1 /*
   2  * Copyright (c) 1996, 2011, 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 
 152     // Invoked by by System.initializeSystemClass just before returning.
 153     // Subsystems that are invoked during initialization can check this
 154     // property in order to avoid doing things that should wait until the
 155     // application class loader has been set up.
 156     //
 157     public static void booted() {
 158         booted = true;
 159     }
 160 
 161     public static boolean isBooted() {
 162         return booted;
 163     }
 164 
 165     // A user-settable upper limit on the maximum amount of allocatable direct
 166     // buffer memory.  This value may be changed during VM initialization if
 167     // "java" is launched with "-XX:MaxDirectMemorySize=<size>".
 168     //
 169     // The initial value of this field is arbitrary; during JRE initialization
 170     // it will be reset to the value specified on the command line, if any,
 171     // otherwise to Runtime.getRuntime().maxMemory().
 172     //
 173     private static long directMemory = 64 * 1024 * 1024;
 174 
 175     // Returns the maximum amount of allocatable direct buffer memory.
 176     // The directMemory variable is initialized during system initialization
 177     // in the saveAndRemoveProperties method.
 178     //
 179     public static long maxDirectMemory() {
 180         return directMemory;
 181     }
 182 
 183     // User-controllable flag that determines if direct buffers should be page
 184     // aligned. The "-XX:+PageAlignDirectMemory" option can be used to force
 185     // buffers, allocated by ByteBuffer.allocateDirect, to be page aligned.
 186     private static boolean pageAlignDirectMemory;
 187 
 188     // Returns {@code true} if the direct buffers should be page aligned. This
 189     // variable is initialized by saveAndRemoveProperties.
 190     public static boolean isDirectMemoryPageAligned() {
 191         return pageAlignDirectMemory;
 192     }
 193 
 194     // A user-settable boolean to determine whether ClassLoader.loadClass should
 195     // accept array syntax.  This value may be changed during VM initialization
 196     // via the system property "sun.lang.ClassLoader.allowArraySyntax".
 197     //
 198     // The default for 1.5 is "true", array syntax is allowed.  In 1.6, the
 199     // default will be "false".  The presence of this system property to
 200     // control array syntax allows applications the ability to preview this new
 201     // behaviour.
 202     //
 203     private static boolean defaultAllowArraySyntax = false;
 204     private static boolean allowArraySyntax = defaultAllowArraySyntax;
 205 
 206     // The allowArraySyntax boolean is initialized during system initialization
 207     // in the saveAndRemoveProperties method.
 208     //
 209     // It is initialized based on the value of the system property
 210     // "sun.lang.ClassLoader.allowArraySyntax".  If the system property is not
 211     // provided, the default for 1.5 is "true".  In 1.6, the default will be
 212     // "false".  If the system property is provided, then the value of
 213     // allowArraySyntax will be equal to "true" if Boolean.parseBoolean()
 214     // returns "true".   Otherwise, the field will be set to "false".
 215     //
 216     public static boolean allowArraySyntax() {
 217         return allowArraySyntax;
 218     }
 219 
 220     /**
 221      * Returns the system property of the specified key saved at
 222      * system initialization time.  This method should only be used
 223      * for the system properties that are not changed during runtime.
 224      * It accesses a private copy of the system properties so
 225      * that user's locking of the system properties object will not
 226      * cause the library to deadlock.
 227      *
 228      * Note that the saved system properties do not include
 229      * the ones set by sun.misc.Version.init().
 230      *
 231      */
 232     public static String getSavedProperty(String key) {
 233         if (savedProps.isEmpty())
 234             throw new IllegalStateException("Should be non-empty if initialized");
 235 
 236         return savedProps.getProperty(key);
 237     }
 238 
 239     // TODO: the Property Management needs to be refactored and
 240     // the appropriate prop keys need to be accessible to the
 241     // calling classes to avoid duplication of keys.
 242     private static final Properties savedProps = new Properties();
 243 
 244     // Save a private copy of the system properties and remove
 245     // the system properties that are not intended for public access.
 246     //
 247     // This method can only be invoked during system initialization.
 248     public static void saveAndRemoveProperties(Properties props) {
 249         if (booted)
 250             throw new IllegalStateException("System initialization has completed");
 251 
 252         savedProps.putAll(props);
 253 
 254         // Set the maximum amount of direct memory.  This value is controlled
 255         // by the vm option -XX:MaxDirectMemorySize=<size>.
 256         // The maximum amount of allocatable direct buffer memory (in bytes)
 257         // from the system property sun.nio.MaxDirectMemorySize set by the VM.
 258         // The system property will be removed.
