Dongwon Kang | 94eaad6 | 2018-11-27 17:02:14 -0800 | [diff] [blame] | 1 | /* |
| 2 | * Copyright (C) 2010 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 android.media; |
| 18 | |
| 19 | import android.util.Log; |
| 20 | |
| 21 | /** |
| 22 | * Note: This file is copied from dalvik.system package with the following modifications: |
| 23 | * - Remove @CorePlatformApi, @IntraCoreApi and @UnsupportedAppUsage annotations. |
| 24 | * - Replace System.logW() with android.util.Log.w(). |
| 25 | * This file should be used only within media mainline module. |
| 26 | * TODO: Remove this file and use dalvik.system.CloseGuard once |
| 27 | * @CorePlatformApi becomes stable or we have a replacement in SDK API. |
| 28 | * b/120419300 |
| 29 | * |
| 30 | * CloseGuard is a mechanism for flagging implicit finalizer cleanup of |
| 31 | * resources that should have been cleaned up by explicit close |
| 32 | * methods (aka "explicit termination methods" in Effective Java). |
| 33 | * <p> |
| 34 | * A simple example: <pre> {@code |
| 35 | * class Foo { |
| 36 | * |
| 37 | * {@literal @}ReachabilitySensitive |
| 38 | * private final CloseGuard guard = CloseGuard.get(); |
| 39 | * |
| 40 | * ... |
| 41 | * |
| 42 | * public Foo() { |
| 43 | * ...; |
| 44 | * guard.open("cleanup"); |
| 45 | * } |
| 46 | * |
| 47 | * public void cleanup() { |
| 48 | * guard.close(); |
| 49 | * ...; |
| 50 | * } |
| 51 | * |
| 52 | * protected void finalize() throws Throwable { |
| 53 | * try { |
| 54 | * // Note that guard could be null if the constructor threw. |
| 55 | * if (guard != null) { |
| 56 | * guard.warnIfOpen(); |
| 57 | * } |
| 58 | * cleanup(); |
| 59 | * } finally { |
| 60 | * super.finalize(); |
| 61 | * } |
| 62 | * } |
| 63 | * } |
| 64 | * }</pre> |
| 65 | * |
| 66 | * In usage where the resource to be explicitly cleaned up is |
| 67 | * allocated after object construction, CloseGuard protection can |
| 68 | * be deferred. For example: <pre> {@code |
| 69 | * class Bar { |
| 70 | * |
| 71 | * {@literal @}ReachabilitySensitive |
| 72 | * private final CloseGuard guard = CloseGuard.get(); |
| 73 | * |
| 74 | * ... |
| 75 | * |
| 76 | * public Bar() { |
| 77 | * ...; |
| 78 | * } |
| 79 | * |
| 80 | * public void connect() { |
| 81 | * ...; |
| 82 | * guard.open("cleanup"); |
| 83 | * } |
| 84 | * |
| 85 | * public void cleanup() { |
| 86 | * guard.close(); |
| 87 | * ...; |
| 88 | * } |
| 89 | * |
| 90 | * protected void finalize() throws Throwable { |
| 91 | * try { |
| 92 | * // Note that guard could be null if the constructor threw. |
| 93 | * if (guard != null) { |
| 94 | * guard.warnIfOpen(); |
| 95 | * } |
| 96 | * cleanup(); |
| 97 | * } finally { |
| 98 | * super.finalize(); |
| 99 | * } |
| 100 | * } |
| 101 | * } |
| 102 | * }</pre> |
| 103 | * |
| 104 | * When used in a constructor, calls to {@code open} should occur at |
| 105 | * the end of the constructor since an exception that would cause |
| 106 | * abrupt termination of the constructor will mean that the user will |
| 107 | * not have a reference to the object to cleanup explicitly. When used |
| 108 | * in a method, the call to {@code open} should occur just after |
| 109 | * resource acquisition. |
| 110 | * |
| 111 | * The @ReachabilitySensitive annotation ensures that finalize() cannot be |
| 112 | * called during the explicit call to cleanup(), prior to the guard.close call. |
| 113 | * There is an extremely small chance that, for code that neglects to call |
| 114 | * cleanup(), finalize() and thus cleanup() will be called while a method on |
| 115 | * the object is still active, but the "this" reference is no longer required. |
| 116 | * If missing cleanup() calls are expected, additional @ReachabilitySensitive |
| 117 | * annotations or reachabilityFence() calls may be required. |
| 118 | * |
