/**
Copyright (C) SYSTAP, LLC DBA Blazegraph 2006-2016. All rights reserved.
Contact:
SYSTAP, LLC DBA Blazegraph
2501 Calvert ST NW #106
Washington, DC 20008
licenses@blazegraph.com
This program is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; version 2 of the License.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program; if not, write to the Free Software
Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
*/
package com.bigdata.util.concurrent;
import java.util.Iterator;
import java.util.Map;
import java.util.concurrent.Callable;
import java.util.concurrent.ConcurrentHashMap;
import java.util.concurrent.atomic.AtomicInteger;
import java.util.concurrent.locks.Condition;
import org.apache.log4j.Logger;
/**
* Pattern used to guard critical regions that await {@link Condition}s when a
* concurrent event may cause the {@link Condition} to become unsatisfiable.
*
* @author <a href="mailto:thompsonbry@users.sourceforge.net">Bryan Thompson</a>
*/
public class ThreadGuard {
private static final transient Logger log = Logger.getLogger(ThreadGuard.class);
public static abstract class Guard {
abstract public void run() throws InterruptedException;
}
/**
* Execute a critical region which needs to be interrupted if some condition
* is violated.
*
* @param r
* The lambda.
*/
public void guard(final Runnable r) {
incThread();
try {
r.run();
} finally {
decThread();
}
}
/**
* Execute a critical region which needs to be interrupted if some condition
* is violated.
*
* @param r
* The lambda.
*
* @return The result (if any).
*/
public void guard(final Guard r) throws InterruptedException {
incThread();
try {
r.run();
} catch(InterruptedException e) {
throw e;
} catch (Exception e) {
throw new RuntimeException(e);
} finally {
decThread();
}
}
/**
* Execute a critical region which needs to be interrupted if some condition
* is violated.
*
* @param r
* The lambda.
*
* @return The result (if any).
* @throws Exception
*/
public <T> T guard(final Callable<T> r) throws Exception {
incThread();
try {
return r.call();
} finally {
decThread();
}
}
private final ConcurrentHashMap<Thread, AtomicInteger> threads = new ConcurrentHashMap<Thread, AtomicInteger>();
/**
* Increment thread in critical region awaiting a {@link Condition}.
*/
private void incThread() {
synchronized (threads) {
final Thread t = Thread.currentThread();
final AtomicInteger tmp = threads.get(t);
if (tmp == null) {
threads.put(t, new AtomicInteger(1));
} else {
tmp.incrementAndGet();
}
}
}
/**
* Decrement thread in critical region awaiting a {@link Condition}.
*/
public void decThread() {
synchronized (threads) {
final Thread t = Thread.currentThread();
final AtomicInteger tmp = threads.get(t);
if (tmp == null) {
// code must be wrong with broken try/finally.
throw new AssertionError();
}
if (tmp.decrementAndGet() == 0) {
threads.remove(t);
}
}
}
/**
* Interrupt any threads in critical regions awaiting a
* {@link Condition}.
*/
public void interruptAll() {
synchronized (threads) {
final Iterator<Map.Entry<Thread, AtomicInteger>> itr = threads
.entrySet().iterator();
while(itr.hasNext()) {
final Map.Entry<Thread,AtomicInteger> e = itr.next();
final Thread t = e.getKey();
final int counter = e.getValue().get();
t.interrupt();
log.warn("Interrupted: " + t.getName() + "@counter=" + counter);
}
// Note: Will be cleared when we leave the finally{}.
// // clear everything!
// threads.clear();
}
}
}