BEGIN LICENSE BLOCK *****
Version: EPL 2.0/GPL 2.0/LGPL 2.1
The contents of this file are subject to the Eclipse Public
License Version 2.0 (the "License"); you may not use this file
except in compliance with the License. You may obtain a copy of
the License at http://www.eclipse.org/legal/epl-v20.html
Software distributed under the License is distributed on an "AS
IS" basis, WITHOUT WARRANTY OF ANY KIND, either express or
implied. See the License for the specific language governing
rights and limitations under the License.
Copyright (C) 2002 Jason Voegele 
Copyright (C) 2002-2004 Anders Bengtsson 
Copyright (C) 2002-2004 Jan Arne Petersen 
Copyright (C) 2004 Thomas E Enebo 
Copyright (C) 2004-2005 Charles O Nutter 
Copyright (C) 2004 Stefan Matthias Aust 
Alternatively, the contents of this file may be used under the terms of
either of the GNU General Public License Version 2 or later (the "GPL"),
or the GNU Lesser General Public License Version 2.1 or later (the "LGPL"),
in which case the provisions of the GPL or the LGPL are applicable instead
of those above. If you wish to allow use of your version of this file only
under the terms of either the GPL or the LGPL, and not to allow others to
use your version of this file under the terms of the EPL, indicate your
decision by deleting the provisions above and replace them with the notice
and other provisions required by the GPL or the LGPL. If you do not delete
the provisions above, a recipient may use your version of this file under
the terms of any one of the EPL, the GPL or the LGPL.
END LICENSE BLOCK /***** BEGIN LICENSE BLOCK *****
 * Version: EPL 2.0/GPL 2.0/LGPL 2.1
 *
 * The contents of this file are subject to the Eclipse Public
 * License Version 2.0 (the "License"); you may not use this file
 * except in compliance with the License. You may obtain a copy of
 * the License at http://www.eclipse.org/legal/epl-v20.html
 *
 * Software distributed under the License is distributed on an "AS
 * IS" basis, WITHOUT WARRANTY OF ANY KIND, either express or
 * implied. See the License for the specific language governing
 * rights and limitations under the License.
 *
 * Copyright (C) 2002 Jason Voegele <jason@jvoegele.com>
 * Copyright (C) 2002-2004 Anders Bengtsson <ndrsbngtssn@yahoo.se>
 * Copyright (C) 2002-2004 Jan Arne Petersen <jpetersen@uni-bonn.de>
 * Copyright (C) 2004 Thomas E Enebo <enebo@acm.org>
 * Copyright (C) 2004-2005 Charles O Nutter <headius@headius.com>
 * Copyright (C) 2004 Stefan Matthias Aust <sma@3plus4.de>
 *
 * Alternatively, the contents of this file may be used under the terms of
 * either of the GNU General Public License Version 2 or later (the "GPL"),
 * or the GNU Lesser General Public License Version 2.1 or later (the "LGPL"),
 * in which case the provisions of the GPL or the LGPL are applicable instead
 * of those above. If you wish to allow use of your version of this file only
 * under the terms of either the GPL or the LGPL, and not to allow others to
 * use your version of this file under the terms of the EPL, indicate your
 * decision by deleting the provisions above and replace them with the notice
 * and other provisions required by the GPL or the LGPL. If you do not delete
 * the provisions above, a recipient may use your version of this file under
 * the terms of any one of the EPL, the GPL or the LGPL.
 ***** END LICENSE BLOCK *****/

package org.jruby;

import java.io.IOException;
import java.lang.ref.WeakReference;
import java.nio.channels.Channel;
import java.nio.channels.SelectableChannel;
import java.nio.channels.SelectionKey;
import java.nio.channels.Selector;
import java.util.Iterator;
import java.util.Queue;
import java.util.Vector;
import java.util.WeakHashMap;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import java.util.Set;
import java.util.concurrent.*;
import java.util.concurrent.atomic.AtomicIntegerFieldUpdater;
import java.util.concurrent.atomic.AtomicReference;
import java.util.concurrent.locks.Condition;
import java.util.concurrent.locks.Lock;

import com.headius.backport9.stack.StackWalker;
import org.jcodings.Encoding;
import org.jruby.anno.JRubyClass;
import org.jruby.anno.JRubyMethod;
import org.jruby.exceptions.RaiseException;
import org.jruby.exceptions.ThreadKill;
import org.jruby.exceptions.Unrescuable;
import org.jruby.ext.thread.Mutex;
import org.jruby.internal.runtime.NativeThread;
import org.jruby.internal.runtime.RubyRunnable;
import org.jruby.internal.runtime.ThreadLike;
import org.jruby.internal.runtime.ThreadService;
import org.jruby.java.proxies.ConcreteJavaProxy;
import org.jruby.javasupport.JavaUtil;
import org.jruby.runtime.Arity;
import org.jruby.runtime.Block;
import org.jruby.runtime.ClassIndex;
import org.jruby.runtime.Helpers;
import org.jruby.runtime.ObjectAllocator;
import org.jruby.runtime.ObjectMarshal;
import org.jruby.runtime.ThreadContext;
import org.jruby.runtime.ExecutionContext;
import org.jruby.runtime.backtrace.FrameType;
import org.jruby.runtime.backtrace.RubyStackTraceElement;
import org.jruby.runtime.builtin.IRubyObject;
import org.jruby.util.ByteList;
import org.jruby.util.StringSupport;
import org.jruby.util.TypeConverter;
import org.jruby.util.io.BlockingIO;
import org.jruby.util.io.ChannelFD;
import org.jruby.util.io.OpenFile;
import org.jruby.util.log.Logger;
import org.jruby.util.log.LoggerFactory;
import org.jruby.common.IRubyWarnings.ID;

import static org.jruby.runtime.Visibility.*;
import static org.jruby.runtime.backtrace.BacktraceData.EMPTY_STACK_TRACE;
import static org.jruby.util.RubyStringBuilder.ids;
import static org.jruby.util.RubyStringBuilder.str;
import static org.jruby.util.RubyStringBuilder.types;

Implementation of Ruby's Thread class.  Each Ruby thread is
mapped to an underlying Java Virtual Machine thread.

Thread encapsulates the behavior of a thread of execution, including the main
thread of the Ruby script.  In the descriptions that follow, the parameter
aSymbol refers to a symbol, which is either a quoted string or a
Symbol (such as :name).
Note: For CVS history, see ThreadClass.java.
/**
 * Implementation of Ruby's <code>Thread</code> class.  Each Ruby thread is
 * mapped to an underlying Java Virtual Machine thread.
 * <p>
 * Thread encapsulates the behavior of a thread of execution, including the main
 * thread of the Ruby script.  In the descriptions that follow, the parameter
 * <code>aSymbol</code> refers to a symbol, which is either a quoted string or a
 * <code>Symbol</code> (such as <code>:name</code>).
 *
 * Note: For CVS history, see ThreadClass.java.
 */
@JRubyClass(name="Thread")
public class RubyThread extends RubyObject implements ExecutionContext {

    private static final Logger LOG = LoggerFactory.getLogger(RubyThread.class);
    // static { LOG.setDebugEnable(true); }

    private static final StackWalker WALKER = ThreadContext.WALKER;

    
The thread-like think that is actually executing /** The thread-like think that is actually executing */
    private volatile ThreadLike threadImpl = ThreadLike.DUMMY;

    
Fiber-local variables /** Fiber-local variables */
    private volatile transient Map<IRubyObject, IRubyObject> fiberLocalVariables;

    
Normal thread-local variables (local to parent thread if in a fiber) /** Normal thread-local variables (local to parent thread if in a fiber) */
    private volatile transient Map<IRubyObject, IRubyObject> threadLocalVariables;

    
Context-local variables, internal-ish thread locals /** Context-local variables, internal-ish thread locals */
    private final Map<Object, IRubyObject> contextVariables = new WeakHashMap<Object, IRubyObject>();

    
Whether this thread should try to abort the program on exception /** Whether this thread should try to abort the program on exception */
    private volatile boolean abortOnException;

