mirror of git://gcc.gnu.org/git/gcc.git
462 lines
15 KiB
Java
462 lines
15 KiB
Java
/* VMThread -- VM interface for Thread of executable code
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Copyright (C) 2003, 2004, 2005, 2006 Free Software Foundation
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This file is part of GNU Classpath.
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GNU Classpath is free software; you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation; either version 2, or (at your option)
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any later version.
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GNU Classpath is distributed in the hope that it will be useful, but
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WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with GNU Classpath; see the file COPYING. If not, write to the
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Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
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02110-1301 USA.
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Linking this library statically or dynamically with other modules is
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making a combined work based on this library. Thus, the terms and
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conditions of the GNU General Public License cover the whole
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combination.
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As a special exception, the copyright holders of this library give you
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permission to link this library with independent modules to produce an
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executable, regardless of the license terms of these independent
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modules, and to copy and distribute the resulting executable under
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terms of your choice, provided that you also meet, for each linked
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independent module, the terms and conditions of the license of that
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module. An independent module is a module which is not derived from
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or based on this library. If you modify this library, you may extend
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this exception to your version of the library, but you are not
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obligated to do so. If you do not wish to do so, delete this
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exception statement from your version. */
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package java.lang;
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/**
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* VM interface for Thread of executable code. Holds VM dependent state.
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* It is deliberately package local and final and should only be accessed
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* by the Thread class.
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* <p>
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* This is the GNU Classpath reference implementation, it should be adapted
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* for a specific VM.
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* <p>
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* The following methods must be implemented:
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* <ul>
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* <li>native void start(long stacksize);
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* <li>native void interrupt();
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* <li>native boolean isInterrupted();
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* <li>native void suspend();
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* <li>native void resume();
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* <li>native void nativeSetPriority(int priority);
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* <li>native void nativeStop(Throwable t);
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* <li>native static Thread currentThread();
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* <li>static native void yield();
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* <li>static native boolean interrupted();
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* </ul>
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* All other methods may be implemented to make Thread handling more efficient
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* or to implement some optional (and sometimes deprecated) behaviour. Default
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* implementations are provided but it is highly recommended to optimize them
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* for a specific VM.
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*
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* @author Jeroen Frijters (jeroen@frijters.net)
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* @author Dalibor Topic (robilad@kaffe.org)
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*/
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final class VMThread
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{
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/**
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* The Thread object that this VM state belongs to.
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* Used in currentThread() and start().
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* Note: when this thread dies, this reference is *not* cleared
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*/
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volatile Thread thread;
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/**
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* Flag that is set when the thread runs, used by stop() to protect against
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* stop's getting lost.
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*/
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private volatile boolean running;
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/**
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* VM private data.
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*/
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private transient Object vmdata;
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/**
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* Private constructor, create VMThreads with the static create method.
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*
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* @param thread The Thread object that was just created.
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*/
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private VMThread(Thread thread)
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{
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this.thread = thread;
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}
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/**
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* This method is the initial Java code that gets executed when a native
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* thread starts. It's job is to coordinate with the rest of the VMThread
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* logic and to start executing user code and afterwards handle clean up.
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*/
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private void run()
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{
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try
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{
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try
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{
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running = true;
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synchronized(thread)
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{
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Throwable t = thread.stillborn;
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if(t != null)
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{
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thread.stillborn = null;
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throw t;
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}
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}
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thread.run();
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}
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catch(Throwable t)
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{
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try
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{
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Thread.UncaughtExceptionHandler handler;
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handler = thread.getUncaughtExceptionHandler();
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handler.uncaughtException(thread, t);
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}
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catch(Throwable ignore)
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{
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}
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}
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}
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finally
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{
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// Setting runnable to false is partial protection against stop
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// being called while we're cleaning up. To be safe all code in
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// VMThread be unstoppable.
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running = false;
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thread.die();
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synchronized(this)
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{
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// release the threads waiting to join us
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notifyAll();
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}
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}
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}
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/**
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* Creates a native Thread. This is called from the start method of Thread.
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* The Thread is started.
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*
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* @param thread The newly created Thread object
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* @param stacksize Indicates the requested stacksize. Normally zero,
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* non-zero values indicate requested stack size in bytes but it is up
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* to the specific VM implementation to interpret them and may be ignored.
