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 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 synchronized (lock) { 167 return booted; 168 } 169 } 170 171 // Waits until VM completes initialization 172 // 173 // This method is invoked by the Finalizer thread 174 public static void awaitBooted() throws InterruptedException { 175 synchronized (lock) { 176 while (!booted) { 177 lock.wait(); 178 } 179 } 180 } 181 182 // A user-settable upper limit on the maximum amount of allocatable direct 183 // buffer memory. This value may be changed during VM initialization if 184 // "java" is launched with "-XX:MaxDirectMemorySize=<size>". 185 // 186 // The initial value of this field is arbitrary; during JRE initialization 187 // it will be reset to the value specified on the command line, if any, 188 // otherwise to Runtime.getRuntime().maxMemory(). 189 // 190 private static long directMemory = 64 * 1024 * 1024; 191 192 // Returns the maximum amount of allocatable direct buffer memory. 193 // The directMemory variable is initialized during system initialization 194 // in the saveAndRemoveProperties method. 195 // 196 public static long maxDirectMemory() { 197 return directMemory; 198 } 199 200 // User-controllable flag that determines if direct buffers should be page 201 // aligned. The "-XX:+PageAlignDirectMemory" option can be used to force 202 // buffers, allocated by ByteBuffer.allocateDirect, to be page aligned. 203 private static boolean pageAlignDirectMemory; 204 205 // Returns {@code true} if the direct buffers should be page aligned. This 206 // variable is initialized by saveAndRemoveProperties. 207 public static boolean isDirectMemoryPageAligned() { 208 return pageAlignDirectMemory; 209 } 210 211 // A user-settable boolean to determine whether ClassLoader.loadClass should 212 // accept array syntax. This value may be changed during VM initialization 213 // via the system property "sun.lang.ClassLoader.allowArraySyntax". 214 // 215 // The default for 1.5 is "true", array syntax is allowed. In 1.6, the 216 // default will be "false". The presence of this system property to 217 // control array syntax allows applications the ability to preview this new 218 // behaviour. 219 // 220 private static boolean defaultAllowArraySyntax = false; 221 private static boolean allowArraySyntax = defaultAllowArraySyntax; 222 223 // The allowArraySyntax boolean is initialized during system initialization 224 // in the saveAndRemoveProperties method. 225 // 226 // It is initialized based on the value of the system property 227 // "sun.lang.ClassLoader.allowArraySyntax". If the system property is not 228 // provided, the default for 1.5 is "true". In 1.6, the default will be 229 // "false". If the system property is provided, then the value of 230 // allowArraySyntax will be equal to "true" if Boolean.parseBoolean() 231 // returns "true". Otherwise, the field will be set to "false". 232 // 233 public static boolean allowArraySyntax() { 234 return allowArraySyntax; 235 } 236 237 /** 238 * Returns true if the given class loader is in the system domain 239 * in which all permissions are granted. 240 */ 241 public static boolean isSystemDomainLoader(ClassLoader loader) { 242 return loader == null; 243 } 244 245 /** 246 * Returns the system property of the specified key saved at 247 * system initialization time. This method should only be used 248 * for the system properties that are not changed during runtime. 249 * It accesses a private copy of the system properties so 250 * that user's locking of the system properties object will not 251 * cause the library to deadlock. 252 * 253 * Note that the saved system properties do not include 254 * the ones set by sun.misc.Version.init(). 255 * 256 */ 257 public static String getSavedProperty(String key) { 258 if (savedProps.isEmpty()) 259 throw new IllegalStateException("Should be non-empty if initialized"); 260 261 return savedProps.getProperty(key); 262 } 263 264 // TODO: the Property Management needs to be refactored and 265 // the appropriate prop keys need to be accessible to the 266 // calling classes to avoid duplication of keys. 267 private static final Properties savedProps = new Properties(); 268 269 // Save a private copy of the system properties and remove 270 // the system properties that are not intended for public access. 271 // 272 // This method can only be invoked during system initialization. 273 public static void saveAndRemoveProperties(Properties props) { 274 if (booted) 275 throw new IllegalStateException("System initialization has completed"); 276 277 savedProps.putAll(props); 278 279 // Set the maximum amount of direct memory. This value is controlled 280 // by the vm option -XX:MaxDirectMemorySize=<size>. 