    
Whether this thread should report_on_exception when this thread GCs, when it terminates, or never /** Whether this thread should report_on_exception when this thread GCs, when it terminates, or never */
    private volatile IRubyObject reportOnException;

    
The final value resulting from the thread's execution /** The final value resulting from the thread's execution */
    private volatile IRubyObject finalResult;

    private String file; private int line; // Thread.new location (for inspect)

    
The exception currently being raised out of the thread. We reference
it here to continue propagating it while handling thread shutdown
logic and abort_on_exception.
/**
     * The exception currently being raised out of the thread. We reference
     * it here to continue propagating it while handling thread shutdown
     * logic and abort_on_exception.
     */
    private volatile Throwable exitingException;

    
The ThreadGroup to which this thread belongs /** The ThreadGroup to which this thread belongs */
    private volatile RubyThreadGroup threadGroup;

    
Per-thread "current exception" /** Per-thread "current exception" */
    private volatile IRubyObject errorInfo;

    
Weak reference to the ThreadContext for this thread. /** Weak reference to the ThreadContext for this thread. */
    private volatile WeakReference<ThreadContext> contextRef;

    /** Whether to scan for cross-thread events */
    //private volatile boolean handleInterrupt = true;

    
Stack of interrupt masks active for this thread /** Stack of interrupt masks active for this thread */
    private final Vector<RubyHash> interruptMaskStack = new Vector<>(4);

    
Thread-local tuple used for sleeping (semaphore, millis, nanos) /** Thread-local tuple used for sleeping (semaphore, millis, nanos) */
    private final SleepTask2 sleepTask = new SleepTask2();

    public static final int RUBY_MIN_THREAD_PRIORITY = -3;
    public static final int RUBY_MAX_THREAD_PRIORITY = 3;

    
Thread statuses /** Thread statuses */
    public enum Status {
        RUN, SLEEP, ABORTING, DEAD, NATIVE;

        public final ByteList bytes;

        Status() {
            bytes = new ByteList(toString().toLowerCase().getBytes(RubyEncoding.UTF8), false);
        }
    }

    
Current status in an atomic reference /** Current status in an atomic reference */
    private final AtomicReference<Status> status = new AtomicReference<>(Status.RUN);

    
Mail slot for cross-thread events /** Mail slot for cross-thread events */
    private final Queue<IRubyObject> pendingInterruptQueue = new ConcurrentLinkedQueue<>();

    
A function to use to unblock this thread, if possible /** A function to use to unblock this thread, if possible */
    private volatile Unblocker unblockFunc;

    
Argument to pass to the unblocker /** Argument to pass to the unblocker */
    private volatile Object unblockArg;

    
The list of locks this thread currently holds, so they can be released on exit /** The list of locks this thread currently holds, so they can be released on exit */
    private final List<Lock> heldLocks = new Vector<>();

    
Whether or not this thread has been disposed of /** Whether or not this thread has been disposed of */
    private volatile boolean disposed = false;

    
Interrupt flags /** Interrupt flags */
    private volatile int interruptFlag = 0;

    
Interrupt mask to use for disabling certain types /** Interrupt mask to use for disabling certain types */
    private volatile int interruptMask;

    
Short circuit to avoid-re-scanning for interrupts /** Short circuit to avoid-re-scanning for interrupts */
    private volatile boolean pendingInterruptQueueChecked = false;

    private volatile Selector currentSelector;

    private volatile RubyThread fiberCurrentThread;

    private static final AtomicIntegerFieldUpdater<RubyThread> INTERRUPT_FLAG_UPDATER =
            AtomicIntegerFieldUpdater.newUpdater(RubyThread.class, "interruptFlag");

    private static final int TIMER_INTERRUPT_MASK         = 0x01;
    private static final int PENDING_INTERRUPT_MASK       = 0x02;
    private static final int POSTPONED_JOB_INTERRUPT_MASK = 0x04;
    private static final int TRAP_INTERRUPT_MASK	      = 0x08;

    private static final int INTERRUPT_NONE = 0;
    private static final int INTERRUPT_IMMEDIATE = 1;
    private static final int INTERRUPT_ON_BLOCKING = 2;
    private static final int INTERRUPT_NEVER = 3;

    protected RubyThread(Ruby runtime, RubyClass type) {
        super(runtime, type);

        finalResult = errorInfo = runtime.getNil();
        reportOnException = runtime.getReportOnException();
    }

    public RubyThread(Ruby runtime, RubyClass klass, Runnable runnable) {
        this(runtime, klass);

        startThread(runtime.getCurrentContext(), runnable);
    }

    private void executeInterrupts(ThreadContext context, boolean blockingTiming) {
        Ruby runtime = context.runtime;
        int interrupt;

        boolean postponedJobInterrupt = false;

        while ((interrupt = getInterrupts()) != 0) {
            boolean timerInterrupt = (interrupt & TIMER_INTERRUPT_MASK) == TIMER_INTERRUPT_MASK;
            boolean pendingInterrupt = (interrupt & PENDING_INTERRUPT_MASK) == PENDING_INTERRUPT_MASK;

//            if (postponedJobInterrupt) {
//                postponedJobFlush(context);
//            }
            // Missing: signal handling...but perhaps we don't need it on JVM

            if (pendingInterrupt && pendingInterruptActive()) {
                IRubyObject err = pendingInterruptDeque(context, blockingTiming ? INTERRUPT_ON_BLOCKING : INTERRUPT_NONE);

                if (err == UNDEF) {
                    // no error
                } else if (err instanceof RubyFixnum && (((RubyFixnum) err).getLongValue() == 0 ||
                        ((RubyFixnum) err).getLongValue() == 1 ||
                        ((RubyFixnum) err).getLongValue() == 2)) {
                    toKill();
                } else {
                    afterBlockingCall();
                    if (getStatus() == Status.SLEEP) {
                        exitSleep();
                    }
                    // if it's a Ruby exception, force the cause through
                    IRubyObject[] args;
                    if (err instanceof RubyException) {
                        args = Helpers.arrayOf(err, RubyHash.newKwargs(runtime, "cause", ((RubyException) err).cause(context)));
                    } else {
                        args = Helpers.arrayOf(err);
                    }
                    RubyKernel.raise(context, this, args, Block.NULL_BLOCK);
                }
            }

            // Missing: timer interrupt...needed?
        }
    }

    private void postponedJobFlush(ThreadContext context) {
        // unsure if this function has any relevance in JRuby

//        int savedPostponedJobInterruptMask = interruptMask & POSTPONED_JOB_INTERRUPT_MASK;
//
//        errorInfo = context.nil;
//        interruptMask |= POSTPONED_JOB_INTERRUPT_MASK;
    }

    private boolean pendingInterruptActive() {
        if (pendingInterruptQueueChecked) return false;
        if (pendingInterruptQueue.isEmpty()) return false;
        return true;
    }

    private void toKill() {
        pendingInterruptClear();
        status.set(Status.ABORTING);
        throwThreadKill();
    }

    private void pendingInterruptClear() {
        pendingInterruptQueue.clear();
    }

    private int getInterrupts() {
        int interrupt;
        while (true) {
            interrupt = interruptFlag;
            if (INTERRUPT_FLAG_UPDATER.compareAndSet(this, interrupt, interrupt & interruptMask)) {
                break;
            }
        }
        return interrupt & ~interruptMask;
    }

    private IRubyObject pendingInterruptDeque(ThreadContext context, int timing) {
        for (Iterator<IRubyObject> iterator = pendingInterruptQueue.iterator(); iterator.hasNext();) {
            IRubyObject err = iterator.next();
            int maskTiming = pendingInterruptCheckMask(context, err);

            switch (maskTiming) {
                case INTERRUPT_ON_BLOCKING:
                    if (timing != INTERRUPT_ON_BLOCKING) break;
                case INTERRUPT_NONE:
                case INTERRUPT_IMMEDIATE:
                    iterator.remove();
                    return err;
                case INTERRUPT_NEVER:
                    break;
            }
        }

        pendingInterruptQueueChecked = true;

        return UNDEF;
    }

    private int pendingInterruptCheckMask(ThreadContext context, IRubyObject err) {
        int idx = interruptMaskStack.size();
        if (idx == 0) return INTERRUPT_NONE; // fast return

