1 /* 2 * Copyright (c) 1996, 2014, Oracle and/or its affiliates. All rights reserved. 3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. 4 * 5 * This code is free software; you can redistribute it and/or modify it 6 * under the terms of the GNU General Public License version 2 only, as 7 * published by the Free Software Foundation. Oracle designates this 8 * particular file as subject to the "Classpath" exception as provided 9 * by Oracle in the LICENSE file that accompanied this code. 10 * 11 * This code is distributed in the hope that it will be useful, but WITHOUT 12 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or 13 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License 14 * version 2 for more details (a copy is included in the LICENSE file that 15 * accompanied this code). 16 * 17 * You should have received a copy of the GNU General Public License version 18 * 2 along with this work; if not, write to the Free Software Foundation, 19 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. 20 * 21 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA 22 * or visit www.oracle.com if you need additional information or have any 23 * questions. 24 */ 25 26 package sun.misc; 27 28 import static java.lang.Thread.State.*; 29 import java.util.Properties; 30 import java.util.HashMap; 31 import java.util.Map; 32 import java.util.Set; 33 34 public class VM { 35 36 /* The following methods used to be native methods that instruct 37 * the VM to selectively suspend certain threads in low-memory 38 * situations. They are inherently dangerous and not implementable 39 * on native threads. We removed them in JDK 1.2. The skeletons 40 * remain so that existing applications that use these methods 41 * will still work. 42 */ 43 private static boolean suspended = false; 44 45 /** @deprecated */ 46 @Deprecated 47 public static boolean threadsSuspended() { 48 return suspended; 49 } 50 51 @SuppressWarnings("deprecation") 52 public static boolean allowThreadSuspension(ThreadGroup g, boolean b) { 53 return g.allowThreadSuspension(b); 54 } 55 56 /** @deprecated */ 57 @Deprecated 58 public static boolean suspendThreads() { 59 suspended = true; 60 return true; 61 } 62 63 // Causes any suspended threadgroups to be resumed. 64 /** @deprecated */ 65 @Deprecated 66 public static void unsuspendThreads() { 67 suspended = false; 68 } 69 70 // Causes threadgroups no longer marked suspendable to be resumed. 71 /** @deprecated */ 72 @Deprecated 73 public static void unsuspendSomeThreads() { 74 } 75 76 /* Deprecated fields and methods -- Memory advice not supported in 1.2 */ 77 78 /** @deprecated */ 79 @Deprecated 80 public static final int STATE_GREEN = 1; 81 82 /** @deprecated */ 83 @Deprecated 84 public static final int STATE_YELLOW = 2; 85 86 /** @deprecated */ 87 @Deprecated 88 public static final int STATE_RED = 3; 89 90 /** @deprecated */ 91 @Deprecated 92 public static final int getState() { 93 return STATE_GREEN; 94 } 95 96 /** @deprecated */ 97 @Deprecated 98 public static void registerVMNotification(VMNotification n) { } 99 100 /** @deprecated */ 101 @Deprecated 102 public static void asChange(int as_old, int as_new) { } 103 104 /** @deprecated */ 105 @Deprecated 106 public static void asChange_otherthread(int as_old, int as_new) { } 107 108 /* 109 * Not supported in 1.2 because these will have to be exported as 110 * JVM functions, and we are not sure we want do that. Leaving 111 * here so it can be easily resurrected -- just remove the // 112 * comments. 113 */ 114 115 /** 116 * Resume Java profiling. All profiling data is added to any 117 * earlier profiling, unless <code>resetJavaProfiler</code> is 118 * called in between. If profiling was not started from the 119 * command line, <code>resumeJavaProfiler</code> will start it. 120 * <p> 121 * 122 * NOTE: Profiling must be enabled from the command line for a 123 * java.prof report to be automatically generated on exit; if not, 124 * writeJavaProfilerReport must be invoked to write a report. 125 * 126 * @see resetJavaProfiler 127 * @see writeJavaProfilerReport 128 */ 129 130 // public native static void resumeJavaProfiler(); 131 132 /** 133 * Suspend Java profiling. 134 */ 135 // public native static void suspendJavaProfiler(); 136 137 /** 138 * Initialize Java profiling. Any accumulated profiling 139 * information is discarded. 140 */ 141 // public native static void resetJavaProfiler(); 142 143 /** 144 * Write the current profiling contents to the file "java.prof". 145 * If the file already exists, it will be overwritten. 146 */ 147 // public native static void writeJavaProfilerReport(); 148 149 150 private static volatile boolean booted = false; 151 private static final Object lock = new Object(); 152 153 // Invoked by by System.initializeSystemClass just before returning. 