sonatype-lift[bot] commented on code in PR #2018: URL: https://github.com/apache/zookeeper/pull/2018#discussion_r1236642403
########## zookeeper-server/src/main/java/org/apache/zookeeper/common/BatchedArrayBlockingQueue.java: ########## @@ -0,0 +1,405 @@ +/* + * + * 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.zookeeper.common; + +import java.util.*; +import java.util.concurrent.BlockingQueue; +import java.util.concurrent.TimeUnit; +import java.util.concurrent.locks.Condition; +import java.util.concurrent.locks.ReentrantLock; + +/** + * This implements a {@link BlockingQueue} backed by an array with fixed capacity. + * + * <p>This queue only allows 1 consumer thread to dequeue items and multiple producer threads. + */ +public class BatchedArrayBlockingQueue<T> + extends AbstractQueue<T> + implements BlockingQueue<T>, BatchedBlockingQueue<T> { + + private final ReentrantLock lock = new ReentrantLock(); + + private final Condition notEmpty = lock.newCondition(); + private final Condition notFull = lock.newCondition(); + + private final int capacity; + private final T[] data; + + private int size; + + private int consumerIdx; + private int producerIdx; + + @SuppressWarnings("unchecked") + public BatchedArrayBlockingQueue(int capacity) { + this.capacity = capacity; + this.data = (T[]) new Object[this.capacity]; + } + + private T dequeueOne() { + T item = data[consumerIdx]; + data[consumerIdx] = null; + if (++consumerIdx == capacity) { + consumerIdx = 0; + } + + if (size-- == capacity) { + notFull.signalAll(); + } + + return item; + } + + private void enqueueOne(T item) { + data[producerIdx] = item; + if (++producerIdx == capacity) { + producerIdx = 0; + } + + if (size++ == 0) { + notEmpty.signalAll(); + } + } + + @Override + public T poll() { + lock.lock(); + + try { + if (size == 0) { + return null; + } + + return dequeueOne(); + } finally { + lock.unlock(); + } + } + + @Override + public T peek() { + lock.lock(); + + try { + if (size == 0) { + return null; + } + + return data[consumerIdx]; + } finally { + lock.unlock(); + } + } + + @Override + public boolean offer(T e) { + lock.lock(); + + try { + if (size == capacity) { + return false; + } + + enqueueOne(e); + + return true; + } finally { + lock.unlock(); + } + } + + @Override + public void put(T e) throws InterruptedException { + lock.lockInterruptibly(); + + try { + while (size == capacity) { + notFull.await(); + } + + enqueueOne(e); + } finally { + lock.unlock(); + } + } + + public int putAll(List<T> c) throws InterruptedException { + lock.lockInterruptibly(); + + try { + while (size == capacity) { + notFull.await(); + } + + int availableCapacity = capacity - size; + + int toInsert = Math.min(availableCapacity, c.size()); + + int producerIdx = this.producerIdx; + for (int i = 0; i < toInsert; i++) { + data[producerIdx] = c.get(i); + if (++producerIdx == capacity) { + producerIdx = 0; + } + } + + this.producerIdx = producerIdx; + + if (size == 0) { + notEmpty.signalAll(); + } + + size += toInsert; + + return toInsert; + } finally { + lock.unlock(); + } + } + + @Override + public void putAll(T[] a, int offset, int len) throws InterruptedException { + while (len > 0) { + int published = internalPutAll(a, offset, len); + offset += published; + len -= published; + } + } + + private int internalPutAll(T[] a, int offset, int len) throws InterruptedException { + lock.lockInterruptibly(); + + try { + while (size == capacity) { + notFull.await(); + } + + int availableCapacity = capacity - size; + int toInsert = Math.min(availableCapacity, len); + int producerIdx = this.producerIdx; + + // First span + int firstSpan = Math.min(toInsert, capacity - producerIdx); + System.arraycopy(a, offset, data, producerIdx, firstSpan); + producerIdx += firstSpan; + + int secondSpan = toInsert - firstSpan; + if (secondSpan > 0) { + System.arraycopy(a, offset + firstSpan, data, 0, secondSpan); + producerIdx = secondSpan; + } + + if (producerIdx == capacity) { + producerIdx = 0; + } + + this.producerIdx = producerIdx; + + if (size == 0) { + notEmpty.signalAll(); + } + + size += toInsert; + return toInsert; + } finally { + lock.unlock(); + } + } + + @Override + public boolean offer(T e, long timeout, TimeUnit unit) throws InterruptedException { + long remainingTimeNanos = unit.toNanos(timeout); + + lock.lockInterruptibly(); + try { + while (size == capacity) { + if (remainingTimeNanos <= 0L) { + return false; + } + + remainingTimeNanos = notFull.awaitNanos(remainingTimeNanos); + } + + enqueueOne(e); + return true; + } finally { + lock.unlock(); + } + } + + @Override + public T take() throws InterruptedException { + lock.lockInterruptibly(); + + try { + while (size == 0) { + notEmpty.await(); + } + + return dequeueOne(); + } finally { + lock.unlock(); + } + } + + @Override + public T poll(long timeout, TimeUnit unit) throws InterruptedException { + long remainingTimeNanos = unit.toNanos(timeout); + + lock.lockInterruptibly(); + try { + while (size == 0) { + if (remainingTimeNanos <= 0L) { + return null; + } + + remainingTimeNanos = notEmpty.awaitNanos(remainingTimeNanos); + } + + return dequeueOne(); + } finally { + lock.unlock(); + } + } + + @Override + public int remainingCapacity() { + return capacity - size; Review Comment: <picture><img alt="7% of developers fix this issue" src="https://lift.sonatype.com/api/commentimage/fixrate/7/display.svg";></picture> <b>*THREAD_SAFETY_VIOLATION:</b>* Read/Write race. Non-private method `BatchedArrayBlockingQueue.remainingCapacity()` reads without synchronization from `this.size`. Potentially races with write in method `BatchedArrayBlockingQueue.clear()`. Reporting because another access to the same memory occurs on a background thread, although this access may not. --- <details><summary>ℹ️ Expand to see all <b>@sonatype-lift</b> commands</summary> You can reply with the following commands. 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