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/*
* Copyright (c) 1994, 2021, Oracle and/or its affiliates. All rights reserved.
* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
*
* This code is free software; you can redistribute it and/or modify it
* under the terms of the GNU General Public License version 2 only, as
* published by the Free Software Foundation. Oracle designates this
* particular file as subject to the "Classpath" exception as provided
* by Oracle in the LICENSE file that accompanied this code.
*
* This code is distributed in the hope that it will be useful, but WITHOUT
* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
* version 2 for more details (a copy is included in the LICENSE file that
* accompanied this code).
*
* You should have received a copy of the GNU General Public License version
* 2 along with this work; if not, write to the Free Software Foundation,
* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
*
* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
* or visit www.oracle.com if you need additional information or have any
* questions.
*/
package java.lang;
import java.lang.ref.Reference;
import java.lang.ref.ReferenceQueue;
import java.lang.ref.WeakReference;
import java.security.AccessController;
import java.security.AccessControlContext;
import java.security.PrivilegedAction;
import java.util.Map;
import java.util.HashMap;
import java.util.concurrent.ConcurrentHashMap;
import java.util.concurrent.ConcurrentMap;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.locks.LockSupport;
import jdk.internal.misc.TerminatingThreadLocal;
import jdk.internal.reflect.CallerSensitive;
import jdk.internal.reflect.Reflection;
import jdk.internal.vm.annotation.IntrinsicCandidate;
import sun.nio.ch.Interruptible;
import sun.security.util.SecurityConstants;
/**
* A thread is a thread of execution in a program. The Java
* Virtual Machine allows an application to have multiple threads of
* execution running concurrently.
*
* Every thread has a priority. Threads with higher priority are
* executed in preference to threads with lower priority. Each thread
* may or may not also be marked as a daemon. When code running in
* some thread creates a new {@code Thread} object, the new
* thread has its priority initially set equal to the priority of the
* creating thread, and is a daemon thread if and only if the
* creating thread is a daemon.
*
* When a Java Virtual Machine starts up, there is usually a single
* non-daemon thread (which typically calls the method named
* {@code main} of some designated class). The Java Virtual
* Machine continues to execute threads until either of the following
* occurs:
*
* - The {@code exit} method of class {@code Runtime} has been
* called and the security manager has permitted the exit operation
* to take place.
*
- All threads that are not daemon threads have died, either by
* returning from the call to the {@code run} method or by
* throwing an exception that propagates beyond the {@code run}
* method.
*
*
* There are two ways to create a new thread of execution. One is to
* declare a class to be a subclass of {@code Thread}. This
* subclass should override the {@code run} method of class
* {@code Thread}. An instance of the subclass can then be
* allocated and started. For example, a thread that computes primes
* larger than a stated value could be written as follows:
*
* class PrimeThread extends Thread {
* long minPrime;
* PrimeThread(long minPrime) {
* this.minPrime = minPrime;
* }
*
* public void run() {
* // compute primes larger than minPrime
* . . .
* }
* }
*
*
* The following code would then create a thread and start it running:
*
* PrimeThread p = new PrimeThread(143);
* p.start();
*
*
* The other way to create a thread is to declare a class that
* implements the {@code Runnable} interface. That class then
* implements the {@code run} method. An instance of the class can
* then be allocated, passed as an argument when creating
* {@code Thread}, and started. The same example in this other
* style looks like the following:
*
* class PrimeRun implements Runnable {
* long minPrime;
* PrimeRun(long minPrime) {
* this.minPrime = minPrime;
* }
*
* public void run() {
* // compute primes larger than minPrime
* . . .
* }
* }
*
*
* The following code would then create a thread and start it running:
*
* PrimeRun p = new PrimeRun(143);
* new Thread(p).start();
*
*
* Every thread has a name for identification purposes. More than
* one thread may have the same name. If a name is not specified when
* a thread is created, a new name is generated for it.
*
* Unless otherwise noted, passing a {@code null} argument to a constructor
* or method in this class will cause a {@link NullPointerException} to be
* thrown.
*
* @see Runnable
* @see Runtime#exit(int)
* @see #run()
* @see #stop()
* @since 1.0
*/
public class Thread implements Runnable {
/* Make sure registerNatives is the first thing does. */
private static native void registerNatives();
static {
registerNatives();
}
private volatile String name;
private int priority;
/* Whether or not the thread is a daemon thread. */
private boolean daemon = false;
/* Interrupt state of the thread - read/written directly by JVM */
private volatile boolean interrupted;
/* Fields reserved for exclusive use by the JVM */
private boolean stillborn = false;
private long eetop;
/* What will be run. */
private Runnable target;
/* The group of this thread */
private ThreadGroup group;
/* The context ClassLoader for this thread */
private ClassLoader contextClassLoader;
/* The inherited AccessControlContext of this thread */
@SuppressWarnings("removal")
private AccessControlContext inheritedAccessControlContext;
/* For autonumbering anonymous threads. */
private static int threadInitNumber;
private static synchronized int nextThreadNum() {
return threadInitNumber++;
}
/* ThreadLocal values pertaining to this thread. This map is maintained
* by the ThreadLocal class. */
ThreadLocal.ThreadLocalMap threadLocals = null;
/*
* InheritableThreadLocal values pertaining to this thread. This map is
* maintained by the InheritableThreadLocal class.
*/
ThreadLocal.ThreadLocalMap inheritableThreadLocals = null;
/*
* The requested stack size for this thread, or 0 if the creator did
* not specify a stack size. It is up to the VM to do whatever it
* likes with this number; some VMs will ignore it.
*/
private final long stackSize;
/*
* Thread ID
*/
private final long tid;
/* For generating thread ID */
private static long threadSeqNumber;
private static synchronized long nextThreadID() {
return ++threadSeqNumber;
}
/*
* Java thread status for tools, default indicates thread 'not yet started'
*/
private volatile int threadStatus;
/**
* The argument supplied to the current call to
* java.util.concurrent.locks.LockSupport.park.
* Set by (private) java.util.concurrent.locks.LockSupport.setBlocker
* Accessed using java.util.concurrent.locks.LockSupport.getBlocker
*/
volatile Object parkBlocker;
/* The object in which this thread is blocked in an interruptible I/O
* operation, if any. The blocker's interrupt method should be invoked
* after setting this thread's interrupt status.
*/
private volatile Interruptible blocker;
private final Object blockerLock = new Object();
/* Set the blocker field; invoked via jdk.internal.access.SharedSecrets
* from java.nio code
*/
static void blockedOn(Interruptible b) {
Thread me = Thread.currentThread();
synchronized (me.blockerLock) {
me.blocker = b;
}
}
/**
* The minimum priority that a thread can have.
*/
public static final int MIN_PRIORITY = 1;
/**
* The default priority that is assigned to a thread.
*/
public static final int NORM_PRIORITY = 5;
/**
* The maximum priority that a thread can have.
*/
public static final int MAX_PRIORITY = 10;
/**
* Returns a reference to the currently executing thread object.
*
* @return the currently executing thread.
*/
@IntrinsicCandidate
public static native Thread currentThread();
/**
* A hint to the scheduler that the current thread is willing to yield
* its current use of a processor. The scheduler is free to ignore this
* hint.
*
* Yield is a heuristic attempt to improve relative progression
* between threads that would otherwise over-utilise a CPU. Its use
* should be combined with detailed profiling and benchmarking to
* ensure that it actually has the desired effect.
*
*
It is rarely appropriate to use this method. It may be useful
* for debugging or testing purposes, where it may help to reproduce
* bugs due to race conditions. It may also be useful when designing
* concurrency control constructs such as the ones in the
* {@link java.util.concurrent.locks} package.
*/
public static native void yield();
/**
* Causes the currently executing thread to sleep (temporarily cease
* execution) for the specified number of milliseconds, subject to
* the precision and accuracy of system timers and schedulers. The thread
* does not lose ownership of any monitors.