| 119 | * @hide |
| 120 | */ |
| 121 | final class CloseGuard { |
| 122 | |
| 123 | /** |
| 124 | * True if collection of call-site information (the expensive operation |
| 125 | * here) and tracking via a Tracker (see below) are enabled. |
| 126 | * Enabled by default so we can diagnose issues early in VM startup. |
| 127 | * Note, however, that Android disables this early in its startup, |
| 128 | * but enables it with DropBoxing for system apps on debug builds. |
| 129 | */ |
| 130 | private static volatile boolean stackAndTrackingEnabled = true; |
| 131 | |
| 132 | /** |
| 133 | * Hook for customizing how CloseGuard issues are reported. |
| 134 | * Bypassed if stackAndTrackingEnabled was false when open was called. |
| 135 | */ |
| 136 | private static volatile Reporter reporter = new DefaultReporter(); |
| 137 | |
| 138 | /** |
| 139 | * Hook for customizing how CloseGuard issues are tracked. |
| 140 | */ |
| 141 | private static volatile Tracker currentTracker = null; // Disabled by default. |
| 142 | |
| 143 | /** |
| 144 | * Returns a CloseGuard instance. {@code #open(String)} can be used to set |
| 145 | * up the instance to warn on failure to close. |
| 146 | */ |
| 147 | public static CloseGuard get() { |
| 148 | return new CloseGuard(); |
| 149 | } |
| 150 | |
| 151 | /** |
| 152 | * Enables/disables stack capture and tracking. A call stack is captured |
| 153 | * during open(), and open/close events are reported to the Tracker, only |
| 154 | * if enabled is true. If a stack trace was captured, the {@link |
| 155 | * #getReporter() reporter} is informed of unclosed resources; otherwise a |
| 156 | * one-line warning is logged. |
| 157 | */ |
| 158 | public static void setEnabled(boolean enabled) { |
| 159 | CloseGuard.stackAndTrackingEnabled = enabled; |
| 160 | } |
| 161 | |
| 162 | /** |
| 163 | * True if CloseGuard stack capture and tracking are enabled. |
| 164 | */ |
| 165 | public static boolean isEnabled() { |
| 166 | return stackAndTrackingEnabled; |
| 167 | } |
| 168 | |
| 169 | /** |
| 170 | * Used to replace default Reporter used to warn of CloseGuard |
| 171 | * violations when stack tracking is enabled. Must be non-null. |
| 172 | */ |
| 173 | public static void setReporter(Reporter rep) { |
| 174 | if (rep == null) { |
| 175 | throw new NullPointerException("reporter == null"); |
| 176 | } |
| 177 | CloseGuard.reporter = rep; |
| 178 | } |
| 179 | |
| 180 | /** |
| 181 | * Returns non-null CloseGuard.Reporter. |
| 182 | */ |
| 183 | public static Reporter getReporter() { |
| 184 | return reporter; |
| 185 | } |
| 186 | |
| 187 | /** |
| 188 | * Sets the {@link Tracker} that is notified when resources are allocated and released. |
| 189 | * The Tracker is invoked only if CloseGuard {@link #isEnabled()} held when {@link #open()} |
| 190 | * was called. A null argument disables tracking. |
| 191 | * |
| 192 | * <p>This is only intended for use by {@code dalvik.system.CloseGuardSupport} class and so |
| 193 | * MUST NOT be used for any other purposes. |
| 194 | */ |
| 195 | public static void setTracker(Tracker tracker) { |
| 196 | currentTracker = tracker; |
| 197 | } |
| 198 | |
| 199 | /** |
| 200 | * Returns {@link #setTracker(Tracker) last Tracker that was set}, or null to indicate |
| 201 | * there is none. |
| 202 | * |
| 203 | * <p>This is only intended for use by {@code dalvik.system.CloseGuardSupport} class and so |
| 204 | * MUST NOT be used for any other purposes. |
| 205 | */ |
| 206 | public static Tracker getTracker() { |
| 207 | return currentTracker; |
| 208 | } |
| 209 | |
| 210 | private CloseGuard() {} |
| 211 | |
| 212 | /** |
| 213 | * {@code open} initializes the instance with a warning that the caller |
| 214 | * should have explicitly called the {@code closer} method instead of |
| 215 | * relying on finalization. |