154 // Subsystems that are invoked during initialization can check this 155 // property in order to avoid doing things that should wait until the 156 // application class loader has been set up. 157 // 158 public static void booted() { 159 synchronized (lock) { 160 booted = true; 161 lock.notifyAll(); 162 } 163 } 164 165 public static boolean isBooted() { 166 return booted; 167 } 168 169 // Waits until VM completes initialization 170 // 171 // This method is invoked by the Finalizer thread 172 public static void awaitBooted() throws InterruptedException { 173 synchronized (lock) { 174 while (!booted) { 175 lock.wait(); 176 } 177 } 178 } 179 180 // A user-settable upper limit on the maximum amount of allocatable direct 181 // buffer memory. This value may be changed during VM initialization if 182 // "java" is launched with "-XX:MaxDirectMemorySize=<size>". 183 // 184 // The initial value of this field is arbitrary; during JRE initialization 185 // it will be reset to the value specified on the command line, if any, 186 // otherwise to Runtime.getRuntime().maxMemory(). 187 // 188 private static long directMemory = 64 * 1024 * 1024; 189 190 // Returns the maximum amount of allocatable direct buffer memory. 191 // The directMemory variable is initialized during system initialization 192 // in the saveAndRemoveProperties method. 193 // 194 public static long maxDirectMemory() { 195 return directMemory; 196 } 197 198 // User-controllable flag that determines if direct buffers should be page 199 // aligned. The "-XX:+PageAlignDirectMemory" option can be used to force 200 // buffers, allocated by ByteBuffer.allocateDirect, to be page aligned. 201 private static boolean pageAlignDirectMemory; 202 203 // Returns {@code true} if the direct buffers should be page aligned. This 204 // variable is initialized by saveAndRemoveProperties. 205 public static boolean isDirectMemoryPageAligned() { 206 return pageAlignDirectMemory; 207 } 208 209 // A user-settable boolean to determine whether ClassLoader.loadClass should 210 // accept array syntax. This value may be changed during VM initialization 211 // via the system property "sun.lang.ClassLoader.allowArraySyntax". 212 // 213 // The default for 1.5 is "true", array syntax is allowed. In 1.6, the 214 // default will be "false". The presence of this system property to 215 // control array syntax allows applications the ability to preview this new 216 // behaviour. 217 // 218 private static boolean defaultAllowArraySyntax = false; 219 private static boolean allowArraySyntax = defaultAllowArraySyntax; 220 221 // The allowArraySyntax boolean is initialized during system initialization 222 // in the saveAndRemoveProperties method. 223 // 224 // It is initialized based on the value of the system property 225 // "sun.lang.ClassLoader.allowArraySyntax". If the system property is not 226 // provided, the default for 1.5 is "true". In 1.6, the default will be 227 // "false". If the system property is provided, then the value of 228 // allowArraySyntax will be equal to "true" if Boolean.parseBoolean() 229 // returns "true". Otherwise, the field will be set to "false". 230 // 231 public static boolean allowArraySyntax() { 232 return allowArraySyntax; 233 } 234 235 /** 236 * Returns true if the given class loader is in the system domain 237 * in which all permissions are granted. 238 */ 239 public static boolean isSystemDomainLoader(ClassLoader loader) { 240 return loader == null; 241 } 242 243 /** 244 * Returns the system property of the specified key saved at 245 * system initialization time. This method should only be used 246 * for the system properties that are not changed during runtime. 247 * It accesses a private copy of the system properties so 248 * that user's locking of the system properties object will not 249 * cause the library to deadlock. 250 * 251 * Note that the saved system properties do not include 252 * the ones set by sun.misc.Version.init(). 253 * 254 */ 255 public static String getSavedProperty(String key) { 256 if (savedProps.isEmpty()) 257 throw new IllegalStateException("Should be non-empty if initialized"); 258 259 return savedProps.getProperty(key); 260 } 261 262 // TODO: the Property Management needs to be refactored and 263 // the appropriate prop keys need to be accessible to the 264 // calling classes to avoid duplication of keys. 265 private static final Properties savedProps = new Properties(); 266 267 // Save a private copy of the system properties and remove 268 // the system properties that are not intended for public access. 269 // 270 // This method can only be invoked during system initialization. 