*
* @param millis
* the length of time to sleep in milliseconds
*
* @throws IllegalArgumentException
* if the value of {@code millis} is negative
*
* @throws InterruptedException
* if any thread has interrupted the current thread. The
* interrupted status of the current thread is
* cleared when this exception is thrown.
*/
public static native void sleep(long millis) throws InterruptedException;
/**
* Causes the currently executing thread to sleep (temporarily cease
* execution) for the specified number of milliseconds plus the specified
* number of nanoseconds, subject to the precision and accuracy of system
* timers and schedulers. The thread does not lose ownership of any
* monitors.
*
* @param millis
* the length of time to sleep in milliseconds
*
* @param nanos
* {@code 0-999999} additional nanoseconds to sleep
*
* @throws IllegalArgumentException
* if the value of {@code millis} is negative, or the value of
* {@code nanos} is not in the range {@code 0-999999}
*
* @throws InterruptedException
* if any thread has interrupted the current thread. The
* interrupted status of the current thread is
* cleared when this exception is thrown.
*/
public static void sleep(long millis, int nanos)
throws InterruptedException {
if (millis < 0) {
throw new IllegalArgumentException("timeout value is negative");
}
if (nanos < 0 || nanos > 999999) {
throw new IllegalArgumentException(
"nanosecond timeout value out of range");
}
if (nanos > 0 && millis < Long.MAX_VALUE) {
millis++;
}
sleep(millis);
}
/**
* Indicates that the caller is momentarily unable to progress, until the
* occurrence of one or more actions on the part of other activities. By
* invoking this method within each iteration of a spin-wait loop construct,
* the calling thread indicates to the runtime that it is busy-waiting.
* The runtime may take action to improve the performance of invoking
* spin-wait loop constructions.
*
* @apiNote
* As an example consider a method in a class that spins in a loop until
* some flag is set outside of that method. A call to the {@code onSpinWait}
* method should be placed inside the spin loop.
*
{@code
* class EventHandler {
* volatile boolean eventNotificationNotReceived;
* void waitForEventAndHandleIt() {
* while ( eventNotificationNotReceived ) {
* java.lang.Thread.onSpinWait();
* }
* readAndProcessEvent();
* }
*
* void readAndProcessEvent() {
* // Read event from some source and process it
* . . .
* }
* }
* }
*
* The code above would remain correct even if the {@code onSpinWait}
* method was not called at all. However on some architectures the Java
* Virtual Machine may issue the processor instructions to address such
* code patterns in a more beneficial way.
*
* @since 9
*/
@IntrinsicCandidate
public static void onSpinWait() {}
/**
* Initializes a Thread.
*
* @param g the Thread group
* @param target the object whose run() method gets called
* @param name the name of the new Thread
* @param stackSize the desired stack size for the new thread, or
* zero to indicate that this parameter is to be ignored.
* @param acc the AccessControlContext to inherit, or
* AccessController.getContext() if null
* @param inheritThreadLocals if {@code true}, inherit initial values for
* inheritable thread-locals from the constructing thread
*/
@SuppressWarnings("removal")
private Thread(ThreadGroup g, Runnable target, String name,
long stackSize, AccessControlContext acc,
boolean inheritThreadLocals) {
if (name == null) {
throw new NullPointerException("name cannot be null");
}
this.name = name;
Thread parent = currentThread();
SecurityManager security = System.getSecurityManager();
if (g == null) {
/* Determine if it's an applet or not */
/* If there is a security manager, ask the security manager
what to do. */
if (security != null) {
g = security.getThreadGroup();
}
/* If the security manager doesn't have a strong opinion
on the matter, use the parent thread group. */
if (g == null) {
g = parent.getThreadGroup();
}
}
/* checkAccess regardless of whether or not threadgroup is
explicitly passed in. */
g.checkAccess();
/*
* Do we have the required permissions?
*/
if (security != null) {
if (isCCLOverridden(getClass())) {
security.checkPermission(
SecurityConstants.SUBCLASS_IMPLEMENTATION_PERMISSION);
}
}
g.addUnstarted();
this.group = g;
this.daemon = parent.isDaemon();
this.priority = parent.getPriority();
if (security == null || isCCLOverridden(parent.getClass()))
this.contextClassLoader = parent.getContextClassLoader();
else
this.contextClassLoader = parent.contextClassLoader;
this.inheritedAccessControlContext =
acc != null ? acc : AccessController.getContext();
this.target = target;
setPriority(priority);
if (inheritThreadLocals && parent.inheritableThreadLocals != null)
this.inheritableThreadLocals =
ThreadLocal.createInheritedMap(parent.inheritableThreadLocals);
/* Stash the specified stack size in case the VM cares */
this.stackSize = stackSize;
/* Set thread ID */
this.tid = nextThreadID();
}
/**
* Throws CloneNotSupportedException as a Thread can not be meaningfully
* cloned. Construct a new Thread instead.
*
* @throws CloneNotSupportedException
* always
*/
@Override
protected Object clone() throws CloneNotSupportedException {
throw new CloneNotSupportedException();
}
/**
* Allocates a new {@code Thread} object. This constructor has the same
* effect as {@linkplain #Thread(ThreadGroup,Runnable,String) Thread}
* {@code (null, null, gname)}, where {@code gname} is a newly generated
* name. Automatically generated names are of the form
* {@code "Thread-"+}n, where n is an integer.
*/
public Thread() {
this(null, null, "Thread-" + nextThreadNum(), 0);
}
/**
* Allocates a new {@code Thread} object. This constructor has the same
* effect as {@linkplain #Thread(ThreadGroup,Runnable,String) Thread}
* {@code (null, target, gname)}, where {@code gname} is a newly generated
* name. Automatically generated names are of the form
* {@code "Thread-"+}n, where n is an integer.
*
* @param target
* the object whose {@code run} method is invoked when this thread
* is started. If {@code null}, this classes {@code run} method does
* nothing.
*/
public Thread(Runnable target) {
this(null, target, "Thread-" + nextThreadNum(), 0);
}
/**
* Creates a new Thread that inherits the given AccessControlContext
* but thread-local variables are not inherited.
* This is not a public constructor.
*/
Thread(Runnable target, @SuppressWarnings("removal") AccessControlContext acc) {
this(null, target, "Thread-" + nextThreadNum(), 0, acc, false);
}
/**
* Allocates a new {@code Thread} object. This constructor has the same
* effect as {@linkplain #Thread(ThreadGroup,Runnable,String) Thread}
* {@code (group, target, gname)} ,where {@code gname} is a newly generated
* name. Automatically generated names are of the form
* {@code "Thread-"+}n, where n is an integer.
*
* @param group
* the thread group. If {@code null} and there is a security
* manager, the group is determined by {@linkplain
* SecurityManager#getThreadGroup SecurityManager.getThreadGroup()}.
* If there is not a security manager or {@code
* SecurityManager.getThreadGroup()} returns {@code null}, the group
* is set to the current thread's thread group.
*
* @param target
* the object whose {@code run} method is invoked when this thread
* is started. If {@code null}, this thread's run method is invoked.
*
* @throws SecurityException
* if the current thread cannot create a thread in the specified
* thread group
*/
public Thread(ThreadGroup group, Runnable target) {
this(group, target, "Thread-" + nextThreadNum(), 0);
}
/**
* Allocates a new {@code Thread} object. This constructor has the same
* effect as {@linkplain #Thread(ThreadGroup,Runnable,String) Thread}
* {@code (null, null, name)}.
*
* @param name
* the name of the new thread
*/
public Thread(String name) {
this(null, null, name, 0);
}
/**
* Allocates a new {@code Thread} object. This constructor has the same
* effect as {@linkplain #Thread(ThreadGroup,Runnable,String) Thread}
* {@code (group, null, name)}.
