diff --git a/plugins/org.eclipse.xtext.ide/src/org/eclipse/xtext/ide/server/concurrent/RequestCancelIndicator.xtend b/plugins/org.eclipse.xtext.ide/src/org/eclipse/xtext/ide/server/concurrent/RequestCancelIndicator.xtend
index 5e54645db..8f6474eba 100644
--- a/plugins/org.eclipse.xtext.ide/src/org/eclipse/xtext/ide/server/concurrent/RequestCancelIndicator.xtend
+++ b/plugins/org.eclipse.xtext.ide/src/org/eclipse/xtext/ide/server/concurrent/RequestCancelIndicator.xtend
@@ -13,12 +13,12 @@ import org.eclipse.xtend.lib.annotations.Accessors
  * @author kosyakov - Initial contribution and API
  */
 class RequestCancelIndicator implements CancellableIndicator {
-	
+
 	@Accessors(PUBLIC_GETTER)
-	boolean canceled
-	
+	volatile boolean canceled
+
 	override cancel() {
 		canceled = true
 	}
 
-}
\ No newline at end of file
+}
diff --git a/plugins/org.eclipse.xtext.ide/src/org/eclipse/xtext/ide/server/concurrent/RequestManager.xtend b/plugins/org.eclipse.xtext.ide/src/org/eclipse/xtext/ide/server/concurrent/RequestManager.xtend
index d3c170175..e71d7c271 100644
--- a/plugins/org.eclipse.xtext.ide/src/org/eclipse/xtext/ide/server/concurrent/RequestManager.xtend
+++ b/plugins/org.eclipse.xtext.ide/src/org/eclipse/xtext/ide/server/concurrent/RequestManager.xtend
@@ -39,50 +39,77 @@ class RequestManager {
 
 	val semaphore = new Semaphore(MAX_PERMITS)
 
+	def void shutdown() {
+		readExecutorService.shutdown()
+		writeExecutorService.shutdown()
+	}
+
 	def CompletableFuture<Void> runWrite((CancelIndicator)=>void writeRequest) {
 		return runWrite(writeRequest, new RequestCancelIndicator)
 	}
 
+	/**
+	 * <p>
+	 * The given <i>write request</i> will be ran first when <i>all running requests</i> completed.
+	 * </p>
+	 * <p>
+	 * Currently <i>running requests</i> will be cancelled.
+	 * </p>
+	 * <p>
+	 * A provided cancel indicator should implement {@link org.eclipse.xtext.ide.server.concurrent.CancellableIndicator CancellableIndicator} 
+	 * to let the given request to be cancelled by a write request.
+	 * </p>
+	 */
 	def CompletableFuture<Void> runWrite((CancelIndicator)=>void writeRequest, CancelIndicator cancelIndicator) {
 		cancelIndicators.forEach[cancel]
+
+		if (cancelIndicator instanceof CancellableIndicator)
+			cancelIndicators += cancelIndicator
+
 		return CompletableFuture.runAsync([
-			writeRequest.withVoidAsReturnType.run(MAX_PERMITS, cancelIndicator)
-		], writeExecutorService)
+			semaphore.acquire(MAX_PERMITS)
+			try {
+				writeRequest.apply(cancelIndicator)
+			} finally {
+				semaphore.release(MAX_PERMITS)
+			}
+		], writeExecutorService).whenComplete [
+			if (cancelIndicator instanceof CancellableIndicator)
+				cancelIndicators -= cancelIndicator
+		]
 	}
 
 	def <V> CompletableFuture<V> runRead((CancelIndicator)=>V readRequest) {
 		return runRead(readRequest, new RequestCancelIndicator)
 	}
 
+	/**
+	 * <p>
+	 * The given <i>read request</i> will be ran:
+	 * <ul>
+	 * 	<li>concurrent with <i>running read requests</i>;</li>
+	 * 	<li>first when <i>running write requests</i> completed.</li>
+	 * </ul>
+	 * </p>
+	 * <p>
+	 * A provided cancel indicator should implement {@link org.eclipse.xtext.ide.server.concurrent.CancellableIndicator CancellableIndicator} 
+	 * to let the given request to be cancelled by a write request.
+	 * </p>
+	 */
 	def <V> CompletableFuture<V> runRead((CancelIndicator)=>V readRequest, CancelIndicator cancelIndicator) {
+		if (cancelIndicator instanceof CancellableIndicator)
+			cancelIndicators += cancelIndicator
+
 		return CompletableFuture.supplyAsync([
-			readRequest.run(1, cancelIndicator)
-		], readExecutorService)
-	}
-
-	protected def <V> V run(
-		(CancelIndicator)=>V request,
-		int permits,
-		CancelIndicator cancelIndicator
-	) {
-		semaphore.acquire(permits)
-		try {
-			if (cancelIndicator instanceof CancellableIndicator)
-				cancelIndicators += cancelIndicator
-
-			return request.apply(cancelIndicator)
-		} finally {
+			semaphore.acquire(1)
+			try {
+				return readRequest.apply(cancelIndicator)
+			} finally {
+				semaphore.release(1)
+			}
+		], readExecutorService).whenComplete [
 			if (cancelIndicator instanceof CancellableIndicator)
 				cancelIndicators -= cancelIndicator
-
-			semaphore.release(permits)
-		}
-	}
-
-	protected def (CancelIndicator)=>Void withVoidAsReturnType((CancelIndicator)=>void request) {
-		return [ cancelIindicator |
-			request.apply(cancelIindicator)
-			return null
 		]
 	}
 