| 216 | * |
| 217 | * @param closer non-null name of explicit termination method. Printed by warnIfOpen. |
| 218 | * @throws NullPointerException if closer is null. |
| 219 | */ |
| 220 | public void open(String closer) { |
| 221 | // always perform the check for valid API usage... |
| 222 | if (closer == null) { |
| 223 | throw new NullPointerException("closer == null"); |
| 224 | } |
| 225 | // ...but avoid allocating an allocation stack if "disabled" |
| 226 | if (!stackAndTrackingEnabled) { |
| 227 | closerNameOrAllocationInfo = closer; |
| 228 | return; |
| 229 | } |
| 230 | String message = "Explicit termination method '" + closer + "' not called"; |
| 231 | Throwable stack = new Throwable(message); |
| 232 | closerNameOrAllocationInfo = stack; |
| 233 | Tracker tracker = currentTracker; |
| 234 | if (tracker != null) { |
| 235 | tracker.open(stack); |
| 236 | } |
| 237 | } |
| 238 | |
| 239 | // We keep either an allocation stack containing the closer String or, when |
| 240 | // in disabled state, just the closer String. |
| 241 | // We keep them in a single field only to minimize overhead. |
| 242 | private Object /* String or Throwable */ closerNameOrAllocationInfo; |
| 243 | |
| 244 | /** |
| 245 | * Marks this CloseGuard instance as closed to avoid warnings on |
| 246 | * finalization. |
| 247 | */ |
| 248 | public void close() { |
| 249 | Tracker tracker = currentTracker; |
| 250 | if (tracker != null && closerNameOrAllocationInfo instanceof Throwable) { |
| 251 | // Invoke tracker on close only if we invoked it on open. Tracker may have changed. |
| 252 | tracker.close((Throwable) closerNameOrAllocationInfo); |
| 253 | } |
| 254 | closerNameOrAllocationInfo = null; |
| 255 | } |
| 256 | |
| 257 | /** |
| 258 | * Logs a warning if the caller did not properly cleanup by calling an |
| 259 | * explicit close method before finalization. If CloseGuard was enabled |
| 260 | * when the CloseGuard was created, passes the stacktrace associated with |
| 261 | * the allocation to the current reporter. If it was not enabled, it just |
| 262 | * directly logs a brief message. |
| 263 | */ |
| 264 | public void warnIfOpen() { |
| 265 | if (closerNameOrAllocationInfo != null) { |
| 266 | if (closerNameOrAllocationInfo instanceof String) { |
| 267 | Log.w("CloseGuard", "A resource failed to call " |
| 268 | + (String) closerNameOrAllocationInfo + ". "); |
| 269 | } else { |
| 270 | String message = |
| 271 | "A resource was acquired at attached stack trace but never released. "; |
| 272 | message += "See java.io.Closeable for information on avoiding resource leaks."; |
| 273 | Throwable stack = (Throwable) closerNameOrAllocationInfo; |
| 274 | reporter.report(message, stack); |
| 275 | } |
| 276 | } |
| 277 | } |
| 278 | |
| 279 | /** |
| 280 | * Interface to allow customization of tracking behaviour. |
| 281 | * |
| 282 | * <p>This is only intended for use by {@code dalvik.system.CloseGuardSupport} class and so |
| 283 | * MUST NOT be used for any other purposes. |
| 284 | */ |
| 285 | public interface Tracker { |
| 286 | void open(Throwable allocationSite); |
| 287 | void close(Throwable allocationSite); |
| 288 | } |
| 289 | |
| 290 | /** |
| 291 | * Interface to allow customization of reporting behavior. |
| 292 | * @hide |
| 293 | */ |
| 294 | public interface Reporter { |
| 295 | void report(String message, Throwable allocationSite); |
| 296 | } |
| 297 | |
| 298 | /** |
| 299 | * Default Reporter which reports CloseGuard violations to the log. |
| 300 | */ |
| 301 | private static final class DefaultReporter implements Reporter { |
| 302 | private DefaultReporter() {} |
| 303 | |
| 304 | @Override public void report (String message, Throwable allocationSite) { |
| 305 | Log.w("CloseGuard", message, allocationSite); |
| 306 | } |
| 307 | } |
| 308 | } |