*
* @param group
* the thread group. If {@code null} and there is a security
* manager, the group is determined by {@linkplain
* SecurityManager#getThreadGroup SecurityManager.getThreadGroup()}.
* If there is not a security manager or {@code
* SecurityManager.getThreadGroup()} returns {@code null}, the group
* is set to the current thread's thread group.
*
* @param name
* the name of the new thread
*
* @throws SecurityException
* if the current thread cannot create a thread in the specified
* thread group
*/
public Thread(ThreadGroup group, String name) {
this(group, null, name, 0);
}
/**
* Allocates a new {@code Thread} object. This constructor has the same
* effect as {@linkplain #Thread(ThreadGroup,Runnable,String) Thread}
* {@code (null, target, name)}.
*
* @param target
* the object whose {@code run} method is invoked when this thread
* is started. If {@code null}, this thread's run method is invoked.
*
* @param name
* the name of the new thread
*/
public Thread(Runnable target, String name) {
this(null, target, name, 0);
}
/**
* Allocates a new {@code Thread} object so that it has {@code target}
* as its run object, has the specified {@code name} as its name,
* and belongs to the thread group referred to by {@code group}.
*
*
If there is a security manager, its
* {@link SecurityManager#checkAccess(ThreadGroup) checkAccess}
* method is invoked with the ThreadGroup as its argument.
*
*
In addition, its {@code checkPermission} method is invoked with
* the {@code RuntimePermission("enableContextClassLoaderOverride")}
* permission when invoked directly or indirectly by the constructor
* of a subclass which overrides the {@code getContextClassLoader}
* or {@code setContextClassLoader} methods.
*
*
The priority of the newly created thread is set equal to the
* priority of the thread creating it, that is, the currently running
* thread. The method {@linkplain #setPriority setPriority} may be
* used to change the priority to a new value.
*
*
The newly created thread is initially marked as being a daemon
* thread if and only if the thread creating it is currently marked
* as a daemon thread. The method {@linkplain #setDaemon setDaemon}
* may be used to change whether or not a thread is a daemon.
*
* @param group
* the thread group. If {@code null} and there is a security
* manager, the group is determined by {@linkplain
* SecurityManager#getThreadGroup SecurityManager.getThreadGroup()}.
* If there is not a security manager or {@code
* SecurityManager.getThreadGroup()} returns {@code null}, the group
* is set to the current thread's thread group.
*
* @param target
* the object whose {@code run} method is invoked when this thread
* is started. If {@code null}, this thread's run method is invoked.
*
* @param name
* the name of the new thread
*
* @throws SecurityException
* if the current thread cannot create a thread in the specified
* thread group or cannot override the context class loader methods.
*/
public Thread(ThreadGroup group, Runnable target, String name) {
this(group, target, name, 0);
}
/**
* Allocates a new {@code Thread} object so that it has {@code target}
* as its run object, has the specified {@code name} as its name,
* and belongs to the thread group referred to by {@code group}, and has
* the specified stack size.
*
*
This constructor is identical to {@link
* #Thread(ThreadGroup,Runnable,String)} with the exception of the fact
* that it allows the thread stack size to be specified. The stack size
* is the approximate number of bytes of address space that the virtual
* machine is to allocate for this thread's stack. The effect of the
* {@code stackSize} parameter, if any, is highly platform dependent.
*
*
On some platforms, specifying a higher value for the
* {@code stackSize} parameter may allow a thread to achieve greater
* recursion depth before throwing a {@link StackOverflowError}.
* Similarly, specifying a lower value may allow a greater number of
* threads to exist concurrently without throwing an {@link
* OutOfMemoryError} (or other internal error). The details of
* the relationship between the value of the {@code stackSize} parameter
* and the maximum recursion depth and concurrency level are
* platform-dependent. On some platforms, the value of the
* {@code stackSize} parameter may have no effect whatsoever.
*
*
The virtual machine is free to treat the {@code stackSize}
* parameter as a suggestion. If the specified value is unreasonably low
* for the platform, the virtual machine may instead use some
* platform-specific minimum value; if the specified value is unreasonably
* high, the virtual machine may instead use some platform-specific
* maximum. Likewise, the virtual machine is free to round the specified
* value up or down as it sees fit (or to ignore it completely).
*
*
Specifying a value of zero for the {@code stackSize} parameter will
* cause this constructor to behave exactly like the
* {@code Thread(ThreadGroup, Runnable, String)} constructor.
*
*
Due to the platform-dependent nature of the behavior of this
* constructor, extreme care should be exercised in its use.
* The thread stack size necessary to perform a given computation will
* likely vary from one JRE implementation to another. In light of this
* variation, careful tuning of the stack size parameter may be required,
* and the tuning may need to be repeated for each JRE implementation on
* which an application is to run.
*
*
Implementation note: Java platform implementers are encouraged to
* document their implementation's behavior with respect to the
* {@code stackSize} parameter.
*
*
* @param group
* the thread group. If {@code null} and there is a security
* manager, the group is determined by {@linkplain
* SecurityManager#getThreadGroup SecurityManager.getThreadGroup()}.
* If there is not a security manager or {@code
* SecurityManager.getThreadGroup()} returns {@code null}, the group
* is set to the current thread's thread group.
*
* @param target
* the object whose {@code run} method is invoked when this thread
* is started. If {@code null}, this thread's run method is invoked.
*
* @param name
* the name of the new thread
*
* @param stackSize
* the desired stack size for the new thread, or zero to indicate
* that this parameter is to be ignored.
*
* @throws SecurityException
* if the current thread cannot create a thread in the specified
* thread group
*
* @since 1.4
*/
public Thread(ThreadGroup group, Runnable target, String name,
long stackSize) {
this(group, target, name, stackSize, null, true);
}
/**
* Allocates a new {@code Thread} object so that it has {@code target}
* as its run object, has the specified {@code name} as its name,
* belongs to the thread group referred to by {@code group}, has
* the specified {@code stackSize}, and inherits initial values for
* {@linkplain InheritableThreadLocal inheritable thread-local} variables
* if {@code inheritThreadLocals} is {@code true}.
*
*
This constructor is identical to {@link
* #Thread(ThreadGroup,Runnable,String,long)} with the added ability to
* suppress, or not, the inheriting of initial values for inheritable
* thread-local variables from the constructing thread. This allows for
* finer grain control over inheritable thread-locals. Care must be taken
* when passing a value of {@code false} for {@code inheritThreadLocals},
* as it may lead to unexpected behavior if the new thread executes code
* that expects a specific thread-local value to be inherited.
*
*
Specifying a value of {@code true} for the {@code inheritThreadLocals}
* parameter will cause this constructor to behave exactly like the
* {@code Thread(ThreadGroup, Runnable, String, long)} constructor.
*
* @param group
* the thread group. If {@code null} and there is a security
* manager, the group is determined by {@linkplain
* SecurityManager#getThreadGroup SecurityManager.getThreadGroup()}.
* If there is not a security manager or {@code
* SecurityManager.getThreadGroup()} returns {@code null}, the group
* is set to the current thread's thread group.
*
* @param target
* the object whose {@code run} method is invoked when this thread
* is started. If {@code null}, this thread's run method is invoked.
*
* @param name
* the name of the new thread
*
* @param stackSize
* the desired stack size for the new thread, or zero to indicate
* that this parameter is to be ignored
*
* @param inheritThreadLocals
* if {@code true}, inherit initial values for inheritable
* thread-locals from the constructing thread, otherwise no initial
* values are inherited
*
* @throws SecurityException
* if the current thread cannot create a thread in the specified
* thread group
*
* @since 9
*/
public Thread(ThreadGroup group, Runnable target, String name,
long stackSize, boolean inheritThreadLocals) {
this(group, target, name, stackSize, null, inheritThreadLocals);
}
/**
* Causes this thread to begin execution; the Java Virtual Machine
* calls the {@code run} method of this thread.