        List<IRubyObject> ancestors = getMetaClass(err).getAncestorList();
        final int ancestorsLen = ancestors.size();

        while (--idx >= 0) {
            RubyHash mask = interruptMaskStack.get(idx);

            for (int j = 0; j < ancestorsLen; j++) {
                IRubyObject klass = ancestors.get(j);
                IRubyObject sym;

                if (!(sym = mask.op_aref(context, klass)).isNil()) {
                    return checkInterruptMask(context, sym);
                }
            }
        }
        return INTERRUPT_NONE;
    }

    public IRubyObject getErrorInfo() {
        return errorInfo;
    }

    public IRubyObject setErrorInfo(IRubyObject errorInfo) {
        this.errorInfo = errorInfo;
        return errorInfo;
    }

    public void setContext(final ThreadContext context) {
        this.contextRef = new WeakReference<>(context);
    }

    public void clearContext() {
        WeakReference<ThreadContext> contextRef = this.contextRef;
        if (contextRef != null) {
            contextRef.clear();
            this.contextRef = null;
        }
    }

    public ThreadContext getContext() {
        WeakReference<ThreadContext> contextRef = this.contextRef;
        return contextRef == null ? null : contextRef.get();
    }

    public Thread getNativeThread() {
        return threadImpl.nativeThread();
    }

    public void setFiberCurrentThread(RubyThread fiberCurrentThread) {
        this.fiberCurrentThread = fiberCurrentThread;
    }

    public RubyThread getFiberCurrentThread() {
        RubyThread fiberCurrentThread = this.fiberCurrentThread;
        return fiberCurrentThread == null ? this : fiberCurrentThread;
    }

    
Perform pre-execution tasks once the native thread is running, but we
have not yet called the Ruby code for the thread.
/**
     * Perform pre-execution tasks once the native thread is running, but we
     * have not yet called the Ruby code for the thread.
     */
    public void beforeStart() {
    }

    
Dispose of the current thread by tidying up connections to other stuff
/**
     * Dispose of the current thread by tidying up connections to other stuff
     */
    public void dispose() {
        if (disposed) return;

        synchronized (this) {
            if (disposed) return;

            disposed = true;

            // remove from parent thread group
            threadGroup.remove(this);

            // unlock all locked locks
            unlockAll();

            // mark thread as DEAD
            beDead();
        }

        // unregister from runtime's ThreadService
        getRuntime().getThreadService().unregisterThread(this);
    }

    public static RubyClass createThreadClass(Ruby runtime) {
        // FIXME: In order for Thread to play well with the standard 'new' behavior,
        // it must provide an allocator that can create empty object instances which
        // initialize then fills with appropriate data.
        RubyClass threadClass = runtime.defineClass("Thread", runtime.getObject(), ObjectAllocator.NOT_ALLOCATABLE_ALLOCATOR);
        runtime.setThread(threadClass);

        threadClass.setClassIndex(ClassIndex.THREAD);
        threadClass.setReifiedClass(RubyThread.class);

        threadClass.defineAnnotatedMethods(RubyThread.class);

        RubyThread rubyThread = new RubyThread(runtime, threadClass);
        // TODO: need to isolate the "current" thread from class creation
        rubyThread.threadImpl = new NativeThread(rubyThread, Thread.currentThread());
        runtime.getThreadService().setMainThread(Thread.currentThread(), rubyThread);

        // set to default thread group
        runtime.getDefaultThreadGroup().addDirectly(rubyThread);

        threadClass.setMarshal(ObjectMarshal.NOT_MARSHALABLE_MARSHAL);

        // set up Thread::Backtrace::Location class
        RubyClass backtrace = threadClass.defineClassUnder("Backtrace", runtime.getObject(), ObjectAllocator.NOT_ALLOCATABLE_ALLOCATOR);
        RubyClass location = backtrace.defineClassUnder("Location", runtime.getObject(), ObjectAllocator.NOT_ALLOCATABLE_ALLOCATOR);

        location.defineAnnotatedMethods(Location.class);

        runtime.setLocation(location);

        return threadClass;
    }

    public static class Location extends RubyObject {
        private final RubyStackTraceElement element;

        private transient RubyString baseLabel = null;
        private transient RubyString label = null;

        public Location(Ruby runtime, RubyClass klass, RubyStackTraceElement element) {
            super(runtime, klass);
            this.element = element;
        }

        @JRubyMethod
        public IRubyObject absolute_path(ThreadContext context) {
            return context.runtime.newString(element.getFileName());
        }

        @JRubyMethod
        public IRubyObject base_label(ThreadContext context) {
            if (baseLabel == null) baseLabel = context.runtime.newString(element.getMethodName());
            return baseLabel;
        }

        @JRubyMethod
        public IRubyObject inspect(ThreadContext context) {
            return to_s(context).inspect();
        }

        @JRubyMethod
        public IRubyObject label(ThreadContext context) {
            if (element.getFrameType() == FrameType.BLOCK) {
                // NOTE: "block in " + ... logic, now, also at RubyStackTraceElement.to_s_mri
                if (label == null) label = context.runtime.newString("block in " + element.getMethodName());
                return label;
            }

            return base_label(context);
        }

        @JRubyMethod
        public IRubyObject lineno(ThreadContext context) {
            return context.runtime.newFixnum(element.getLineNumber());
        }

        @JRubyMethod
        public IRubyObject path(ThreadContext context) {
            return context.runtime.newString(element.getFileName());
        }

        @JRubyMethod
        public IRubyObject to_s(ThreadContext context) {
            return RubyStackTraceElement.to_s_mri(context, element);
        }

        public static RubyArray newLocationArray(Ruby runtime, RubyStackTraceElement[] elements) {
            return newLocationArray(runtime, elements, 0, elements.length);
        }

        public static RubyArray newLocationArray(Ruby runtime, RubyStackTraceElement[] elements,
            final int offset, final int length) {
            final RubyClass locationClass = runtime.getLocation();

            IRubyObject[] ary = new IRubyObject[length];
            for ( int i = 0; i < length; i++ ) {
                ary[i] = new RubyThread.Location(runtime, locationClass, elements[i + offset]);
            }

            return RubyArray.newArrayNoCopy(runtime, ary);
        }

    }

    
Thread.new

Thread.new( [ arg ]* ) {| args | block } -> aThread

Creates a new thread to execute the instructions given in block, and
begins running it. Any arguments passed to Thread.new are passed into the
block.
x = Thread.new { sleep .1; print "x"; print "y"; print "z" }
a = Thread.new { print "a"; print "b"; sleep .2; print "c" }
x.join # Let the threads finish before
a.join # main thread exits...

produces: abxyzc
/**
     * <code>Thread.new</code>
     * <p>
     * Thread.new( <i>[ arg ]*</i> ) {| args | block } -> aThread
     * <p>
     * Creates a new thread to execute the instructions given in block, and
     * begins running it. Any arguments passed to Thread.new are passed into the
     * block.
     * <pre>
     * x = Thread.new { sleep .1; print "x"; print "y"; print "z" }
     * a = Thread.new { print "a"; print "b"; sleep .2; print "c" }
     * x.join # Let the threads finish before
     * a.join # main thread exits...
     * </pre>
     * <i>produces:</i> abxyzc
     */
    @JRubyMethod(name = {"new", "fork"}, rest = true, meta = true)
    public static IRubyObject newInstance(IRubyObject recv, IRubyObject[] args, Block block) {
        return startThread(recv, args, true, block);
    }

    
Basically the same as Thread.new . However, if class Thread is
subclassed, then calling start in that subclass will not invoke the
subclass's initialize method.
/**
     * Basically the same as Thread.new . However, if class Thread is
     * subclassed, then calling start in that subclass will not invoke the
     * subclass's initialize method.
     */
    @JRubyMethod(rest = true, name = "start", meta = true)
    public static RubyThread start(IRubyObject recv, IRubyObject[] args, Block block) {
        // The error message may appear incongruous here, due to the difference
        // between JRuby's Thread model and MRI's.
        // We mimic MRI's message in the name of compatibility.
        if (! block.isGiven()) {
            throw recv.getRuntime().newArgumentError("tried to create Proc object without a block");
        }
        return startThread(recv, args, false, block);
    }