281 // The maximum amount of allocatable direct buffer memory (in bytes) 282 // from the system property sun.nio.MaxDirectMemorySize set by the VM. 283 // The system property will be removed. 284 String s = (String)props.remove("sun.nio.MaxDirectMemorySize"); 285 if (s != null) { 286 if (s.equals("-1")) { 287 // -XX:MaxDirectMemorySize not given, take default 288 directMemory = Runtime.getRuntime().maxMemory(); 289 } else { 290 long l = Long.parseLong(s); 291 if (l > -1) 292 directMemory = l; 293 } 294 } 295 296 // Check if direct buffers should be page aligned 297 s = (String)props.remove("sun.nio.PageAlignDirectMemory"); 298 if ("true".equals(s)) 299 pageAlignDirectMemory = true; 300 301 // Set a boolean to determine whether ClassLoader.loadClass accepts 302 // array syntax. This value is controlled by the system property 303 // "sun.lang.ClassLoader.allowArraySyntax". 304 s = props.getProperty("sun.lang.ClassLoader.allowArraySyntax"); 305 allowArraySyntax = (s == null 306 ? defaultAllowArraySyntax 307 : Boolean.parseBoolean(s)); 308 309 // Remove other private system properties 310 // used by java.lang.Integer.IntegerCache 311 props.remove("java.lang.Integer.IntegerCache.high"); 312 313 // used by java.util.zip.ZipFile 314 props.remove("sun.zip.disableMemoryMapping"); 315 316 // used by sun.launcher.LauncherHelper 317 props.remove("sun.java.launcher.diag"); 318 } 319 320 // Initialize any miscellenous operating system settings that need to be 321 // set for the class libraries. 322 // 323 public static void initializeOSEnvironment() { 324 if (!booted) { 325 OSEnvironment.initialize(); 326 } 327 } 328 329 /* Current count of objects pending for finalization */ 330 private static volatile int finalRefCount = 0; 331 332 /* Peak count of objects pending for finalization */ 333 private static volatile int peakFinalRefCount = 0; 334 335 /* 336 * Gets the number of objects pending for finalization. 337 * 338 * @return the number of objects pending for finalization. 339 */ 340 public static int getFinalRefCount() { 341 return finalRefCount; 342 } 343 344 /* 345 * Gets the peak number of objects pending for finalization. 346 * 347 * @return the peak number of objects pending for finalization. 348 */ 349 public static int getPeakFinalRefCount() { 350 return peakFinalRefCount; 351 } 352 353 /* 354 * Add <tt>n</tt> to the objects pending for finalization count. 355 * 356 * @param n an integer value to be added to the objects pending 357 * for finalization count 358 */ 359 public static void addFinalRefCount(int n) { 360 // The caller must hold lock to synchronize the update. 361 362 finalRefCount += n; 363 if (finalRefCount > peakFinalRefCount) { 364 peakFinalRefCount = finalRefCount; 365 } 366 } 367 368 /** 369 * Returns Thread.State for the given threadStatus 370 */ 371 public static Thread.State toThreadState(int threadStatus) { 372 if ((threadStatus & JVMTI_THREAD_STATE_RUNNABLE) != 0) { 373 return RUNNABLE; 374 } else if ((threadStatus & JVMTI_THREAD_STATE_BLOCKED_ON_MONITOR_ENTER) != 0) { 375 return BLOCKED; 376 } else if ((threadStatus & JVMTI_THREAD_STATE_WAITING_INDEFINITELY) != 0) { 377 return WAITING; 378 } else if ((threadStatus & JVMTI_THREAD_STATE_WAITING_WITH_TIMEOUT) != 0) { 379 return TIMED_WAITING; 380 } else if ((threadStatus & JVMTI_THREAD_STATE_TERMINATED) != 0) { 381 return TERMINATED; 382 } else if ((threadStatus & JVMTI_THREAD_STATE_ALIVE) == 0) { 383 return NEW; 384 } else { 385 return RUNNABLE; 386 } 387 } 388 389 /* The threadStatus field is set by the VM at state transition 390 * in the hotspot implementation. Its value is set according to 391 * the JVM TI specification GetThreadState function. 392 */ 393 private final static int JVMTI_THREAD_STATE_ALIVE = 0x0001; 394 private final static int JVMTI_THREAD_STATE_TERMINATED = 0x0002; 395 private final static int JVMTI_THREAD_STATE_RUNNABLE = 0x0004; 396 private final static int JVMTI_THREAD_STATE_BLOCKED_ON_MONITOR_ENTER = 0x0400; 397 private final static int JVMTI_THREAD_STATE_WAITING_INDEFINITELY = 0x0010; 398 private final static int JVMTI_THREAD_STATE_WAITING_WITH_TIMEOUT = 0x0020; 399 400 /* 401 * Returns the first non-null class loader up the execution stack, 402 * or null if only code from the null class loader is on the stack. 403 */ 404 public static native ClassLoader latestUserDefinedLoader(); 405 406 static { 407 initialize(); 408 } 409 private native static void initialize(); 410 }