*
* The result is that two threads are running concurrently: the
* current thread (which returns from the call to the
* {@code start} method) and the other thread (which executes its
* {@code run} method).
*
* It is never legal to start a thread more than once.
* In particular, a thread may not be restarted once it has completed
* execution.
*
* @throws IllegalThreadStateException if the thread was already started.
* @see #run()
* @see #stop()
*/
public synchronized void start() {
/**
* This method is not invoked for the main method thread or "system"
* group threads created/set up by the VM. Any new functionality added
* to this method in the future may have to also be added to the VM.
*
* A zero status value corresponds to state "NEW".
*/
if (threadStatus != 0)
throw new IllegalThreadStateException();
/* Notify the group that this thread is about to be started
* so that it can be added to the group's list of threads
* and the group's unstarted count can be decremented. */
group.add(this);
boolean started = false;
try {
start0();
started = true;
} finally {
try {
if (!started) {
group.threadStartFailed(this);
}
} catch (Throwable ignore) {
/* do nothing. If start0 threw a Throwable then
it will be passed up the call stack */
}
}
}
private native void start0();
/**
* If this thread was constructed using a separate
* {@code Runnable} run object, then that
* {@code Runnable} object's {@code run} method is called;
* otherwise, this method does nothing and returns.
*
* Subclasses of {@code Thread} should override this method.
*
* @see #start()
* @see #stop()
* @see #Thread(ThreadGroup, Runnable, String)
*/
@Override
public void run() {
if (target != null) {
target.run();
}
}
/**
* This method is called by the system to give a Thread
* a chance to clean up before it actually exits.
*/
private void exit() {
if (threadLocals != null && TerminatingThreadLocal.REGISTRY.isPresent()) {
TerminatingThreadLocal.threadTerminated();
}
if (group != null) {
group.threadTerminated(this);
group = null;
}
/* Aggressively null out all reference fields: see bug 4006245 */
target = null;
/* Speed the release of some of these resources */
threadLocals = null;
inheritableThreadLocals = null;
inheritedAccessControlContext = null;
blocker = null;
uncaughtExceptionHandler = null;
}
/**
* Forces the thread to stop executing.
*
* If there is a security manager installed, its {@code checkAccess}
* method is called with {@code this}
* as its argument. This may result in a
* {@code SecurityException} being raised (in the current thread).
*
* If this thread is different from the current thread (that is, the current
* thread is trying to stop a thread other than itself), the
* security manager's {@code checkPermission} method (with a
* {@code RuntimePermission("stopThread")} argument) is called in
* addition.
* Again, this may result in throwing a
* {@code SecurityException} (in the current thread).
*
* The thread represented by this thread is forced to stop whatever
* it is doing abnormally and to throw a newly created
* {@code ThreadDeath} object as an exception.
*
* It is permitted to stop a thread that has not yet been started.
* If the thread is eventually started, it immediately terminates.
*
* An application should not normally try to catch
* {@code ThreadDeath} unless it must do some extraordinary
* cleanup operation (note that the throwing of
* {@code ThreadDeath} causes {@code finally} clauses of
* {@code try} statements to be executed before the thread
* officially dies). If a {@code catch} clause catches a
* {@code ThreadDeath} object, it is important to rethrow the
* object so that the thread actually dies.
*
* The top-level error handler that reacts to otherwise uncaught
* exceptions does not print out a message or otherwise notify the
* application if the uncaught exception is an instance of
* {@code ThreadDeath}.
*
* @throws SecurityException if the current thread cannot
* modify this thread.
* @see #interrupt()
* @see #checkAccess()
* @see #run()
* @see #start()
* @see ThreadDeath
* @see ThreadGroup#uncaughtException(Thread,Throwable)
* @see SecurityManager#checkAccess(Thread)
* @see SecurityManager#checkPermission
* @deprecated This method is inherently unsafe. Stopping a thread with
* Thread.stop causes it to unlock all of the monitors that it
* has locked (as a natural consequence of the unchecked
* {@code ThreadDeath} exception propagating up the stack). If
* any of the objects previously protected by these monitors were in
* an inconsistent state, the damaged objects become visible to
* other threads, potentially resulting in arbitrary behavior. Many
* uses of {@code stop} should be replaced by code that simply
* modifies some variable to indicate that the target thread should
* stop running. The target thread should check this variable
* regularly, and return from its run method in an orderly fashion
* if the variable indicates that it is to stop running. If the
* target thread waits for long periods (on a condition variable,
* for example), the {@code interrupt} method should be used to
* interrupt the wait.
* For more information, see
* Why
* are Thread.stop, Thread.suspend and Thread.resume Deprecated?.
*/
@Deprecated(since="1.2")
public final void stop() {
@SuppressWarnings("removal")
SecurityManager security = System.getSecurityManager();
if (security != null) {
checkAccess();
if (this != Thread.currentThread()) {
security.checkPermission(SecurityConstants.STOP_THREAD_PERMISSION);
}
}
// A zero status value corresponds to "NEW", it can't change to
// not-NEW because we hold the lock.
if (threadStatus != 0) {
resume(); // Wake up thread if it was suspended; no-op otherwise
}
// The VM can handle all thread states
stop0(new ThreadDeath());
}
/**
* Interrupts this thread.
*
*
Unless the current thread is interrupting itself, which is
* always permitted, the {@link #checkAccess() checkAccess} method
* of this thread is invoked, which may cause a {@link
* SecurityException} to be thrown.
*
*
If this thread is blocked in an invocation of the {@link
* Object#wait() wait()}, {@link Object#wait(long) wait(long)}, or {@link
* Object#wait(long, int) wait(long, int)} methods of the {@link Object}
* class, or of the {@link #join()}, {@link #join(long)}, {@link
* #join(long, int)}, {@link #sleep(long)}, or {@link #sleep(long, int)}
* methods of this class, then its interrupt status will be cleared and it
* will receive an {@link InterruptedException}.
*
*
If this thread is blocked in an I/O operation upon an {@link
* java.nio.channels.InterruptibleChannel InterruptibleChannel}
* then the channel will be closed, the thread's interrupt
* status will be set, and the thread will receive a {@link
* java.nio.channels.ClosedByInterruptException}.
*
*
If this thread is blocked in a {@link java.nio.channels.Selector}
* then the thread's interrupt status will be set and it will return
* immediately from the selection operation, possibly with a non-zero
* value, just as if the selector's {@link
* java.nio.channels.Selector#wakeup wakeup} method were invoked.
*
*
If none of the previous conditions hold then this thread's interrupt
* status will be set.
*
* Interrupting a thread that is not alive need not have any effect.
*
* @implNote In the JDK Reference Implementation, interruption of a thread
* that is not alive still records that the interrupt request was made and
* will report it via {@link #interrupted} and {@link #isInterrupted()}.
*
* @throws SecurityException
* if the current thread cannot modify this thread
*
* @revised 6.0, 14
*/
public void interrupt() {
if (this != Thread.currentThread()) {
checkAccess();
// thread may be blocked in an I/O operation
synchronized (blockerLock) {
Interruptible b = blocker;
if (b != null) {
interrupted = true;
interrupt0(); // inform VM of interrupt
b.interrupt(this);
return;
}
}
}
interrupted = true;
// inform VM of interrupt
interrupt0();
}
/**
* Tests whether the current thread has been interrupted. The
* interrupted status of the thread is cleared by this method. In
* other words, if this method were to be called twice in succession, the
* second call would return false (unless the current thread were
* interrupted again, after the first call had cleared its interrupted
* status and before the second call had examined it).
*
* @return {@code true} if the current thread has been interrupted;
* {@code false} otherwise.
