/*******************************************************************************

 * Copyright (c) 2009 IBM Corporation 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

 *

 * Contributors:

 *     IBM Corporation - initial API and implementation

 ******************************************************************************/

package org.eclipse.ui.tests.concurrency;

import junit.framework.TestCase;

import org.eclipse.core.runtime.SubMonitor;

import org.eclipse.core.runtime.jobs.ISchedulingRule;

import org.eclipse.core.runtime.jobs.Job;

import org.eclipse.swt.SWTException;

import org.eclipse.swt.widgets.Display;

/**

 * This tests the simple traditional deadlock of a thread holding a scheduling rule trying

 * to perform a syncExec, while the UI thread is waiting for that scheduling rule.

 * UISynchronizer and UILockListener conspire to prevent deadlock in this case.

 * See https://bugs.eclipse.org/bugs/show_bug.cgi?id=296056.

 */

public class SyncExecWhileUIThreadWaitsForRuleTest extends TestCase {

	class TestRule implements ISchedulingRule {

		public boolean contains(ISchedulingRule rule) {

			return rule == this;

		}

		public boolean isConflicting(ISchedulingRule rule) {

			return rule == this;

		}

	}

	public void testDeadlock() {

		final ISchedulingRule rule = new TestRule();

		final boolean[] blocked = new boolean[] {false};

		final boolean[] lockAcquired = new boolean[] {false};

		final SubMonitor beginRuleMonitor = SubMonitor.convert(null);

		Thread locking = new Thread("SyncExecWhileUIThreadWaitsForRuleTest") {

			public void run() {

				try {

					//first make sure this background thread owns the lock

					Job.getJobManager().beginRule(rule, null);

					//spawn an asyncExec that will cause the UI thread to be blocked

					Display.getDefault().asyncExec(new Runnable() {

						public void run() {

							blocked[0] = true;

							Job.getJobManager().beginRule(rule, beginRuleMonitor);

							Job.getJobManager().endRule(rule);

							blocked[0] = false;

						}

					});

					//wait until the UI thread is blocked waiting for the lock

					while (!blocked[0]) {

						try {

							Thread.sleep(100);

						} catch (InterruptedException e) {

							e.printStackTrace();

						}

					}

					//now attempt to do a syncExec that also acquires the lock

					//this should succeed even while the above asyncExec is blocked, thanks to UISynchronizer

					Display.getDefault().syncExec(new Runnable() {

						public void run() {

							//use a timeout to avoid deadlock in case of regression

							Job.getJobManager().beginRule(rule, null);

							lockAcquired[0] = true;

							Job.getJobManager().endRule(rule);

						}

					});

				} finally {

					Job.getJobManager().endRule(rule);

				}

			}

		};

		locking.start();

		//create a thread that will cancel the monitor after 60 seconds so we don't hang the tests

		final long waitStart = System.currentTimeMillis();

		Thread canceler = new Thread("Canceler") {

			public void run() {

				while (true) {

					if (System.currentTimeMillis() - waitStart > 60000) {

						beginRuleMonitor.setCanceled(true);

						break;

					}

				}

			}

		};

		canceler.start();

		//wait until we succeeded to acquire the lock in the UI thread

		Display display = Display.getDefault();

		while (!lockAcquired[0]) {

			//spin event loop so that asyncExed above gets run

			try {

				if (!display.readAndDispatch())

					display.sleep();

			} catch (SWTException e) {

				fail("Deadlock occurred");

			}

		}

		//if the monitor was canceled then we got a deadlock

		assertFalse("deadlock occurred", beginRuleMonitor.isCanceled());

	}

}