    @Deprecated
    public static RubyThread start19(IRubyObject recv, IRubyObject[] args, Block block) {
        return start(recv, args, block);
    }

    public static RubyThread adopt(IRubyObject recv, Thread t) {
        final Ruby runtime = recv.getRuntime();
        return adoptThread(runtime, runtime.getThreadService(), (RubyClass) recv, t);
    }

    public static RubyThread adopt(Ruby runtime, ThreadService service, Thread thread) {
        return adoptThread(runtime, service, runtime.getThread(), thread);
    }

    private static RubyThread adoptThread(final Ruby runtime, final ThreadService service,
                                          final RubyClass recv, final Thread thread) {
        final RubyThread rubyThread = new RubyThread(runtime, recv);

        rubyThread.threadImpl = new NativeThread(rubyThread, thread);
        ThreadContext context = service.registerNewThread(rubyThread);
        service.associateThread(thread, rubyThread);

        context.preAdoptThread();

        // set to default thread group
        runtime.getDefaultThreadGroup().addDirectly(rubyThread);

        return rubyThread;
    }

    @JRubyMethod(rest = true, visibility = PRIVATE)
    public IRubyObject initialize(ThreadContext context, IRubyObject[] args, Block block) {
        if (!block.isGiven()) throw context.runtime.newThreadError("must be called with a block");
        if (threadImpl != ThreadLike.DUMMY) throw context.runtime.newThreadError("already initialized thread");

        return startThread(context, new RubyRunnable(this, args, block));
    }

    private IRubyObject startThread(ThreadContext context, Runnable runnable) throws RaiseException, OutOfMemoryError {
        final Ruby runtime = context.runtime;
        try {
            Thread thread = new Thread(runnable);
            thread.setDaemon(true);
            this.file = context.getFile();
            this.line = context.getLine();
            initThreadName(runtime, thread, file, line);
            threadImpl = new NativeThread(this, thread);

            addToCorrectThreadGroup(context);

            // JRUBY-2380, associate thread early so it shows up in Thread.list right away, in case it doesn't run immediately
            runtime.getThreadService().associateThread(thread, this);

            // copy parent thread's interrupt masks
            copyInterrupts(context, context.getThread().interruptMaskStack, this.interruptMaskStack);

            threadImpl.start();

            // We yield here to hopefully permit the target thread to schedule
            // MRI immediately schedules it, so this is close but not exact
            Thread.yield();

            return this;
        }
        catch (OutOfMemoryError oome) {
            if ("unable to create new native thread".equals(oome.getMessage())) {
                throw runtime.newThreadError(oome.getMessage());
            }
            throw oome;
        }
        catch (SecurityException ex) {
            throw runtime.newThreadError(ex.getMessage());
        }
    }

    private static final RubyHash[] NULL_ARRAY = new RubyHash[0];

    private static void copyInterrupts(ThreadContext context, Vector<RubyHash> sourceStack, Vector<RubyHash> targetStack) {
        // We do this in a loop so we can use synchronized collections but not deadlock inside addAll.
        // See https://github.com/jruby/jruby/issues/5520
        for (RubyHash h : sourceStack.toArray(NULL_ARRAY)) {
            targetStack.add(h.dupFast(context));
        }
    }

    private static final String RUBY_THREAD_PREFIX = "Ruby-";

    private static void initThreadName(final Ruby runtime, final Thread thread, final String file, final int line) {
        // "Ruby-0-Thread-16: (irb):21"
        final String newName;
        final StringBuilder name = new StringBuilder(24);
        name
                .append(RUBY_THREAD_PREFIX)
                .append(runtime.getRuntimeNumber())
                .append('-')
                .append("Thread-")
                .append(incAndGetThreadCount(runtime));
        if ( file != null ) {
            name
                    .append(':')
                    .append(' ')
                    .append(file)
                    .append(':')
                    .append(line + 1);
        }
        newName = name.toString();

        thread.setName(newName);
    }

    private static long incAndGetThreadCount(final Ruby runtime) {
        return runtime.getThreadService().incrementAndGetThreadCount();
    }

    private static RubyThread startThread(final IRubyObject recv, final IRubyObject[] args, boolean callInit, Block block) {
        Ruby runtime = recv.getRuntime();
        RubyThread rubyThread = new RubyThread(runtime, (RubyClass) recv);

        if (callInit) {
            rubyThread.callInit(args, block);

            if (rubyThread.threadImpl == ThreadLike.DUMMY) {
                throw runtime.newThreadError(str(runtime, "uninitialized thread - check " , types(runtime, (RubyClass) recv), "#initialize"));
            }
        } else {
            // for Thread::start, which does not call the subclass's initialize
            rubyThread.initialize(runtime.getCurrentContext(), args, block);
        }

        return rubyThread;
    }

    protected static RubyThread startWaiterThread(final Ruby runtime, int pid, Block block) {
        final IRubyObject waiter = runtime.getProcess().getConstantAt("Waiter"); // Process::Waiter
        final RubyThread rubyThread = new RubyThread(runtime, (RubyClass) waiter);
        rubyThread.op_aset(runtime.newSymbol("pid"), runtime.newFixnum(pid));
        rubyThread.callInit(IRubyObject.NULL_ARRAY, block);
        return rubyThread;
    }

    public synchronized void cleanTerminate(IRubyObject result) {
        finalResult = result;
    }

    public void beDead() {
        status.set(Status.DEAD);
    }

    public void pollThreadEvents() {
        pollThreadEvents(metaClass.runtime.getCurrentContext());
    }

    // CHECK_INTS
    public void pollThreadEvents(ThreadContext context) {
        if (anyInterrupted()) {
            executeInterrupts(context, true);
        }
    }

    // RUBY_VM_INTERRUPTED_ANY
    private boolean anyInterrupted() {
        return Thread.interrupted() || (interruptFlag & ~interruptMask) != 0;
    }

    private static void throwThreadKill() {
        throw new ThreadKill();
    }

    @JRubyMethod(meta = true)
    public static IRubyObject handle_interrupt(ThreadContext context, IRubyObject self, IRubyObject _mask, Block block) {
        if (!block.isGiven()) {
            throw context.runtime.newArgumentError("block is needed");
        }

        final RubyHash mask = (RubyHash) TypeConverter.convertToType(_mask, context.runtime.getHash(), "to_hash");

        mask.visitAll(context, HandleInterruptVisitor, null);

        final RubyThread thread = context.getThread();
        thread.interruptMaskStack.add(mask);
        if (thread.pendingInterruptQueue.isEmpty()) {
            thread.pendingInterruptQueueChecked = false;
            thread.setInterrupt();
        }

        try {
            // check for any interrupts that should fire with new masks
            thread.pollThreadEvents();

            return block.call(context);
        } finally {
            thread.interruptMaskStack.remove(thread.interruptMaskStack.size() - 1);
            thread.setInterrupt();

            thread.pollThreadEvents(context);
        }
    }

    private static final RubyHash.VisitorWithState HandleInterruptVisitor = new RubyHash.VisitorWithState<Void>() {
        @Override
        public void visit(ThreadContext context, RubyHash self, IRubyObject key, IRubyObject value, int index, Void state) {
            checkInterruptMask(context, value);
        }
    };

    private static int checkInterruptMask(final ThreadContext context, final IRubyObject sym) {
        if (sym instanceof RubySymbol) {
            switch (((RubySymbol) sym).idString()) {
                case "immediate": return INTERRUPT_IMMEDIATE;
                case "on_blocking": return INTERRUPT_ON_BLOCKING;
                case "never": return INTERRUPT_NEVER;
            }
        }
        throw context.runtime.newArgumentError("unknown mask signature");
    }