* @see #isInterrupted()
* @revised 6.0, 14
*/
public static boolean interrupted() {
Thread t = currentThread();
boolean interrupted = t.interrupted;
// We may have been interrupted the moment after we read the field,
// so only clear the field if we saw that it was set and will return
// true; otherwise we could lose an interrupt.
if (interrupted) {
t.interrupted = false;
clearInterruptEvent();
}
return interrupted;
}
/**
* Tests whether this thread has been interrupted. The interrupted
* status of the thread is unaffected by this method.
*
* @return {@code true} if this thread has been interrupted;
* {@code false} otherwise.
* @see #interrupted()
* @revised 6.0, 14
*/
public boolean isInterrupted() {
return interrupted;
}
/**
* Tests if this thread is alive. A thread is alive if it has
* been started and has not yet died.
*
* @return {@code true} if this thread is alive;
* {@code false} otherwise.
*/
public final native boolean isAlive();
/**
* Suspends this thread.
*
* First, the {@code checkAccess} method of this thread is called
* with no arguments. This may result in throwing a
* {@code SecurityException }(in the current thread).
*
* If the thread is alive, it is suspended and makes no further
* progress unless and until it is resumed.
*
* @throws SecurityException if the current thread cannot modify
* this thread.
* @see #checkAccess
* @deprecated This method has been deprecated, as it is
* inherently deadlock-prone. If the target thread holds a lock on the
* monitor protecting a critical system resource when it is suspended, no
* thread can access this resource until the target thread is resumed. If
* the thread that would resume the target thread attempts to lock this
* monitor prior to calling {@code resume}, deadlock results. Such
* deadlocks typically manifest themselves as "frozen" processes.
* For more information, see
* Why
* are Thread.stop, Thread.suspend and Thread.resume Deprecated?.
*/
@Deprecated(since="1.2", forRemoval=true)
public final void suspend() {
checkAccess();
suspend0();
}
/**
* Resumes a suspended thread.
*
* First, the {@code checkAccess} method of this thread is called
* with no arguments. This may result in throwing a
* {@code SecurityException} (in the current thread).
*
* If the thread is alive but suspended, it is resumed and is
* permitted to make progress in its execution.
*
* @throws SecurityException if the current thread cannot modify this
* thread.
* @see #checkAccess
* @see #suspend()
* @deprecated This method exists solely for use with {@link #suspend},
* which has been deprecated because it is deadlock-prone.
* For more information, see
* Why
* are Thread.stop, Thread.suspend and Thread.resume Deprecated?.
*/
@Deprecated(since="1.2", forRemoval=true)
public final void resume() {
checkAccess();
resume0();
}
/**
* Changes the priority of this thread.
*
* First the {@code checkAccess} method of this thread is called
* with no arguments. This may result in throwing a {@code SecurityException}.
*
* Otherwise, the priority of this thread is set to the smaller of
* the specified {@code newPriority} and the maximum permitted
* priority of the thread's thread group.
*
* @param newPriority priority to set this thread to
* @throws IllegalArgumentException If the priority is not in the
* range {@code MIN_PRIORITY} to
* {@code MAX_PRIORITY}.
* @throws SecurityException if the current thread cannot modify
* this thread.
* @see #getPriority
* @see #checkAccess()
* @see #getThreadGroup()
* @see #MAX_PRIORITY
* @see #MIN_PRIORITY
* @see ThreadGroup#getMaxPriority()
*/
public final void setPriority(int newPriority) {
ThreadGroup g;
checkAccess();
if (newPriority > MAX_PRIORITY || newPriority < MIN_PRIORITY) {
throw new IllegalArgumentException();
}
if((g = getThreadGroup()) != null) {
if (newPriority > g.getMaxPriority()) {
newPriority = g.getMaxPriority();
}
setPriority0(priority = newPriority);
}
}
/**
* Returns this thread's priority.
*
* @return this thread's priority.
* @see #setPriority
*/
public final int getPriority() {
return priority;
}
/**
* Changes the name of this thread to be equal to the argument {@code name}.
*
* First the {@code checkAccess} method of this thread is called
* with no arguments. This may result in throwing a
* {@code SecurityException}.
*
* @param name the new name for this thread.
* @throws SecurityException if the current thread cannot modify this
* thread.
* @see #getName
* @see #checkAccess()
*/
public final synchronized void setName(String name) {
checkAccess();
if (name == null) {
throw new NullPointerException("name cannot be null");
}
this.name = name;
if (threadStatus != 0) {
setNativeName(name);
}
}
/**
* Returns this thread's name.
*
* @return this thread's name.
* @see #setName(String)
*/
public final String getName() {
return name;
}
/**
* Returns the thread group to which this thread belongs.
* This method returns null if this thread has died
* (been stopped).
*
* @return this thread's thread group.
*/
public final ThreadGroup getThreadGroup() {
return group;
}
/**
* Returns an estimate of the number of active threads in the current
* thread's {@linkplain java.lang.ThreadGroup thread group} and its
* subgroups. Recursively iterates over all subgroups in the current
* thread's thread group.
*
*
The value returned is only an estimate because the number of
* threads may change dynamically while this method traverses internal
* data structures, and might be affected by the presence of certain
* system threads. This method is intended primarily for debugging
* and monitoring purposes.
*
* @return an estimate of the number of active threads in the current
* thread's thread group and in any other thread group that
* has the current thread's thread group as an ancestor
*/
public static int activeCount() {
return currentThread().getThreadGroup().activeCount();
}
/**
* Copies into the specified array every active thread in the current
* thread's thread group and its subgroups. This method simply
* invokes the {@link java.lang.ThreadGroup#enumerate(Thread[])}
* method of the current thread's thread group.
*
*
An application might use the {@linkplain #activeCount activeCount}
* method to get an estimate of how big the array should be, however
* if the array is too short to hold all the threads, the extra threads
* are silently ignored. If it is critical to obtain every active
* thread in the current thread's thread group and its subgroups, the
* invoker should verify that the returned int value is strictly less
* than the length of {@code tarray}.
*
*
Due to the inherent race condition in this method, it is recommended
* that the method only be used for debugging and monitoring purposes.
*
* @param tarray
* an array into which to put the list of threads
*
* @return the number of threads put into the array
*
* @throws SecurityException
* if {@link java.lang.ThreadGroup#checkAccess} determines that
* the current thread cannot access its thread group
*/
public static int enumerate(Thread tarray[]) {
return currentThread().getThreadGroup().enumerate(tarray);
}
/**
* Throws {@code UnsupportedOperationException}.
*
* @return nothing
*
* @deprecated This method was originally designed to count the number of
* stack frames but the results were never well-defined and it
* depended on thread-suspension.
* This method is subject to removal in a future version of Java SE.
* @see StackWalker
*/
@Deprecated(since="1.2", forRemoval=true)
public int countStackFrames() {
throw new UnsupportedOperationException();
}
/**
* Waits at most {@code millis} milliseconds for this thread to
* die. A timeout of {@code 0} means to wait forever.
*
*
This implementation uses a loop of {@code this.wait} calls
* conditioned on {@code this.isAlive}. As a thread terminates the
* {@code this.notifyAll} method is invoked. It is recommended that
* applications not use {@code wait}, {@code notify}, or
* {@code notifyAll} on {@code Thread} instances.
*
* @param millis
* the time to wait in milliseconds
*
* @throws IllegalArgumentException
* if the value of {@code millis} is negative
*
* @throws InterruptedException
* if any thread has interrupted the current thread. The
* interrupted status of the current thread is
* cleared when this exception is thrown.
*/
public final synchronized void join(final long millis)
throws InterruptedException {
if (millis > 0) {
if (isAlive()) {
final long startTime = System.nanoTime();
long delay = millis;
do {
wait(delay);
} while (isAlive() && (delay = millis -
TimeUnit.NANOSECONDS.toMillis(System.nanoTime() - startTime)) > 0);
}
} else if (millis == 0) {
while (isAlive()) {
wait(0);
}
} else {
throw new IllegalArgumentException("timeout value is negative");
}
}
/**
* Waits at most {@code millis} milliseconds plus
* {@code nanos} nanoseconds for this thread to die.