 259         String s = (String)props.remove("sun.nio.MaxDirectMemorySize");
 260         if (s != null) {
 261             if (s.equals("-1")) {
 262                 // -XX:MaxDirectMemorySize not given, take default
 263                 directMemory = Runtime.getRuntime().maxMemory();
 264             } else {
 265                 long l = Long.parseLong(s);
 266                 if (l > -1)
 267                     directMemory = l;
 268             }
 269         }
 270 
 271         // Check if direct buffers should be page aligned
 272         s = (String)props.remove("sun.nio.PageAlignDirectMemory");
 273         if ("true".equals(s))
 274             pageAlignDirectMemory = true;
 275 
 276         // Set a boolean to determine whether ClassLoader.loadClass accepts
 277         // array syntax.  This value is controlled by the system property
 278         // "sun.lang.ClassLoader.allowArraySyntax".
 279         s = props.getProperty("sun.lang.ClassLoader.allowArraySyntax");
 280         allowArraySyntax = (s == null
 281                                ? defaultAllowArraySyntax
 282                                : Boolean.parseBoolean(s));
 283 
 284         // Remove other private system properties
 285         // used by java.lang.Integer.IntegerCache
 286         props.remove("java.lang.Integer.IntegerCache.high");
 287 
 288         // used by java.util.zip.ZipFile
 289         props.remove("sun.zip.disableMemoryMapping");
 290 
 291         // used by sun.launcher.LauncherHelper
 292         props.remove("sun.java.launcher.diag");
 293     }
 294 
 295     // Initialize any miscellenous operating system settings that need to be
 296     // set for the class libraries.
 297     //
 298     public static void initializeOSEnvironment() {
 299         if (!booted) {
 300             OSEnvironment.initialize();
 301         }
 302     }
 303 
 304     /* Current count of objects pending for finalization */
 305     private static volatile int finalRefCount = 0;
 306 
 307     /* Peak count of objects pending for finalization */
 308     private static volatile int peakFinalRefCount = 0;
 309 
 310     /*
 311      * Gets the number of objects pending for finalization.
 312      *
 313      * @return the number of objects pending for finalization.
 314      */
 315     public static int getFinalRefCount() {
 316         return finalRefCount;
 317     }
 318 
 319     /*
 320      * Gets the peak number of objects pending for finalization.
 321      *
 322      * @return the peak number of objects pending for finalization.
 323      */
 324     public static int getPeakFinalRefCount() {
 325         return peakFinalRefCount;
 326     }
 327 
 328     /*
 329      * Add <tt>n</tt> to the objects pending for finalization count.
 330      *
 331      * @param n an integer value to be added to the objects pending
 332      * for finalization count
 333      */
 334     public static void addFinalRefCount(int n) {
 335         // The caller must hold lock to synchronize the update.
 336 
 337         finalRefCount += n;
 338         if (finalRefCount > peakFinalRefCount) {
 339             peakFinalRefCount = finalRefCount;
 340         }
 341     }
 342 
 343     /**
 344      * Returns Thread.State for the given threadStatus
 345      */
 346     public static Thread.State toThreadState(int threadStatus) {
 347         if ((threadStatus & JVMTI_THREAD_STATE_RUNNABLE) != 0) {
 348             return RUNNABLE;
 349         } else if ((threadStatus & JVMTI_THREAD_STATE_BLOCKED_ON_MONITOR_ENTER) != 0) {
 350             return BLOCKED;
 351         } else if ((threadStatus & JVMTI_THREAD_STATE_WAITING_INDEFINITELY) != 0) {
 352             return WAITING;
 353         } else if ((threadStatus & JVMTI_THREAD_STATE_WAITING_WITH_TIMEOUT) != 0) {
 354             return TIMED_WAITING;
 355         } else if ((threadStatus & JVMTI_THREAD_STATE_TERMINATED) != 0) {
 356             return TERMINATED;
 357         } else if ((threadStatus & JVMTI_THREAD_STATE_ALIVE) == 0) {
 358             return NEW;
 359         } else {
 360             return RUNNABLE;
 361         }
 362     }
 363 
 364     /* The threadStatus field is set by the VM at state transition
 365      * in the hotspot implementation. Its value is set according to
 366      * the JVM TI specification GetThreadState function.
 367      */
 368     private final static int JVMTI_THREAD_STATE_ALIVE = 0x0001;
 369     private final static int JVMTI_THREAD_STATE_TERMINATED = 0x0002;
 370     private final static int JVMTI_THREAD_STATE_RUNNABLE = 0x0004;
 371     private final static int JVMTI_THREAD_STATE_BLOCKED_ON_MONITOR_ENTER = 0x0400;
 372     private final static int JVMTI_THREAD_STATE_WAITING_INDEFINITELY = 0x0010;
 373     private final static int JVMTI_THREAD_STATE_WAITING_WITH_TIMEOUT = 0x0020;
 374 
 375     /*
 376      * Returns the first non-null class loader up the execution stack,
 377      * or null if only code from the null class loader is on the stack.
 378      */
 379     public static native ClassLoader latestUserDefinedLoader();
 380 
 381     static {
 382         initialize();
 383     }
 384     private native static void initialize();
 385 }