Author: pderop
Date: Fri Oct 25 18:38:24 2013
New Revision: 1535805
URL: http://svn.apache.org/r1535805
Log:
FELIX-3910: Added new SerialExecutor, which blocks other invokers while a
leader is executing a task.
The executor is reentrant: when one leader executing thread reschedule some
runnables, the tasks are executed directly
in the leader caller thread.
Added:
felix/trunk/dependencymanager/core/src/main/java/org/apache/felix/dm/impl/BlockingSerialExecutor.java
Added:
felix/trunk/dependencymanager/core/src/main/java/org/apache/felix/dm/impl/BlockingSerialExecutor.java
URL:
http://svn.apache.org/viewvc/felix/trunk/dependencymanager/core/src/main/java/org/apache/felix/dm/impl/BlockingSerialExecutor.java?rev=1535805&view=auto
==============================================================================
---
felix/trunk/dependencymanager/core/src/main/java/org/apache/felix/dm/impl/BlockingSerialExecutor.java
(added)
+++
felix/trunk/dependencymanager/core/src/main/java/org/apache/felix/dm/impl/BlockingSerialExecutor.java
Fri Oct 25 18:38:24 2013
@@ -0,0 +1,71 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements. See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership. The ASF licenses this file
+ * to you 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.apache.felix.dm.impl;
+
+import java.util.LinkedList;
+
+/**
+ * This class allows to serialize the execution of tasks on one single/unique
thread.
+ * Other threads are blocked until they are elected for execution.
+ *
+ * <p>note I: when one leader thread executes a task, it does not hold any
locks
+ * while executing the task, and does not execute tasks scheduled by other
threads.
+ *
+ * <p>note II: this executor is reentrant: when one task executed by a leader
thread
+ * reschedule another task, then the task is run immediately.
+ *
+ * @author <a href="mailto:[email protected]";>Felix Project Team</a>
+ */
+public class BlockingSerialExecutor {
+ private final LinkedList m_tasksQueue = new LinkedList();
+ private Thread m_executingThread = null;
+
+ /**
+ * Executes a task exclusively without holding any locks (other concurrent
tasks are blocked until the current task is executed).
+ * @param task a task to be executed serially, without holding any locks.
+ */
+ public void execute(Runnable task) {
+ boolean releaseLock = false;
+ synchronized (this) {
+ if (m_executingThread != Thread.currentThread()) {
+ m_tasksQueue.addLast(task);
+ while (m_tasksQueue.size() > 0 && m_tasksQueue.get(0) != task)
{
+ try {
+ // TODO it might make sense to use a maxwait time and
throw an exception on timeouts.
+ wait();
+ } catch (InterruptedException e) {
+ }
+ }
+ m_executingThread = Thread.currentThread();
+ releaseLock = true;
+ }
+ }
+ try {
+ task.run();
+ } finally {
+ if (releaseLock) {
+ synchronized (this) {
+ m_tasksQueue.remove(task);
+ notifyAll();
+ m_executingThread = null;
+ }
+ }
+ }
+ }
+}