    @JRubyMethod(name = "pending_interrupt?", meta = true, optional = 1)
    public static IRubyObject pending_interrupt_p(ThreadContext context, IRubyObject self, IRubyObject[] args) {
        return context.getThread().pending_interrupt_p(context, args);
    }

    @JRubyMethod(name = "pending_interrupt?", optional = 1)
    public IRubyObject pending_interrupt_p(ThreadContext context, IRubyObject[] args) {
        if (pendingInterruptQueue.isEmpty()) {
            return context.fals;
        }
        if (args.length == 1) {
            IRubyObject err = args[0];
            if (!(err instanceof RubyModule)) {
                throw context.runtime.newTypeError("class or module required for rescue clause");
            }
            return pendingInterruptInclude((RubyModule) err) ? context.tru : context.fals;
        }
        return context.tru;
    }

    private boolean pendingInterruptInclude(RubyModule err) {
        Iterator<IRubyObject> iterator = pendingInterruptQueue.iterator();
        while (iterator.hasNext()) {
            RubyModule e = (RubyModule) iterator.next();
            if (e.isKindOfModule(err)) return true;
        }
        return false;
    }

    @JRubyMethod(name = "name=", required = 1)
    public IRubyObject setName(IRubyObject name) {
        final Ruby runtime = getRuntime();

        if (!name.isNil()) {
            RubyString nameStr = StringSupport.checkEmbeddedNulls(runtime, name);
            Encoding enc = nameStr.getEncoding();
            if (!enc.isAsciiCompatible()) {
                throw runtime.newArgumentError("ASCII incompatible encoding (" + enc + ")");
            }
            threadImpl.setRubyName(runtime.freezeAndDedupString(nameStr).asJavaString());
        } else {
            threadImpl.setRubyName(null);
        }

        return name;
    }

    @JRubyMethod(name = "name")
    public IRubyObject getName() {
        Ruby runtime = getRuntime();

        CharSequence rubyName = threadImpl.getRubyName();

        if (rubyName == null) return runtime.getNil();

        return RubyString.newString(runtime, rubyName);
    }

    
Returns the status of the global ``abort on exception'' condition. The
default is false. When set to true, will cause all threads to abort (the
process will exit(0)) if an exception is raised in any thread. See also
Thread.abort_on_exception= .
/**
     * Returns the status of the global ``abort on exception'' condition. The
     * default is false. When set to true, will cause all threads to abort (the
     * process will exit(0)) if an exception is raised in any thread. See also
     * Thread.abort_on_exception= .
     */
    @JRubyMethod(name = "abort_on_exception", meta = true)
    public static RubyBoolean abort_on_exception_x(IRubyObject recv) {
        Ruby runtime = recv.getRuntime();
        return runtime.isGlobalAbortOnExceptionEnabled() ? runtime.getTrue() : runtime.getFalse();
    }

    @JRubyMethod(name = "abort_on_exception=", required = 1, meta = true)
    public static IRubyObject abort_on_exception_set_x(IRubyObject recv, IRubyObject value) {
        recv.getRuntime().setGlobalAbortOnExceptionEnabled(value.isTrue());
        return value;
    }

    @JRubyMethod(meta = true)
    public static RubyThread current(IRubyObject recv) {
        return recv.getRuntime().getCurrentContext().getThread();
    }

    @JRubyMethod(meta = true)
    public static RubyThread main(IRubyObject recv) {
        return recv.getRuntime().getThreadService().getMainThread();
    }

    @JRubyMethod(meta = true)
    public static IRubyObject pass(ThreadContext context, IRubyObject recv) {
        Thread.yield();

        return context.nil;
    }

    @JRubyMethod(meta = true)
    public static RubyArray list(IRubyObject recv) {
        Ruby runtime = recv.getRuntime();
        RubyThread[] activeThreads = runtime.getThreadService().getActiveRubyThreads();

        return RubyArray.newArrayMayCopy(runtime, activeThreads);
    }

    private void addToCorrectThreadGroup(ThreadContext context) {
        // JRUBY-3568, inherit threadgroup or use default
        IRubyObject group = context.getThread().group();
        if (!group.isNil()) {
            ((RubyThreadGroup) group).addDirectly(this);
        } else {
            context.runtime.getDefaultThreadGroup().addDirectly(this);
        }
    }

    private RubySymbol getSymbolKey(IRubyObject originalKey) {
        if (originalKey instanceof RubySymbol) return (RubySymbol) originalKey;

        Ruby runtime = getRuntime();

        if (originalKey instanceof RubyString) return runtime.newSymbol(((RubyString) originalKey).getByteList());

        throw runtime.newTypeError(str(runtime, ids(runtime, originalKey), " is not a symbol nor a string"));
    }

    private Map<IRubyObject, IRubyObject> getFiberLocals() {
        Map<IRubyObject, IRubyObject> locals = fiberLocalVariables;
        if (locals == null) {
            synchronized (this) {
                locals = fiberLocalVariables;
                if (locals == null) locals = fiberLocalVariables = new HashMap<>();
            }
        }
        return locals;
    }

    // NOTE: all callers are (expected to be) synchronized
    private Map<IRubyObject, IRubyObject> getThreadLocals() {
        return getFiberCurrentThread().getThreadLocals0();
    }

    private Map<IRubyObject, IRubyObject> getThreadLocals0() {
        Map<IRubyObject, IRubyObject> locals = threadLocalVariables;
        if (locals == null) {
            synchronized (this) {
                locals = threadLocalVariables;
                if (locals == null) locals = threadLocalVariables = new HashMap<>();
            }
        }
        return locals;
    }

    @Override
    public final Map<Object, IRubyObject> getContextVariables() {
        return contextVariables;
    }

    public boolean isAlive(){
        return threadImpl.isAlive() && getStatus() != Status.DEAD;
    }

    @JRubyMethod
    public IRubyObject fetch(ThreadContext context, IRubyObject key, Block block) {
        IRubyObject value = op_aref(context, key);

        if (value.isNil()) {
            if (block.isGiven()) return block.yield(context, key);

            throw context.runtime.newKeyError("key not found: " + key.inspect(), this, key);
        }

        return value;
    }

    @JRubyMethod
    public IRubyObject fetch(ThreadContext context, IRubyObject key, IRubyObject _default, Block block) {
        final boolean blockGiven = block.isGiven();

        if (blockGiven) {
            context.runtime.getWarnings().warn(ID.BLOCK_BEATS_DEFAULT_VALUE, "block supersedes default value argument");
        }

        IRubyObject value = op_aref(context, key);

        if (value == context.nil) {
            if (blockGiven) return block.yield(context, key);
            return _default;
        }

        return value;
    }

    @JRubyMethod(name = "[]", required = 1)
    public IRubyObject op_aref(ThreadContext context, IRubyObject key) {
        key = getSymbolKey(key);
        final Map<IRubyObject, IRubyObject> locals = getFiberLocals();
        synchronized (locals) {
            IRubyObject value;
            return (value = locals.get(key)) == null ? context.nil : value;
        }
    }

    @Deprecated
    public IRubyObject op_aref(IRubyObject key) {
        return op_aref(getRuntime().getCurrentContext(), key);
    }

    @JRubyMethod(name = "[]=", required = 2)
    public IRubyObject op_aset(IRubyObject key, IRubyObject value) {
        checkFrozen();

        key = getSymbolKey(key);
        final Map<IRubyObject, IRubyObject> locals = getFiberLocals();
        synchronized (locals) {
            locals.put(key, value);
        }
        return value;
    }

    @JRubyMethod(name = "key?", required = 1)
    public RubyBoolean key_p(ThreadContext context, IRubyObject key) {
        key = getSymbolKey(key);
        final Map<IRubyObject, IRubyObject> locals = getFiberLocals();
        synchronized (locals) {
            return context.runtime.newBoolean(locals.containsKey(key));
        }
    }

    @Deprecated
    public RubyBoolean key_p(IRubyObject key) {
        return key_p(getRuntime().getCurrentContext(), key);
    }