* If both arguments are {@code 0}, it means to wait forever.
*
*
This implementation uses a loop of {@code this.wait} calls
* conditioned on {@code this.isAlive}. As a thread terminates the
* {@code this.notifyAll} method is invoked. It is recommended that
* applications not use {@code wait}, {@code notify}, or
* {@code notifyAll} on {@code Thread} instances.
*
* @param millis
* the time to wait in milliseconds
*
* @param nanos
* {@code 0-999999} additional nanoseconds to wait
*
* @throws IllegalArgumentException
* if the value of {@code millis} is negative, or the value
* of {@code nanos} is not in the range {@code 0-999999}
*
* @throws InterruptedException
* if any thread has interrupted the current thread. The
* interrupted status of the current thread is
* cleared when this exception is thrown.
*/
public final synchronized void join(long millis, int nanos)
throws InterruptedException {
if (millis < 0) {
throw new IllegalArgumentException("timeout value is negative");
}
if (nanos < 0 || nanos > 999999) {
throw new IllegalArgumentException(
"nanosecond timeout value out of range");
}
if (nanos > 0 && millis < Long.MAX_VALUE) {
millis++;
}
join(millis);
}
/**
* Waits for this thread to die.
*
*
An invocation of this method behaves in exactly the same
* way as the invocation
*
*
* {@linkplain #join(long) join}{@code (0)}
*
*
* @throws InterruptedException
* if any thread has interrupted the current thread. The
* interrupted status of the current thread is
* cleared when this exception is thrown.
*/
public final void join() throws InterruptedException {
join(0);
}
/**
* Prints a stack trace of the current thread to the standard error stream.
* This method is used only for debugging.
*/
public static void dumpStack() {
new Exception("Stack trace").printStackTrace();
}
/**
* Marks this thread as either a {@linkplain #isDaemon daemon} thread
* or a user thread. The Java Virtual Machine exits when the only
* threads running are all daemon threads.
*
* This method must be invoked before the thread is started.
*
* @param on
* if {@code true}, marks this thread as a daemon thread
*
* @throws IllegalThreadStateException
* if this thread is {@linkplain #isAlive alive}
*
* @throws SecurityException
* if {@link #checkAccess} determines that the current
* thread cannot modify this thread
*/
public final void setDaemon(boolean on) {
checkAccess();
if (isAlive()) {
throw new IllegalThreadStateException();
}
daemon = on;
}
/**
* Tests if this thread is a daemon thread.
*
* @return {@code true} if this thread is a daemon thread;
* {@code false} otherwise.
* @see #setDaemon(boolean)
*/
public final boolean isDaemon() {
return daemon;
}
/**
* Determines if the currently running thread has permission to
* modify this thread.
*
* If there is a security manager, its {@code checkAccess} method
* is called with this thread as its argument. This may result in
* throwing a {@code SecurityException}.
*
* @throws SecurityException if the current thread is not allowed to
* access this thread.
* @see SecurityManager#checkAccess(Thread)
* @deprecated This method is only useful in conjunction with
* {@linkplain SecurityManager the Security Manager}, which is
* deprecated and subject to removal in a future release.
* Consequently, this method is also deprecated and subject to
* removal. There is no replacement for the Security Manager or this
* method.
*/
@Deprecated(since="17", forRemoval=true)
public final void checkAccess() {
@SuppressWarnings("removal")
SecurityManager security = System.getSecurityManager();
if (security != null) {
security.checkAccess(this);
}
}
/**
* Returns a string representation of this thread, including the
* thread's name, priority, and thread group.
*
* @return a string representation of this thread.
*/
public String toString() {
ThreadGroup group = getThreadGroup();
if (group != null) {
return "Thread[" + getName() + "," + getPriority() + "," +
group.getName() + "]";
} else {
return "Thread[" + getName() + "," + getPriority() + "," +
"" + "]";
}
}
/**
* Returns the context {@code ClassLoader} for this thread. The context
* {@code ClassLoader} is provided by the creator of the thread for use
* by code running in this thread when loading classes and resources.
* If not {@linkplain #setContextClassLoader set}, the default is the
* {@code ClassLoader} context of the parent thread. The context
* {@code ClassLoader} of the
* primordial thread is typically set to the class loader used to load the
* application.
*
*
* @return the context {@code ClassLoader} for this thread, or {@code null}
* indicating the system class loader (or, failing that, the
* bootstrap class loader)
*
* @throws SecurityException
* if a security manager is present, and the caller's class loader
* is not {@code null} and is not the same as or an ancestor of the
* context class loader, and the caller does not have the
* {@link RuntimePermission}{@code ("getClassLoader")}
*
* @since 1.2
*/
@CallerSensitive
public ClassLoader getContextClassLoader() {
if (contextClassLoader == null)
return null;
@SuppressWarnings("removal")
SecurityManager sm = System.getSecurityManager();
if (sm != null) {
ClassLoader.checkClassLoaderPermission(contextClassLoader,
Reflection.getCallerClass());
}
return contextClassLoader;
}
/**
* Sets the context ClassLoader for this Thread. The context
* ClassLoader can be set when a thread is created, and allows
* the creator of the thread to provide the appropriate class loader,
* through {@code getContextClassLoader}, to code running in the thread
* when loading classes and resources.
*
*
If a security manager is present, its {@link
* SecurityManager#checkPermission(java.security.Permission) checkPermission}
* method is invoked with a {@link RuntimePermission RuntimePermission}{@code
* ("setContextClassLoader")} permission to see if setting the context
* ClassLoader is permitted.
*
* @param cl
* the context ClassLoader for this Thread, or null indicating the
* system class loader (or, failing that, the bootstrap class loader)
*
* @throws SecurityException
* if the current thread cannot set the context ClassLoader
*
* @since 1.2
*/
public void setContextClassLoader(ClassLoader cl) {
@SuppressWarnings("removal")
SecurityManager sm = System.getSecurityManager();
if (sm != null) {
sm.checkPermission(new RuntimePermission("setContextClassLoader"));
}
contextClassLoader = cl;
}
/**
* Returns {@code true} if and only if the current thread holds the
* monitor lock on the specified object.
*
*
This method is designed to allow a program to assert that
* the current thread already holds a specified lock:
*
* assert Thread.holdsLock(obj);
*
*
* @param obj the object on which to test lock ownership
* @throws NullPointerException if obj is {@code null}
* @return {@code true} if the current thread holds the monitor lock on
* the specified object.
* @since 1.4
*/
public static native boolean holdsLock(Object obj);
private static final StackTraceElement[] EMPTY_STACK_TRACE
= new StackTraceElement[0];
/**
* Returns an array of stack trace elements representing the stack dump
* of this thread. This method will return a zero-length array if
* this thread has not started, has started but has not yet been
* scheduled to run by the system, or has terminated.
* If the returned array is of non-zero length then the first element of
* the array represents the top of the stack, which is the most recent
* method invocation in the sequence. The last element of the array
* represents the bottom of the stack, which is the least recent method
* invocation in the sequence.
*
* If there is a security manager, and this thread is not
* the current thread, then the security manager's
* {@code checkPermission} method is called with a
* {@code RuntimePermission("getStackTrace")} permission
* to see if it's ok to get the stack trace.
*
*
Some virtual machines may, under some circumstances, omit one
* or more stack frames from the stack trace. In the extreme case,
* a virtual machine that has no stack trace information concerning
* this thread is permitted to return a zero-length array from this
* method.
*
* @return an array of {@code StackTraceElement},
* each represents one stack frame.
*
* @throws SecurityException
* if a security manager exists and its
* {@code checkPermission} method doesn't allow
* getting the stack trace of thread.