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*/
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static void create(Thread thread, long stacksize)
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{
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VMThread vmThread = new VMThread(thread);
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vmThread.start(stacksize);
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thread.vmThread = vmThread;
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}
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/**
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* Gets the name of the thread. Usually this is the name field of the
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* associated Thread object, but some implementation might choose to
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* return the name of the underlying platform thread.
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*/
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String getName()
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{
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return thread.name;
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}
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/**
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* Set the name of the thread. Usually this sets the name field of the
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* associated Thread object, but some implementations might choose to
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* set the name of the underlying platform thread.
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* @param name The new name
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*/
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void setName(String name)
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{
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thread.name = name;
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}
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/**
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* Set the thread priority field in the associated Thread object and
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* calls the native method to set the priority of the underlying
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* platform thread.
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* @param priority The new priority
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*/
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void setPriority(int priority)
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{
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thread.priority = priority;
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nativeSetPriority(priority);
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}
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/**
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* Returns the priority. Usually this is the priority field from the
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* associated Thread object, but some implementation might choose to
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* return the priority of the underlying platform thread.
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* @return this Thread's priority
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*/
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int getPriority()
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{
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return thread.priority;
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}
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/**
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* Returns true if the thread is a daemon thread. Usually this is the
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* daemon field from the associated Thread object, but some
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* implementation might choose to return the daemon state of the underlying
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* platform thread.
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* @return whether this is a daemon Thread or not
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*/
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boolean isDaemon()
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{
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return thread.daemon;
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}
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/**
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* Returns the number of stack frames in this Thread.
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* Will only be called when when a previous call to suspend() returned true.
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*
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* @deprecated unsafe operation
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*/
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native int countStackFrames();
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/**
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* Wait the specified amount of time for the Thread in question to die.
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*
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* <p>Note that 1,000,000 nanoseconds == 1 millisecond, but most VMs do
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* not offer that fine a grain of timing resolution. Besides, there is
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* no guarantee that this thread can start up immediately when time expires,
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* because some other thread may be active. So don't expect real-time
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* performance.
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*
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* @param ms the number of milliseconds to wait, or 0 for forever
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* @param ns the number of extra nanoseconds to sleep (0-999999)
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* @throws InterruptedException if the Thread is interrupted; it's
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* <i>interrupted status</i> will be cleared
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*/
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synchronized void join(long ms, int ns) throws InterruptedException
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{
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// Round up
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ms += (ns != 0) ? 1 : 0;
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// Compute end time, but don't overflow
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long now = System.currentTimeMillis();
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long end = now + ms;
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if (end < now)
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end = Long.MAX_VALUE;
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// A VM is allowed to return from wait() without notify() having been
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// called, so we loop to handle possible spurious wakeups.
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while(thread.vmThread != null)
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{
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// We use the VMThread object to wait on, because this is a private
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// object, so client code cannot call notify on us.
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wait(ms);
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if(ms != 0)
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{
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now = System.currentTimeMillis();
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ms = end - now;
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if(ms <= 0)
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{
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break;
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}
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}
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}
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}
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/**
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* Cause this Thread to stop abnormally and throw the specified exception.
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* If you stop a Thread that has not yet started, the stop is ignored
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* (contrary to what the JDK documentation says).
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* <b>WARNING</b>This bypasses Java security, and can throw a checked
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* exception which the call stack is unprepared to handle. Do not abuse
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* this power.
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*
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* <p>This is inherently unsafe, as it can interrupt synchronized blocks and
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* leave data in bad states.
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*
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* <p><b>NOTE</b> stop() should take care not to stop a thread if it is
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* executing code in this class.
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*
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* @param t the Throwable to throw when the Thread dies
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* @deprecated unsafe operation, try not to use
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*/
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void stop(Throwable t)
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{
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// Note: we assume that we own the lock on thread
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// (i.e. that Thread.stop() is synchronized)
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if(running)
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nativeStop(t);
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else
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thread.stillborn = t;
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}
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/**
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* Create a native thread on the underlying platform and start it executing
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* on the run method of this object.
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* @param stacksize the requested size of the native thread stack
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*/
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native void start(long stacksize);
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/**
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* Interrupt this thread.