    @JRubyMethod
    public RubyArray keys() {
        final Map<IRubyObject, IRubyObject> locals = getFiberLocals();
        IRubyObject[] ary;
        synchronized (locals) {
            ary = new IRubyObject[locals.size()];
            int i = 0;
            for (Map.Entry<IRubyObject, IRubyObject> entry : locals.entrySet()) {
                ary[i++] = entry.getKey();
            }
        }
        return RubyArray.newArrayMayCopy(getRuntime(), ary);
    }

    @JRubyMethod(name = "thread_variable?", required = 1)
    public IRubyObject thread_variable_p(ThreadContext context, IRubyObject key) {
        key = getSymbolKey(key);
        final Map<IRubyObject, IRubyObject> locals = getThreadLocals();
        synchronized (locals) {
            return context.runtime.newBoolean(locals.containsKey(key));
        }
    }

    @JRubyMethod(name = "thread_variable_get", required = 1)
    public IRubyObject thread_variable_get(ThreadContext context, IRubyObject key) {
        key = getSymbolKey(key);
        final Map<IRubyObject, IRubyObject> locals = getThreadLocals();
        synchronized (locals) {
            IRubyObject value;
            return (value = locals.get(key)) == null ? context.nil : value;
        }
    }

    @JRubyMethod(name = "thread_variable_set", required = 2)
    public IRubyObject thread_variable_set(ThreadContext context, IRubyObject key, IRubyObject value) {
        checkFrozen();
        key = getSymbolKey(key);
        final Map<IRubyObject, IRubyObject> locals = getThreadLocals();
        synchronized (locals) {
            locals.put(key, value);
        }
        return value;
    }

    @JRubyMethod(name = "thread_variables")
    public IRubyObject thread_variables(ThreadContext context) {
        final Map<IRubyObject, IRubyObject> locals = getThreadLocals();
        IRubyObject[] ary;
        synchronized (locals) {
            ary = new IRubyObject[locals.size()];
            int i = 0;
            for (Map.Entry<IRubyObject, IRubyObject> entry : locals.entrySet()) {
                ary[i++] = entry.getKey();
            }
        }
        return RubyArray.newArrayMayCopy(context.runtime, ary);
    }


    @JRubyMethod
    public RubyBoolean abort_on_exception() {
        return abortOnException ? getRuntime().getTrue() : getRuntime().getFalse();
    }

    @JRubyMethod(name = "abort_on_exception=", required = 1)
    public IRubyObject abort_on_exception_set(IRubyObject val) {
        abortOnException = val.isTrue();
        return val;
    }

    @JRubyMethod(name = "alive?")
    public RubyBoolean alive_p() {
        return isAlive() ? getRuntime().getTrue() : getRuntime().getFalse();
    }

    @Deprecated
    public IRubyObject join(IRubyObject[] args) {
        return join(getRuntime().getCurrentContext(), args);
    }

    @JRubyMethod(optional = 1)
    public IRubyObject join(ThreadContext context, IRubyObject[] args) {
        Ruby runtime = context.runtime;
        long timeoutMillis = Long.MAX_VALUE;

        if (args.length > 0 && !args[0].isNil()) {
            if (args.length > 1) {
                throw runtime.newArgumentError(args.length, 1);
            }
            // MRI behavior: value given in seconds; converted to Float; less
            // than or equal to zero returns immediately; returns nil
            timeoutMillis = (long) (1000 * RubyNumeric.num2dbl(args[0]));
            if (timeoutMillis <= 0) {
            // TODO: not sure that we should skip calling join() altogether.
            // Thread.join() has some implications for Java Memory Model, etc.
                if (threadImpl.isAlive()) {
                    return context.nil;
                } else {
                    return this;
                }
            }
        }

        if (isCurrent()) {
            throw runtime.newThreadError("Target thread must not be current thread");
        }

        RubyThread currentThread = context.getThread();

        try {
            currentThread.enterSleep();

            final long timeToWait = Math.min(timeoutMillis, 200);

            // We need this loop in order to be able to "unblock" the
            // join call without actually calling interrupt.
            long start = System.currentTimeMillis();
            while (true) {
                currentThread.pollThreadEvents(context);
                threadImpl.join(timeToWait);
                if (!threadImpl.isAlive()) {
                    break;
                }
                if (System.currentTimeMillis() - start > timeoutMillis) {
                    break;
                }
            }
        } catch (InterruptedException ie) {
            ie.printStackTrace();
            assert false : ie;
        } catch (ExecutionException ie) {
            ie.printStackTrace();
            assert false : ie;
        } finally {
            currentThread.exitSleep();
        }

        final Throwable exception = this.exitingException;
        if (exception != null) {
            if (exception instanceof RaiseException) {
                // Set $! in the current thread before exiting
                runtime.getGlobalVariables().set("$!", ((RaiseException) exception).getException());
            } else {
                runtime.getGlobalVariables().set("$!", JavaUtil.convertJavaToUsableRubyObject(runtime, exception));
            }
            Helpers.throwException(exception);
        }

        // check events before leaving
        currentThread.pollThreadEvents(context);

        if (threadImpl.isAlive()) {
            return context.nil;
        } else {
            return this;
        }
    }

    @JRubyMethod
    public IRubyObject value(ThreadContext context) {
        join(context, NULL_ARRAY);
        synchronized (this) {
            return finalResult;
        }
    }

    @Deprecated
    public IRubyObject value() {
        return value(getRuntime().getCurrentContext());
    }

    @JRubyMethod
    public IRubyObject group() {
        final RubyThreadGroup group = this.threadGroup;
        return group == null ? getRuntime().getNil() : group;
    }

    void setThreadGroup(RubyThreadGroup rubyThreadGroup) {
        threadGroup = rubyThreadGroup;
    }

    @Override
    public IRubyObject inspect() {
        return inspect(metaClass.runtime.getCurrentContext());
    }

    @JRubyMethod
    public RubyString inspect(ThreadContext context) {
        final Ruby runtime = context.runtime;
        RubyString result = runtime.newString("#<");

        result.cat(getMetaClass().getRealClass().toRubyString(context));
        result.cat(':');
        result.catString(identityString());
        synchronized (this) {
            String id = threadImpl.getRubyName(); // thread.name
            if (notEmpty(id)) {
                result.cat('@');
                result.cat(runtime.newSymbol(id).getBytes());
            }
            if (notEmpty(file) && line >= 0) {
                result.cat('@');
                result.catString(file);
                result.cat(':');
                result.catString(Integer.toString(line + 1));
            }
            result.cat(' ');
            result.catString(status.toString().toLowerCase());
            result.cat('>');
            return result;
        }
    }

    private static boolean notEmpty(String str) {
        return str != null && str.length() > 0;
    }

    @JRubyMethod(meta = true)
    public static IRubyObject stop(ThreadContext context, IRubyObject receiver) {
        RubyThread rubyThread = context.getThread();

        if (context.runtime.getThreadService().getActiveRubyThreads().length == 1) {
            throw context.runtime.newThreadError("stopping only thread\n\tnote: use sleep to stop forever");
        }

        synchronized (rubyThread) {
            rubyThread.pollThreadEvents(context);
            Status oldStatus = rubyThread.getStatus();
            try {
                rubyThread.status.set(Status.SLEEP);
                rubyThread.wait();
            } catch (InterruptedException ie) {
            } finally {
                rubyThread.pollThreadEvents(context);
                rubyThread.status.set(oldStatus);
            }
        }

        return context.nil;
    }

    @JRubyMethod(required = 1, meta = true)
    public static IRubyObject kill(IRubyObject receiver, IRubyObject rubyThread, Block block) {
        if (!(rubyThread instanceof RubyThread)) throw receiver.getRuntime().newTypeError(rubyThread, receiver.getRuntime().getThread());
        return ((RubyThread)rubyThread).kill();
    }

    @JRubyMethod(meta = true)
    public static IRubyObject exit(IRubyObject receiver, Block block) {
        RubyThread rubyThread = receiver.getRuntime().getThreadService().getCurrentContext().getThread();

        return rubyThread.kill();
    }

    @JRubyMethod(name = "stop?")
    public RubyBoolean stop_p() {
        // not valid for "dead" state
        return getRuntime().newBoolean(getStatus() == Status.SLEEP || getStatus() == Status.DEAD);
    }