* @see SecurityManager#checkPermission
* @see RuntimePermission
* @see Throwable#getStackTrace
*
* @since 1.5
*/
public StackTraceElement[] getStackTrace() {
if (this != Thread.currentThread()) {
// check for getStackTrace permission
@SuppressWarnings("removal")
SecurityManager security = System.getSecurityManager();
if (security != null) {
security.checkPermission(
SecurityConstants.GET_STACK_TRACE_PERMISSION);
}
// optimization so we do not call into the vm for threads that
// have not yet started or have terminated
if (!isAlive()) {
return EMPTY_STACK_TRACE;
}
StackTraceElement[][] stackTraceArray = dumpThreads(new Thread[] {this});
StackTraceElement[] stackTrace = stackTraceArray[0];
// a thread that was alive during the previous isAlive call may have
// since terminated, therefore not having a stacktrace.
if (stackTrace == null) {
stackTrace = EMPTY_STACK_TRACE;
}
return stackTrace;
} else {
return (new Exception()).getStackTrace();
}
}
/**
* Returns a map of stack traces for all live threads.
* The map keys are threads and each map value is an array of
* {@code StackTraceElement} that represents the stack dump
* of the corresponding {@code Thread}.
* The returned stack traces are in the format specified for
* the {@link #getStackTrace getStackTrace} method.
*
*
The threads may be executing while this method is called.
* The stack trace of each thread only represents a snapshot and
* each stack trace may be obtained at different time. A zero-length
* array will be returned in the map value if the virtual machine has
* no stack trace information about a thread.
*
*
If there is a security manager, then the security manager's
* {@code checkPermission} method is called with a
* {@code RuntimePermission("getStackTrace")} permission as well as
* {@code RuntimePermission("modifyThreadGroup")} permission
* to see if it is ok to get the stack trace of all threads.
*
* @return a {@code Map} from {@code Thread} to an array of
* {@code StackTraceElement} that represents the stack trace of
* the corresponding thread.
*
* @throws SecurityException
* if a security manager exists and its
* {@code checkPermission} method doesn't allow
* getting the stack trace of thread.
* @see #getStackTrace
* @see SecurityManager#checkPermission
* @see RuntimePermission
* @see Throwable#getStackTrace
*
* @since 1.5
*/
public static Map getAllStackTraces() {
// check for getStackTrace permission
@SuppressWarnings("removal")
SecurityManager security = System.getSecurityManager();
if (security != null) {
security.checkPermission(
SecurityConstants.GET_STACK_TRACE_PERMISSION);
security.checkPermission(
SecurityConstants.MODIFY_THREADGROUP_PERMISSION);
}
// Get a snapshot of the list of all threads
Thread[] threads = getThreads();
StackTraceElement[][] traces = dumpThreads(threads);
Map m = new HashMap<>(threads.length);
for (int i = 0; i < threads.length; i++) {
StackTraceElement[] stackTrace = traces[i];
if (stackTrace != null) {
m.put(threads[i], stackTrace);
}
// else terminated so we don't put it in the map
}
return m;
}
/** cache of subclass security audit results */
/* Replace with ConcurrentReferenceHashMap when/if it appears in a future
* release */
private static class Caches {
/** cache of subclass security audit results */
static final ConcurrentMap subclassAudits =
new ConcurrentHashMap<>();
/** queue for WeakReferences to audited subclasses */
static final ReferenceQueue> subclassAuditsQueue =
new ReferenceQueue<>();
}
/**
* Verifies that this (possibly subclass) instance can be constructed
* without violating security constraints: the subclass must not override
* security-sensitive non-final methods, or else the
* "enableContextClassLoaderOverride" RuntimePermission is checked.
*/
private static boolean isCCLOverridden(Class cl) {
if (cl == Thread.class)
return false;
processQueue(Caches.subclassAuditsQueue, Caches.subclassAudits);
WeakClassKey key = new WeakClassKey(cl, Caches.subclassAuditsQueue);
Boolean result = Caches.subclassAudits.get(key);
if (result == null) {
result = Boolean.valueOf(auditSubclass(cl));
Caches.subclassAudits.putIfAbsent(key, result);
}
return result.booleanValue();
}
/**
* Performs reflective checks on given subclass to verify that it doesn't
* override security-sensitive non-final methods. Returns true if the
* subclass overrides any of the methods, false otherwise.
*/
private static boolean auditSubclass(final Class subcl) {
@SuppressWarnings("removal")
Boolean result = AccessController.doPrivileged(
new PrivilegedAction<>() {
public Boolean run() {
for (Class cl = subcl;
cl != Thread.class;
cl = cl.getSuperclass())
{
try {
cl.getDeclaredMethod("getContextClassLoader", new Class[0]);
return Boolean.TRUE;
} catch (NoSuchMethodException ex) {
}
try {
Class[] params = {ClassLoader.class};
cl.getDeclaredMethod("setContextClassLoader", params);
return Boolean.TRUE;
} catch (NoSuchMethodException ex) {
}
}
return Boolean.FALSE;
}
}
);
return result.booleanValue();
}
private static native StackTraceElement[][] dumpThreads(Thread[] threads);
private static native Thread[] getThreads();
/**
* Returns the identifier of this Thread. The thread ID is a positive
* {@code long} number generated when this thread was created.
* The thread ID is unique and remains unchanged during its lifetime.
* When a thread is terminated, this thread ID may be reused.
*
* @return this thread's ID.
* @since 1.5
*/
public long getId() {
return tid;
}
/**
* A thread state. A thread can be in one of the following states:
*
* - {@link #NEW}
* A thread that has not yet started is in this state.
*
* - {@link #RUNNABLE}
* A thread executing in the Java virtual machine is in this state.
*
* - {@link #BLOCKED}
* A thread that is blocked waiting for a monitor lock
* is in this state.
*
* - {@link #WAITING}
* A thread that is waiting indefinitely for another thread to
* perform a particular action is in this state.
*
* - {@link #TIMED_WAITING}
* A thread that is waiting for another thread to perform an action
* for up to a specified waiting time is in this state.
*
* - {@link #TERMINATED}
* A thread that has exited is in this state.
*
*
*
*
* A thread can be in only one state at a given point in time.
* These states are virtual machine states which do not reflect
* any operating system thread states.
*
* @since 1.5
* @see #getState
*/
public enum State {
/**
* Thread state for a thread which has not yet started.
*/
NEW,
/**
* Thread state for a runnable thread. A thread in the runnable
* state is executing in the Java virtual machine but it may
* be waiting for other resources from the operating system
* such as processor.
*/
RUNNABLE,
/**
* Thread state for a thread blocked waiting for a monitor lock.
* A thread in the blocked state is waiting for a monitor lock
* to enter a synchronized block/method or
* reenter a synchronized block/method after calling
* {@link Object#wait() Object.wait}.
*/
BLOCKED,
/**
* Thread state for a waiting thread.
* A thread is in the waiting state due to calling one of the
* following methods:
*
* - {@link Object#wait() Object.wait} with no timeout
* - {@link #join() Thread.join} with no timeout
* - {@link LockSupport#park() LockSupport.park}
*
*
* A thread in the waiting state is waiting for another thread to
* perform a particular action.
*
* For example, a thread that has called {@code Object.wait()}
* on an object is waiting for another thread to call
* {@code Object.notify()} or {@code Object.notifyAll()} on
* that object. A thread that has called {@code Thread.join()}
* is waiting for a specified thread to terminate.
*/
WAITING,
/**
* Thread state for a waiting thread with a specified waiting time.
* A thread is in the timed waiting state due to calling one of
* the following methods with a specified positive waiting time:
*
* - {@link #sleep Thread.sleep}
* - {@link Object#wait(long) Object.wait} with timeout
* - {@link #join(long) Thread.join} with timeout
* - {@link LockSupport#parkNanos LockSupport.parkNanos}
* - {@link LockSupport#parkUntil LockSupport.parkUntil}
*
*/
TIMED_WAITING,
/**
* Thread state for a terminated thread.
