1 /* 2 * Copyright (c) 1996, 2012, 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 boolean awaitBooted() throws InterruptedException { 173 synchronized (lock) { 174 while (!booted) { 175 lock.wait(); 176 } 177 } 178 return booted; 179 } 180 181 // A user-settable upper limit on the maximum amount of allocatable direct 182 // buffer memory. This value may be changed during VM initialization if 183 // "java" is launched with "-XX:MaxDirectMemorySize=<size>". 184 // 185 // The initial value of this field is arbitrary; during JRE initialization 186 // it will be reset to the value specified on the command line, if any, 187 // otherwise to Runtime.getRuntime().maxMemory(). 188 // 189 private static long directMemory = 64 * 1024 * 1024; 190 191 // Returns the maximum amount of allocatable direct buffer memory. 192 // The directMemory variable is initialized during system initialization 193 // in the saveAndRemoveProperties method. 194 // 195 public static long maxDirectMemory() { 196 return directMemory; 197 } 198 199 // User-controllable flag that determines if direct buffers should be page 200 // aligned. The "-XX:+PageAlignDirectMemory" option can be used to force 201 // buffers, allocated by ByteBuffer.allocateDirect, to be page aligned. 202 private static boolean pageAlignDirectMemory; 203 204 // Returns {@code true} if the direct buffers should be page aligned. This 205 // variable is initialized by saveAndRemoveProperties. 206 public static boolean isDirectMemoryPageAligned() { 207 return pageAlignDirectMemory; 208 } 209 210 // A user-settable boolean to determine whether ClassLoader.loadClass should 211 // accept array syntax. This value may be changed during VM initialization 212 // via the system property "sun.lang.ClassLoader.allowArraySyntax". 213 // 214 // The default for 1.5 is "true", array syntax is allowed. In 1.6, the 215 // default will be "false". The presence of this system property to 216 // control array syntax allows applications the ability to preview this new 217 // behaviour. 218 // 219 private static boolean defaultAllowArraySyntax = false; 220 private static boolean allowArraySyntax = defaultAllowArraySyntax; 221 222 // The allowArraySyntax boolean is initialized during system initialization 223 // in the saveAndRemoveProperties method. 224 // 225 // It is initialized based on the value of the system property 226 // "sun.lang.ClassLoader.allowArraySyntax". If the system property is not 227 // provided, the default for 1.5 is "true". In 1.6, the default will be 228 // "false". If the system property is provided, then the value of 229 // allowArraySyntax will be equal to "true" if Boolean.parseBoolean() 230 // returns "true". Otherwise, the field will be set to "false". 231 // 232 public static boolean allowArraySyntax() { 233 return allowArraySyntax; 234 } 235 236 /** 237 * Returns true if the given class loader is in the system domain 238 * in which all permissions are granted. 239 */ 240 public static boolean isSystemDomainLoader(ClassLoader loader) { 241 return loader == null; 242 } 243 244 /** 245 * Returns the system property of the specified key saved at 246 * system initialization time. This method should only be used 247 * for the system properties that are not changed during runtime. 248 * It accesses a private copy of the system properties so 249 * that user's locking of the system properties object will not 250 * cause the library to deadlock. 251 * 252 * Note that the saved system properties do not include 253 * the ones set by sun.misc.Version.init(). 254 * 255 */ 256 public static String getSavedProperty(String key) { 257 if (savedProps.isEmpty()) 258 throw new IllegalStateException("Should be non-empty if initialized"); 259 260 return savedProps.getProperty(key); 261 } 262 263 // TODO: the Property Management needs to be refactored and 264 // the appropriate prop keys need to be accessible to the 265 // calling classes to avoid duplication of keys. 266 private static final Properties savedProps = new Properties(); 267 268 // Save a private copy of the system properties and remove 269 // the system properties that are not intended for public access. 270 // 271 // This method can only be invoked during system initialization. 272 public static void saveAndRemoveProperties(Properties props) { 273 if (booted) 274 throw new IllegalStateException("System initialization has completed"); 275 276 savedProps.putAll(props); 277 278 // Set the maximum amount of direct memory. This value is controlled 279 // by the vm option -XX:MaxDirectMemorySize=<size>. 