    @JRubyMethod
    public synchronized RubyThread wakeup() {
        if(!threadImpl.isAlive() && getStatus() == Status.DEAD) {
            throw getRuntime().newThreadError("killed thread");
        }

        status.set(Status.RUN);
        interrupt();

        return this;
    }

    @JRubyMethod
    public RubyFixnum priority() {
        return RubyFixnum.newFixnum(getRuntime(), javaPriorityToRubyPriority(threadImpl.getPriority()));
    }

    @JRubyMethod(name = "priority=", required = 1)
    public IRubyObject priority_set(IRubyObject priority) {
        int iPriority = RubyNumeric.fix2int(priority);

        if (iPriority < RUBY_MIN_THREAD_PRIORITY) {
            iPriority = RUBY_MIN_THREAD_PRIORITY;
        } else if (iPriority > RUBY_MAX_THREAD_PRIORITY) {
            iPriority = RUBY_MAX_THREAD_PRIORITY;
        }

        if (threadImpl.isAlive()) {
            int jPriority = rubyPriorityToJavaPriority(iPriority);
            if (jPriority < Thread.MIN_PRIORITY) {
                jPriority = Thread.MIN_PRIORITY;
            } else if (jPriority > Thread.MAX_PRIORITY) {
                jPriority = Thread.MAX_PRIORITY;
            }
            threadImpl.setPriority(jPriority);
        }

        return RubyFixnum.newFixnum(getRuntime(), iPriority);
    }

    /* helper methods to translate Java thread priority (1-10) to
     * Ruby thread priority (-3 to 3) using a quadratic polynomial ant its
     * inverse passing by (Ruby,Java): (-3,1), (0,5) and (3,10)
     * i.e., j = r^2/18 + 3*r/2 + 5
     *       r = 3/2*sqrt(8*j + 41) - 27/2
     */
    public static int javaPriorityToRubyPriority(int javaPriority) {
        double d = 1.5 * Math.sqrt(8.0 * javaPriority + 41) - 13.5;
        return Math.round((float) d);
    }

    public static int rubyPriorityToJavaPriority(int rubyPriority) {
        double d = (rubyPriority * rubyPriority) / 18.0 + 1.5 * rubyPriority + 5;
        return Math.round((float) d);
    }

    
Simplified utility method for just raising an existing exception in this
thread.
Params:
exception – the exception to raise
Returns:
this thread/**
     * Simplified utility method for just raising an existing exception in this
     * thread.
     *
     * @param exception the exception to raise
     * @return this thread
     */
    public final IRubyObject raise(IRubyObject exception) {
        ThreadContext context = metaClass.runtime.getCurrentContext();
        return genericRaise(context, context.getThread(), exception);
    }

    
Simplified utility method for just raising an existing exception in this
thread.
Params:
exception – the exception to raise
message – the message to use
Returns:
this thread/**
     * Simplified utility method for just raising an existing exception in this
     * thread.
     *
     * @param exception the exception to raise
     * @param message the message to use
     * @return this thread
     */
    public final IRubyObject raise(IRubyObject exception, RubyString message) {
        ThreadContext context = metaClass.runtime.getCurrentContext();
        return genericRaise(context, context.getThread(), exception, message);
    }

    @JRubyMethod(optional = 3)
    public IRubyObject raise(ThreadContext context, IRubyObject[] args, Block block) {
        return genericRaise(context, context.getThread(), args);
    }

    @Deprecated
    public IRubyObject raise(IRubyObject[] args, Block block) {
        return raise(getRuntime().getCurrentContext(), args, block);
    }

    private IRubyObject genericRaise(ThreadContext context, RubyThread currentThread, IRubyObject... args) {
        if (!isAlive()) return context.nil;

        if (currentThread == this) {
            RubyKernel.raise(context, this, args, Block.NULL_BLOCK);
            assert false; // should not reach here
        }

        IRubyObject exception = prepareRaiseException(context, args, Block.NULL_BLOCK);

        pendingInterruptEnqueue(exception);
        interrupt();

        return context.nil;
    }

    private IRubyObject prepareRaiseException(ThreadContext context, IRubyObject[] args, Block block) {
        final Ruby runtime = context.runtime;
        if (args.length == 0) {
            if (errorInfo.isNil()) {
                // We force RaiseException here to populate backtrace
                return RaiseException.from(runtime, runtime.getRuntimeError(), "").getException();
            }
            return errorInfo;
        }

        final IRubyObject arg = args[0];

        IRubyObject tmp;
        final RubyException exception;
        if (args.length == 1) {
            if (arg instanceof RubyString) {
                tmp = runtime.getRuntimeError().newInstance(context, args, block);
            }
            else if (arg instanceof ConcreteJavaProxy ) {
                return arg;
            }
            else if ( ! arg.respondsTo("exception") ) {
                throw runtime.newTypeError("exception class/object expected");
            } else {
                tmp = arg.callMethod(context, "exception");
            }
        } else {
            if ( ! arg.respondsTo("exception") ) {
                throw runtime.newTypeError("exception class/object expected");
            }

            tmp = arg.callMethod(context, "exception", args[1]);
        }

        if (!runtime.getException().isInstance(tmp)) {
            throw runtime.newTypeError("exception object expected");
        }

        exception = (RubyException) tmp;

        if (args.length == 3) {
            exception.set_backtrace(args[2]);
        }

        IRubyObject cause = context.getErrorInfo();
        if (cause != exception) {
            exception.setCause(cause);
        }

        return exception;
    }

    @JRubyMethod
    public synchronized IRubyObject run() {
        return wakeup();
    }

    
Sleep the current thread for millis, waking up on any thread interrupts.
We can never be sure if a wait will finish because of a Java "spurious wakeup".  So if we
explicitly wakeup and we wait less than requested amount we will return false.  We will
return true if we sleep right amount or less than right amount via spurious wakeup.
Params:
millis – Number of milliseconds to sleep. Zero sleeps forever./**
     * Sleep the current thread for millis, waking up on any thread interrupts.
     *
     * We can never be sure if a wait will finish because of a Java "spurious wakeup".  So if we
     * explicitly wakeup and we wait less than requested amount we will return false.  We will
     * return true if we sleep right amount or less than right amount via spurious wakeup.
     *
     * @param millis Number of milliseconds to sleep. Zero sleeps forever.
     */
    public boolean sleep(long millis) throws InterruptedException {
        assert this == getRuntime().getCurrentContext().getThread();
        sleepTask.millis = millis;
        try {
            long timeSlept = executeTask(getContext(), null, sleepTask);
            if (millis == 0 || timeSlept >= millis) {
                // sleep was unbounded or we slept long enough
                return true;
            } else {
                // sleep was bounded and we did not sleep long enough
                return false;
            }
        } finally {
            // ensure we've re-acquired the semaphore, or a subsequent sleep may return immediately
            sleepTask.semaphore.drainPermits();
        }
    }

    public IRubyObject status() { // not used
        return status(getRuntime().getCurrentContext());
    }

    @JRubyMethod
    public IRubyObject status(ThreadContext context) {
        final Status status = getStatus();
        if (threadImpl.isAlive() && status != Status.DEAD) { // isAlive()
            return context.runtime.getThreadStatus(status);
        }

        return exitingException != null ? context.nil : context.fals;
    }

    @Deprecated
    public static interface BlockingTask {
        public void run() throws InterruptedException;
        public void wakeup();
    }

    public interface Unblocker<Data> {
        public void wakeup(RubyThread thread, Data self);
    }

    public interface Task<Data, Return> extends Unblocker<Data> {
        public Return run(ThreadContext context, Data data) throws InterruptedException;
        public void wakeup(RubyThread thread, Data data);
    }

    public static final class SleepTask implements BlockingTask {
        private final Object object;
        private final long millis;
        private final int nanos;

        public SleepTask(Object object, long millis, int nanos) {
            this.object = object;
            this.millis = millis;
            this.nanos = nanos;
        }

        @Override
        public void run() throws InterruptedException {
            synchronized (object) {
                object.wait(millis, nanos);
            }
        }

