.S2);
+		}
+
+		@Override
+		public void configure(StateMachineTransitionConfigurer<TestStates, TestEvents> transitions) throws Exception {
+			transitions
+				.withExternal()
+					.source(TestStates.S1)
+					.target(TestStates.S2)
+					.event(TestEvents.E1)
+					.and()
+				.withExternal()
+					.source(TestStates.S2)
+					.target(TestStates.S1)
+					.event(TestEvents.E1);
+		}
+	}
+
+}

spring-statemachine-samples/persist/src/test/java/demo/persist/PersistTests.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2015 the original author or authors.
+ * Copyright 2015-2017 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -89,6 +89,25 @@ public class PersistTests {
 		assertThat(persist.listDbEntries(), containsString("id=2, state=SENT"));
 	}
 
+	@Test
+	public void testThreadingSmoke() throws Exception {
+		int cnt = 10;
+		Thread[] threads = new Thread[cnt];
+		for (int i = 0; i < cnt; i++) {
+			threads[i] = new Thread(() -> {
+				for (int j = 0; j < 1000; j++) {
+					persist.change(3, "SEND");
+				}
+			});
+		}
+		for (Thread t : threads) {
+			t.start();
+		}
+		for (Thread t : threads) {
+			t.join();
+		}
+	}
+
 	private static class TestListener extends StateMachineListenerAdapter<String, String> {
 
 		volatile CountDownLatch stateChangedLatch = new CountDownLatch(1);