| /* |
| * 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.ignite.internal.util; |
| |
| import org.apache.ignite.internal.util.tostring.*; |
| |
| import java.util.concurrent.locks.*; |
| |
| /** |
| * Synchronization aid to track "busy" state of a subsystem that owns it. |
| * <p> |
| * For example, there may be a manager that have different threads for some |
| * purposes and the manager must not be stopped while at least a single thread |
| * is in "busy" state. In this situation each thread must enter to "busy" |
| * state calling method {@link #enterBusy()} in critical pieces of code |
| * which, i.e. use grid kernal functionality, notifying that the manager |
| * and the whole grid kernal cannot be stopped while it's in progress. Once |
| * the activity is done, the thread should leave "busy" state calling method |
| * {@link #leaveBusy()}. The manager itself, when stopping, should call method |
| * {@link #block} that blocks till all activities leave "busy" state. |
| */ |
| @GridToStringExclude |
| public class GridBusyLock { |
| /** Underlying re-entrant read-write lock. */ |
| @SuppressWarnings("TypeMayBeWeakened") |
| private final ReentrantReadWriteLock lock = new ReentrantReadWriteLock(); |
| |
| /** |
| * Enters "busy" state. |
| * |
| * @return {@code true} if entered to busy state. |
| */ |
| public boolean enterBusy() { |
| return !lock.writeLock().isHeldByCurrentThread() && lock.readLock().tryLock(); |
| } |
| |
| /** |
| * Checks if busy lock was blocked by current thread. |
| * |
| * @return {@code True} if busy lock was blocked by current thread. |
| */ |
| public boolean blockedByCurrentThread() { |
| return lock.writeLock().isHeldByCurrentThread(); |
| } |
| |
| /** |
| * Leaves "busy" state. |
| */ |
| public void leaveBusy() { |
| lock.readLock().unlock(); |
| } |
| |
| /** |
| * Blocks current thread till all activities left "busy" state |
| * and prevents them from further entering to "busy" state. |
| */ |
| @SuppressWarnings({"LockAcquiredButNotSafelyReleased"}) |
| public void block() { |
| lock.writeLock().lock(); |
| } |
| |
| /** |
| * Makes possible for activities entering busy state again. |
| */ |
| public void unblock() { |
| lock.writeLock().unlock(); |
| } |
| } |