1 /* 2 * Copyright (C) 2021 The Android Open Source Project 3 * 4 * Licensed under the Apache License, Version 2.0 (the "License"); 5 * you may not use this file except in compliance with the License. 6 * You may obtain a copy of the License at 7 * 8 * http://www.apache.org/licenses/LICENSE-2.0 9 * 10 * Unless required by applicable law or agreed to in writing, software 11 * distributed under the License is distributed on an "AS IS" BASIS, 12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 13 * See the License for the specific language governing permissions and 14 * limitations under the License. 15 */ 16 17 package com.android.internal.annotations; 18 19 import static java.lang.annotation.ElementType.FIELD; 20 21 import java.lang.annotation.Retention; 22 import java.lang.annotation.RetentionPolicy; 23 import java.lang.annotation.Target; 24 25 /** 26 * Specifies a list of locks which are required for read/write operations on a data field. 27 * 28 * <p> 29 * To annotate methods accessing the data field with the annotation {@link CompositeRWLock}, 30 * use {@link GuardedBy#value} to annotate method w/ write and/or read access to the data field, 31 * use {@link GuardedBy#anyOf} to annotate method w/ read only access to the data field. 32 * </p> 33 * 34 * <p> 35 * When its {@link #value()} consists of multiple locks: 36 * <ul> 37 * <li>To write to the protected data, acquire <b>all</b> of the locks 38 * in the order of the appearance in the {@link #value}.</li> 39 * <li>To read from the protected data, acquire any of the locks in the {@link #value}.</li> 40 * </ul> 41 * </p> 42 */ 43 @Target({FIELD}) 44 @Retention(RetentionPolicy.CLASS) 45 public @interface CompositeRWLock { value()46 String[] value() default {}; 47 } 48