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*/
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native void interrupt();
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/**
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* Determine whether this Thread has been interrupted, but leave
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* the <i>interrupted status</i> alone in the process.
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*
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* @return whether the Thread has been interrupted
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*/
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native boolean isInterrupted();
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/**
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* Suspend this Thread. It will not come back, ever, unless it is resumed.
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*/
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native void suspend();
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/**
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* Resume this Thread. If the thread is not suspended, this method does
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* nothing.
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*/
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native void resume();
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/**
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* Set the priority of the underlying platform thread.
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*
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* @param priority the new priority
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*/
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native void nativeSetPriority(int priority);
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/**
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* Asynchronously throw the specified throwable in this Thread.
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*
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* @param t the exception to throw
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*/
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native void nativeStop(Throwable t);
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/**
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* Return the Thread object associated with the currently executing
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* thread.
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*
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* @return the currently executing Thread
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*/
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static native Thread currentThread();
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/**
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* Yield to another thread. The Thread will not lose any locks it holds
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* during this time. There are no guarantees which thread will be
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* next to run, and it could even be this one, but most VMs will choose
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* the highest priority thread that has been waiting longest.
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*/
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static native void yield();
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/**
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* Suspend the current Thread's execution for the specified amount of
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* time. The Thread will not lose any locks it has during this time. There
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* are no guarantees which thread will be next to run, but most VMs will
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* choose the highest priority thread that has been waiting longest.
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*
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* <p>Note that 1,000,000 nanoseconds == 1 millisecond, but most VMs do
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* not offer that fine a grain of timing resolution. Besides, there is
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* no guarantee that this thread can start up immediately when time expires,
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* because some other thread may be active. So don't expect real-time
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* performance.
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*
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* @param ms the number of milliseconds to sleep.
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* @param ns the number of extra nanoseconds to sleep (0-999999)
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* @throws InterruptedException if the Thread is (or was) interrupted;
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* it's <i>interrupted status</i> will be cleared
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*/
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static void sleep(long ms, int ns) throws InterruptedException
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{
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// Note: JDK treats a zero length sleep is like Thread.yield(),
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// without checking the interrupted status of the thread.
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// It's unclear if this is a bug in the implementation or the spec.
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// See http://bugs.sun.com/bugdatabase/view_bug.do?bug_id=6213203
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if (ms == 0 && ns == 0)
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{
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if (Thread.interrupted())
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throw new InterruptedException();
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return;
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}
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// Compute end time, but don't overflow
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long now = System.currentTimeMillis();
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long end = now + ms;
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if (end < now)
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end = Long.MAX_VALUE;
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// A VM is allowed to return from wait() without notify() having been
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// called, so we loop to handle possible spurious wakeups.
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VMThread vt = Thread.currentThread().vmThread;
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synchronized (vt)
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{
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while (true)
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{
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vt.wait(ms, ns);
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now = System.currentTimeMillis();
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if (now >= end)
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break;
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ms = end - now;
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ns = 0;
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}
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}
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}
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/**
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* Determine whether the current Thread has been interrupted, and clear
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* the <i>interrupted status</i> in the process.
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*
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* @return whether the current Thread has been interrupted
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*/
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static native boolean interrupted();
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/**
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* Checks whether the current thread holds the monitor on a given object.
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* This allows you to do <code>assert Thread.holdsLock(obj)</code>.
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*
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* @param obj the object to check
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* @return true if the current thread is currently synchronized on obj
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* @throws NullPointerException if obj is null
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*/
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static boolean holdsLock(Object obj)
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{
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/* Use obj.notify to check if the current thread holds
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* the monitor of the object.
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* If it doesn't, notify will throw an exception.
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*/
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try
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{
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obj.notify();
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// okay, current thread holds lock
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return true;
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}
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catch (IllegalMonitorStateException e)
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{
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// it doesn't hold the lock
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return false;
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}
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}
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/**
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* Returns the current state of the thread.
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* The value must be one of "BLOCKED", "NEW",
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* "RUNNABLE", "TERMINATED", "TIMED_WAITING" or
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* "WAITING".
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*
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* @return a string corresponding to one of the
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* thread enumeration states specified above.
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*/
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native String getState();
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}
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