271 public static void saveAndRemoveProperties(Properties props) { 272 if (booted) 273 throw new IllegalStateException("System initialization has completed"); 274 275 savedProps.putAll(props); 276 277 // Set the maximum amount of direct memory. This value is controlled 278 // by the vm option -XX:MaxDirectMemorySize=<size>. 279 // The maximum amount of allocatable direct buffer memory (in bytes) 280 // from the system property sun.nio.MaxDirectMemorySize set by the VM. 281 // The system property will be removed. 282 String s = (String)props.remove("sun.nio.MaxDirectMemorySize"); 283 if (s != null) { 284 if (s.equals("-1")) { 285 // -XX:MaxDirectMemorySize not given, take default 286 directMemory = Runtime.getRuntime().maxMemory(); 287 } else { 288 long l = Long.parseLong(s); 289 if (l > -1) 290 directMemory = l; 291 } 292 } 293 294 // Check if direct buffers should be page aligned 295 s = (String)props.remove("sun.nio.PageAlignDirectMemory"); 296 if ("true".equals(s)) 297 pageAlignDirectMemory = true; 298 299 // Set a boolean to determine whether ClassLoader.loadClass accepts 300 // array syntax. This value is controlled by the system property 301 // "sun.lang.ClassLoader.allowArraySyntax". 302 s = props.getProperty("sun.lang.ClassLoader.allowArraySyntax"); 303 allowArraySyntax = (s == null 304 ? defaultAllowArraySyntax 305 : Boolean.parseBoolean(s)); 306 307 // Remove other private system properties 308 // used by java.lang.Integer.IntegerCache 309 props.remove("java.lang.Integer.IntegerCache.high"); 310 311 // used by java.util.zip.ZipFile 312 props.remove("sun.zip.disableMemoryMapping"); 313 314 // used by sun.launcher.LauncherHelper 315 props.remove("sun.java.launcher.diag"); 316 317 // used by sun.misc.URLClassPath 318 props.remove("sun.cds.enableSharedLookupCache"); 319 } 320 321 // Initialize any miscellenous operating system settings that need to be 322 // set for the class libraries. 323 // 324 public static void initializeOSEnvironment() { 325 if (!booted) { 326 OSEnvironment.initialize(); 327 } 328 } 329 330 /* Current count of objects pending for finalization */ 331 private static volatile int finalRefCount = 0; 332 333 /* Peak count of objects pending for finalization */ 334 private static volatile int peakFinalRefCount = 0; 335 336 /* 337 * Gets the number of objects pending for finalization. 338 * 339 * @return the number of objects pending for finalization. 340 */ 341 public static int getFinalRefCount() { 342 return finalRefCount; 343 } 344 345 /* 346 * Gets the peak number of objects pending for finalization. 347 * 348 * @return the peak number of objects pending for finalization. 349 */ 350 public static int getPeakFinalRefCount() { 351 return peakFinalRefCount; 352 } 353 354 /* 355 * Add <tt>n</tt> to the objects pending for finalization count. 356 * 357 * @param n an integer value to be added to the objects pending 358 * for finalization count 359 */ 360 public static void addFinalRefCount(int n) { 361 // The caller must hold lock to synchronize the update. 362 363 finalRefCount += n; 364 if (finalRefCount > peakFinalRefCount) { 365 peakFinalRefCount = finalRefCount; 366 } 367 } 368 369 /** 370 * Returns Thread.State for the given threadStatus 371 */ 372 public static Thread.State toThreadState(int threadStatus) { 373 if ((threadStatus & JVMTI_THREAD_STATE_RUNNABLE) != 0) { 374 return RUNNABLE; 375 } else if ((threadStatus & JVMTI_THREAD_STATE_BLOCKED_ON_MONITOR_ENTER) != 0) { 376 return BLOCKED; 377 } else if ((threadStatus & JVMTI_THREAD_STATE_WAITING_INDEFINITELY) != 0) { 378 return WAITING; 379 } else if ((threadStatus & JVMTI_THREAD_STATE_WAITING_WITH_TIMEOUT) != 0) { 380 return TIMED_WAITING; 381 } else if ((threadStatus & JVMTI_THREAD_STATE_TERMINATED) != 0) { 382 return TERMINATED; 383 } else if ((threadStatus & JVMTI_THREAD_STATE_ALIVE) == 0) { 384 return NEW; 385 } else { 386 return RUNNABLE; 387 } 388 } 389 390 /* The threadStatus field is set by the VM at state transition 391 * in the hotspot implementation. Its value is set according to 392 * the JVM TI specification GetThreadState function. 393 */ 394 private final static int JVMTI_THREAD_STATE_ALIVE = 0x0001; 395 private final static int JVMTI_THREAD_STATE_TERMINATED = 0x0002; 396 private final static int JVMTI_THREAD_STATE_RUNNABLE = 0x0004; 397 private final static int JVMTI_THREAD_STATE_BLOCKED_ON_MONITOR_ENTER = 0x0400; 398 private final static int JVMTI_THREAD_STATE_WAITING_INDEFINITELY = 0x0010; 399 private final static int JVMTI_THREAD_STATE_WAITING_WITH_TIMEOUT = 0x0020; 400 401 /* 402 * Returns the first non-null class loader up the execution stack, 403 * or null if only code from the null class loader is on the stack. 404 */ 405 public static native ClassLoader latestUserDefinedLoader(); 406 407 static { 408 initialize(); 409 } 410 private native static void initialize(); 411 }