diff --git a/tests/org.eclipse.xtext.ide.tests/src/org/eclipse/xtext/ide/tests/server/concurrent/RequestManagerTest.xtend b/tests/org.eclipse.xtext.ide.tests/src/org/eclipse/xtext/ide/tests/server/concurrent/RequestManagerTest.xtend
new file mode 100644
index 000000000..7c7d6fbfd
--- /dev/null
+++ b/tests/org.eclipse.xtext.ide.tests/src/org/eclipse/xtext/ide/tests/server/concurrent/RequestManagerTest.xtend
@@ -0,0 +1,142 @@
+/*******************************************************************************
+ * Copyright (c) 2016 TypeFox GmbH (http://www.typefox.io) and others.
+ * All rights reserved. This program and the accompanying materials
+ * are made available under the terms of the Eclipse Public License v1.0
+ * which accompanies this distribution, and is available at
+ * http://www.eclipse.org/legal/epl-v10.html
+ *******************************************************************************/
+package org.eclipse.xtext.ide.tests.server.concurrent
+
+import com.google.inject.Guice
+import com.google.inject.Inject
+import java.util.concurrent.atomic.AtomicInteger
+import org.eclipse.xtext.ide.server.ServerModule
+import org.eclipse.xtext.ide.server.concurrent.RequestManager
+import org.junit.After
+import org.junit.Before
+import org.junit.Test
+
+import static org.junit.Assert.*
+
+/**
+ * @author kosyakov - Initial contribution and API
+ */
+class RequestManagerTest {
+
+	@Inject
+	RequestManager requestManager
+
+	AtomicInteger sharedState
+
+	@Before
+	def void setUp() {
+		sharedState = new AtomicInteger
+		Guice.createInjector(new ServerModule).injectMembers(this)
+	}
+
+	@After
+	def void tearDown() {
+		requestManager.shutdown
+		sharedState = null
+	}
+
+	@Test
+	def void testRunRead() {
+		val future = requestManager.runRead [
+			'Foo'
+		]
+		assertEquals('Foo', future.get)
+	}
+
+	@Test
+	def void testRunReadConcurrent() {
+		val future = requestManager.runRead [
+			while (sharedState.get == 0) {
+			}
+			sharedState.incrementAndGet
+		]
+		val future2 = requestManager.runRead [
+			sharedState.incrementAndGet
+		]
+		future2.join
+		future.join
+		assertEquals(2, sharedState.get)
+	}
+
+	@Test
+	def void testRunReadAfterWrite() {
+		requestManager.runWrite [
+			while (sharedState.get == 0) {
+			}
+			sharedState.incrementAndGet
+		]
+		val future = requestManager.runRead [
+			sharedState.get
+		]
+		sharedState.incrementAndGet
+		assertEquals(2, future.get)
+	}
+
+	@Test
+	def void testRunWrite() {
+		requestManager.runWrite [
+			sharedState.incrementAndGet
+		].join
+		assertEquals(1, sharedState.get)
+	}
+
+	@Test
+	def void testRunWriteAfterWrite() {
+		val future = requestManager.runWrite [
+			sharedState.incrementAndGet
+		]
+		val future2 = requestManager.runWrite [
+			if (sharedState.get != 0)
+				sharedState.incrementAndGet
+		]
+		future2.join
+		future.join
+		assertEquals(2, sharedState.get)
+	}
+
+	@Test
+	def void testRunWriteAfterRead() {
+		requestManager.runRead [
+			sharedState.incrementAndGet
+		]
+		requestManager.runWrite [
+			while (sharedState.get == 0) {
+			}
+			sharedState.incrementAndGet
+		].join
+		assertEquals(2, sharedState.get)
+	}
+
+	@Test
+	def void testCancelWrite() {
+		requestManager.runWrite [ cancelIndicator |
+			while (!cancelIndicator.canceled) {
+			}
+			sharedState.incrementAndGet
+		]
+		requestManager.runWrite [
+			sharedState.incrementAndGet
+		].join
+		assertEquals(2, sharedState.get)
+	}
+
+	@Test
+	def void testCancelRead() {
+		sharedState.incrementAndGet
+		val future = requestManager.runRead [ cancelIndicator |
+			while (!cancelIndicator.canceled) {
+			}
+			sharedState.get
+		]
+		requestManager.runWrite [
+			sharedState.set(0)
+		].join
+		assertEquals(1, future.get)
+	}
+
+}