* The thread has completed execution.
*/
TERMINATED;
}
/**
* Returns the state of this thread.
* This method is designed for use in monitoring of the system state,
* not for synchronization control.
*
* @return this thread's state.
* @since 1.5
*/
public State getState() {
// get current thread state
return jdk.internal.misc.VM.toThreadState(threadStatus);
}
// Added in JSR-166
/**
* Interface for handlers invoked when a {@code Thread} abruptly
* terminates due to an uncaught exception.
* When a thread is about to terminate due to an uncaught exception
* the Java Virtual Machine will query the thread for its
* {@code UncaughtExceptionHandler} using
* {@link #getUncaughtExceptionHandler} and will invoke the handler's
* {@code uncaughtException} method, passing the thread and the
* exception as arguments.
* If a thread has not had its {@code UncaughtExceptionHandler}
* explicitly set, then its {@code ThreadGroup} object acts as its
* {@code UncaughtExceptionHandler}. If the {@code ThreadGroup} object
* has no
* special requirements for dealing with the exception, it can forward
* the invocation to the {@linkplain #getDefaultUncaughtExceptionHandler
* default uncaught exception handler}.
*
* @see #setDefaultUncaughtExceptionHandler
* @see #setUncaughtExceptionHandler
* @see ThreadGroup#uncaughtException
* @since 1.5
*/
@FunctionalInterface
public interface UncaughtExceptionHandler {
/**
* Method invoked when the given thread terminates due to the
* given uncaught exception.
*
Any exception thrown by this method will be ignored by the
* Java Virtual Machine.
* @param t the thread
* @param e the exception
*/
void uncaughtException(Thread t, Throwable e);
}
// null unless explicitly set
private volatile UncaughtExceptionHandler uncaughtExceptionHandler;
// null unless explicitly set
private static volatile UncaughtExceptionHandler defaultUncaughtExceptionHandler;
/**
* Set the default handler invoked when a thread abruptly terminates
* due to an uncaught exception, and no other handler has been defined
* for that thread.
*
*
Uncaught exception handling is controlled first by the thread, then
* by the thread's {@link ThreadGroup} object and finally by the default
* uncaught exception handler. If the thread does not have an explicit
* uncaught exception handler set, and the thread's thread group
* (including parent thread groups) does not specialize its
* {@code uncaughtException} method, then the default handler's
* {@code uncaughtException} method will be invoked.
*
By setting the default uncaught exception handler, an application
* can change the way in which uncaught exceptions are handled (such as
* logging to a specific device, or file) for those threads that would
* already accept whatever "default" behavior the system
* provided.
*
*
Note that the default uncaught exception handler should not usually
* defer to the thread's {@code ThreadGroup} object, as that could cause
* infinite recursion.
*
* @param eh the object to use as the default uncaught exception handler.
* If {@code null} then there is no default handler.
*
* @throws SecurityException if a security manager is present and it denies
* {@link RuntimePermission}{@code ("setDefaultUncaughtExceptionHandler")}
*
* @see #setUncaughtExceptionHandler
* @see #getUncaughtExceptionHandler
* @see ThreadGroup#uncaughtException
* @since 1.5
*/
public static void setDefaultUncaughtExceptionHandler(UncaughtExceptionHandler eh) {
@SuppressWarnings("removal")
SecurityManager sm = System.getSecurityManager();
if (sm != null) {
sm.checkPermission(
new RuntimePermission("setDefaultUncaughtExceptionHandler")
);
}
defaultUncaughtExceptionHandler = eh;
}
/**
* Returns the default handler invoked when a thread abruptly terminates
* due to an uncaught exception. If the returned value is {@code null},
* there is no default.
* @since 1.5
* @see #setDefaultUncaughtExceptionHandler
* @return the default uncaught exception handler for all threads
*/
public static UncaughtExceptionHandler getDefaultUncaughtExceptionHandler(){
return defaultUncaughtExceptionHandler;
}
/**
* Returns the handler invoked when this thread abruptly terminates
* due to an uncaught exception. If this thread has not had an
* uncaught exception handler explicitly set then this thread's
* {@code ThreadGroup} object is returned, unless this thread
* has terminated, in which case {@code null} is returned.
* @since 1.5
* @return the uncaught exception handler for this thread
*/
public UncaughtExceptionHandler getUncaughtExceptionHandler() {
return uncaughtExceptionHandler != null ?
uncaughtExceptionHandler : group;
}
/**
* Set the handler invoked when this thread abruptly terminates
* due to an uncaught exception.
*
A thread can take full control of how it responds to uncaught
* exceptions by having its uncaught exception handler explicitly set.
* If no such handler is set then the thread's {@code ThreadGroup}
* object acts as its handler.
* @param eh the object to use as this thread's uncaught exception
* handler. If {@code null} then this thread has no explicit handler.
* @throws SecurityException if the current thread is not allowed to
* modify this thread.
* @see #setDefaultUncaughtExceptionHandler
* @see ThreadGroup#uncaughtException
* @since 1.5
*/
public void setUncaughtExceptionHandler(UncaughtExceptionHandler eh) {
checkAccess();
uncaughtExceptionHandler = eh;
}
/**
* Dispatch an uncaught exception to the handler. This method is
* intended to be called only by the JVM.
*/
private void dispatchUncaughtException(Throwable e) {
getUncaughtExceptionHandler().uncaughtException(this, e);
}
/**
* Removes from the specified map any keys that have been enqueued
* on the specified reference queue.
*/
static void processQueue(ReferenceQueue> queue,
ConcurrentMap>, ?> map)
{
Reference> ref;
while((ref = queue.poll()) != null) {
map.remove(ref);
}
}
/**
* Weak key for Class objects.
**/
static class WeakClassKey extends WeakReference> {
/**
* saved value of the referent's identity hash code, to maintain
* a consistent hash code after the referent has been cleared
*/
private final int hash;
/**
* Create a new WeakClassKey to the given object, registered
* with a queue.
*/
WeakClassKey(Class cl, ReferenceQueue> refQueue) {
super(cl, refQueue);
hash = System.identityHashCode(cl);
}
/**
* Returns the identity hash code of the original referent.
*/
@Override
public int hashCode() {
return hash;
}
/**
* Returns true if the given object is this identical
* WeakClassKey instance, or, if this object's referent has not
* been cleared, if the given object is another WeakClassKey
* instance with the identical non-null referent as this one.
*/
@Override
public boolean equals(Object obj) {
if (obj == this)
return true;
if (obj instanceof WeakClassKey) {
Class referent = get();
return (referent != null) &&
(((WeakClassKey) obj).refersTo(referent));
} else {
return false;
}
}
}
// The following three initially uninitialized fields are exclusively
// managed by class java.util.concurrent.ThreadLocalRandom. These
// fields are used to build the high-performance PRNGs in the
// concurrent code, and we can not risk accidental false sharing.
// Hence, the fields are isolated with @Contended.
/** The current seed for a ThreadLocalRandom */
@jdk.internal.vm.annotation.Contended("tlr")
long threadLocalRandomSeed;
/** Probe hash value; nonzero if threadLocalRandomSeed initialized */
@jdk.internal.vm.annotation.Contended("tlr")
int threadLocalRandomProbe;
/** Secondary seed isolated from public ThreadLocalRandom sequence */
@jdk.internal.vm.annotation.Contended("tlr")
int threadLocalRandomSecondarySeed;
/* Some private helper methods */
private native void setPriority0(int newPriority);
private native void stop0(Object o);
private native void suspend0();
private native void resume0();
private native void interrupt0();
private static native void clearInterruptEvent();
private native void setNativeName(String name);
}