280 // The maximum amount of allocatable direct buffer memory (in bytes) 281 // from the system property sun.nio.MaxDirectMemorySize set by the VM. 282 // The system property will be removed. 283 String s = (String)props.remove("sun.nio.MaxDirectMemorySize"); 284 if (s != null) { 285 if (s.equals("-1")) { 286 // -XX:MaxDirectMemorySize not given, take default 287 directMemory = Runtime.getRuntime().maxMemory(); 288 } else { 289 long l = Long.parseLong(s); 290 if (l > -1) 291 directMemory = l; 292 } 293 } 294 295 // Check if direct buffers should be page aligned 296 s = (String)props.remove("sun.nio.PageAlignDirectMemory"); 297 if ("true".equals(s)) 298 pageAlignDirectMemory = true; 299 300 // Set a boolean to determine whether ClassLoader.loadClass accepts 301 // array syntax. This value is controlled by the system property 302 // "sun.lang.ClassLoader.allowArraySyntax". 303 s = props.getProperty("sun.lang.ClassLoader.allowArraySyntax"); 304 allowArraySyntax = (s == null 305 ? defaultAllowArraySyntax 306 : Boolean.parseBoolean(s)); 307 308 // Remove other private system properties 309 // used by java.lang.Integer.IntegerCache 310 props.remove("java.lang.Integer.IntegerCache.high"); 311 312 // used by java.util.zip.ZipFile 313 props.remove("sun.zip.disableMemoryMapping"); 314 315 // used by sun.launcher.LauncherHelper 316 props.remove("sun.java.launcher.diag"); 317 } 318 319 // Initialize any miscellenous operating system settings that need to be 320 // set for the class libraries. 321 // 322 public static void initializeOSEnvironment() { 323 if (!booted) { 324 OSEnvironment.initialize(); 325 } 326 } 327 328 /* Current count of objects pending for finalization */ 329 private static volatile int finalRefCount = 0; 330 331 /* Peak count of objects pending for finalization */ 332 private static volatile int peakFinalRefCount = 0; 333 334 /* 335 * Gets the number of objects pending for finalization. 336 * 337 * @return the number of objects pending for finalization. 338 */ 339 public static int getFinalRefCount() { 340 return finalRefCount; 341 } 342 343 /* 344 * Gets the peak number of objects pending for finalization. 345 * 346 * @return the peak number of objects pending for finalization. 347 */ 348 public static int getPeakFinalRefCount() { 349 return peakFinalRefCount; 350 } 351 352 /* 353 * Add <tt>n</tt> to the objects pending for finalization count. 354 * 355 * @param n an integer value to be added to the objects pending 356 * for finalization count 357 */ 358 public static void addFinalRefCount(int n) { 359 // The caller must hold lock to synchronize the update. 360 361 finalRefCount += n; 362 if (finalRefCount > peakFinalRefCount) { 363 peakFinalRefCount = finalRefCount; 364 } 365 } 366 367 /** 368 * Returns Thread.State for the given threadStatus 369 */ 370 public static Thread.State toThreadState(int threadStatus) { 371 if ((threadStatus & JVMTI_THREAD_STATE_RUNNABLE) != 0) { 372 return RUNNABLE; 373 } else if ((threadStatus & JVMTI_THREAD_STATE_BLOCKED_ON_MONITOR_ENTER) != 0) { 374 return BLOCKED; 375 } else if ((threadStatus & JVMTI_THREAD_STATE_WAITING_INDEFINITELY) != 0) { 376 return WAITING; 377 } else if ((threadStatus & JVMTI_THREAD_STATE_WAITING_WITH_TIMEOUT) != 0) { 378 return TIMED_WAITING; 379 } else if ((threadStatus & JVMTI_THREAD_STATE_TERMINATED) != 0) { 380 return TERMINATED; 381 } else if ((threadStatus & JVMTI_THREAD_STATE_ALIVE) == 0) { 382 return NEW; 383 } else { 384 return RUNNABLE; 385 } 386 } 387 388 /* The threadStatus field is set by the VM at state transition 389 * in the hotspot implementation. Its value is set according to 390 * the JVM TI specification GetThreadState function. 391 */ 392 private final static int JVMTI_THREAD_STATE_ALIVE = 0x0001; 393 private final static int JVMTI_THREAD_STATE_TERMINATED = 0x0002; 394 private final static int JVMTI_THREAD_STATE_RUNNABLE = 0x0004; 395 private final static int JVMTI_THREAD_STATE_BLOCKED_ON_MONITOR_ENTER = 0x0400; 396 private final static int JVMTI_THREAD_STATE_WAITING_INDEFINITELY = 0x0010; 397 private final static int JVMTI_THREAD_STATE_WAITING_WITH_TIMEOUT = 0x0020; 398 399 /* 400 * Returns the first non-null class loader up the execution stack, 401 * or null if only code from the null class loader is on the stack. 402 */ 403 public static native ClassLoader latestUserDefinedLoader(); 404 405 static { 406 initialize(); 407 } 408 private native static void initialize(); 409 }