        @Override
        public void wakeup() {
            synchronized (object) {
                object.notify();
            }
        }
    }

    
A Task for sleeping.
The Semaphore is immediately drained on construction, so that any subsequent acquire will block.
The sleep is interrupted by releasing a permit. All permits are drained again on exit to ensure
the next sleep blocks.
/**
     * A Task for sleeping.
     *
     * The Semaphore is immediately drained on construction, so that any subsequent acquire will block.
     * The sleep is interrupted by releasing a permit. All permits are drained again on exit to ensure
     * the next sleep blocks.
     */
    private static class SleepTask2 implements Task<Object, Long> {
        final Semaphore semaphore = new Semaphore(1);
        long millis;
        {semaphore.drainPermits();}

        @Override
        public Long run(ThreadContext context, Object data) throws InterruptedException {
            long start = System.currentTimeMillis();

            try {
                if (millis == 0) {
                    semaphore.tryAcquire(Long.MAX_VALUE, TimeUnit.MILLISECONDS);
                } else {
                    semaphore.tryAcquire(millis, TimeUnit.MILLISECONDS);
                }

                return System.currentTimeMillis() - start;
            } finally {
                semaphore.drainPermits();
            }
        }

        @Override
        public void wakeup(RubyThread thread, Object data) {
            semaphore.release();
        }
    }

    @Deprecated
    public void executeBlockingTask(BlockingTask task) throws InterruptedException {
        try {
            this.currentBlockingTask = task;
            enterSleep();
            pollThreadEvents();
            task.run();
        } finally {
            exitSleep();
            currentBlockingTask = null;
            pollThreadEvents();
        }
    }

    public <Data, Return> Return executeTask(ThreadContext context, Data data, Task<Data, Return> task) throws InterruptedException {
        return executeTask(context, data, Status.SLEEP, task);
    }

    public <Data, Return> Return executeTask(ThreadContext context, Data data, Status status, Task<Data, Return> task) throws InterruptedException {
        Status oldStatus = this.status.get();
        try {
            this.unblockArg = data;
            this.unblockFunc = task;

            // check for interrupt before going into blocking call
            pollThreadEvents(context);

            this.status.set(status);

            return task.run(context, data);
        } finally {
            this.status.set(oldStatus);
            this.unblockFunc = null;
            this.unblockArg = null;
            pollThreadEvents(context);
        }
    }

    public void enterSleep() {
        status.set(Status.SLEEP);
    }

    public void exitSleep() {
        if (getStatus() != Status.ABORTING) {
            status.set(Status.RUN);
        }
    }

    private Status getStatus() {
        Status status = this.status.get();

        if (status != Status.NATIVE) return status;

        return nativeStatus();
    }

    private Status nativeStatus() {
        switch (getNativeThread().getState()) {
            case NEW:
            case RUNNABLE:
            default:
                return Status.RUN;
            case BLOCKED:
            case WAITING:
            case TIMED_WAITING:
                return Status.SLEEP;
            case TERMINATED:
                return Status.DEAD;
        }
    }

    @JRubyMethod(name = {"kill", "exit", "terminate"})
    public IRubyObject kill() {
        Ruby runtime = getRuntime();
        // need to reexamine this
        RubyThread currentThread = runtime.getCurrentContext().getThread();

        if (currentThread == runtime.getThreadService().getMainThread()) {
            // rb_exit to hard exit process...not quite right for us
        }

        status.set(Status.ABORTING);

        return genericKill(runtime, currentThread);
    }

    private IRubyObject genericKill(Ruby runtime, RubyThread currentThread) {
        // If the killee thread is the same as the killer thread, just die
        if (currentThread == this) throwThreadKill();

        pendingInterruptEnqueue(RubyFixnum.zero(runtime));
        interrupt();

        return this;
    }

    private void pendingInterruptEnqueue(IRubyObject v) {
        pendingInterruptQueue.add(v);
        pendingInterruptQueueChecked = false;
    }

    
Used for finalizers that need to kill a Ruby thread. Finalizers run in
a VM thread to which we do not want to attach a ThreadContext and within
which we do not want to check for Ruby thread events. This mechanism goes
directly to mail delivery, bypassing all Ruby Thread-related steps.
/**
     * Used for finalizers that need to kill a Ruby thread. Finalizers run in
     * a VM thread to which we do not want to attach a ThreadContext and within
     * which we do not want to check for Ruby thread events. This mechanism goes
     * directly to mail delivery, bypassing all Ruby Thread-related steps.
     */
    public void dieFromFinalizer() {
        genericKill(getRuntime(), null);
    }

    //private static void debug(RubyThread thread, String message) {
    //    if (LOG.isDebugEnabled()) LOG.debug( "{} ({}): {}", Thread.currentThread(), thread.status, message );
    //}

    @JRubyMethod
    public IRubyObject safe_level() {
        throw getRuntime().newNotImplementedError("Thread-specific SAFE levels are not supported");
    }

    @JRubyMethod(name = "backtrace")
    public IRubyObject backtrace(ThreadContext context) {
        return backtraceInternal(context, null, null);
    }

    @JRubyMethod(name = "backtrace")
    public IRubyObject backtrace(ThreadContext context, IRubyObject level) {
        return backtraceInternal(context, level, null);
    }

    @JRubyMethod(name = "backtrace")
    public IRubyObject backtrace(ThreadContext context, IRubyObject level, IRubyObject length) {
        return backtraceInternal(context, level, length);
    }

    private IRubyObject backtraceInternal(ThreadContext callerContext, IRubyObject level, IRubyObject length) {
        ThreadContext context = getContext();
        Thread nativeThread = getNativeThread();

        // context can be nil if we have not started or GC has claimed our context
        // nativeThread can be null if the thread has terminated and GC has claimed it
        // nativeThread may have finished
        if (context == null || nativeThread == null || !nativeThread.isAlive()) return callerContext.nil;

        return RubyKernel.withLevelAndLength(
                context, level, length, 0,
                (ctx, lev, len) -> WALKER.walk(getNativeThread().getStackTrace(), stream -> ctx.createCallerBacktrace(lev, len, stream)));
    }

    @JRubyMethod
    public IRubyObject backtrace_locations(ThreadContext context) {
        return backtraceLocationsInternal(context, null, null);
    }

    @JRubyMethod
    public IRubyObject backtrace_locations(ThreadContext context, IRubyObject level) {
        return backtraceLocationsInternal(context, level, null);
    }

    @JRubyMethod
    public IRubyObject backtrace_locations(ThreadContext context, IRubyObject level, IRubyObject length) {
        return backtraceLocationsInternal(context, level, length);
    }

    private IRubyObject backtraceLocationsInternal(ThreadContext callerContext, IRubyObject level, IRubyObject length) {
        ThreadContext context = getContext();
        Thread nativeThread = getNativeThread();

        // context can be nil if we have not started or GC has claimed our context
        // nativeThread can be null if the thread has terminated and GC has claimed it
        // nativeThread may have finished
        if (context == null || nativeThread == null || !nativeThread.isAlive()) return callerContext.nil;

        return RubyKernel.withLevelAndLength(
                context, level, length, 0,
                (ctx, lev, len) -> WALKER.walk(getNativeThread().getStackTrace(), stream -> ctx.createCallerLocations(lev, len, stream)));
    }

    @JRubyMethod(name = "report_on_exception=")
    public IRubyObject report_on_exception_set(ThreadContext context, IRubyObject state) {
        if (state.isNil()) {
            reportOnException = state;
        } else {
            reportOnException = state.isTrue() ? context.tru : context.fals;
        }
        return this;
    }

    @JRubyMethod(name = "report_on_exception")
    public IRubyObject report_on_exception(ThreadContext context) {
        return reportOnException;
    }

    @JRubyMethod(name = "report_on_exception=", meta = true)
    public static IRubyObject report_on_exception_set(ThreadContext context, IRubyObject self, IRubyObject state) {
        Ruby runtime = context.runtime;
        
        if (state.isNil()) {
            runtime.setReportOnException(state);
        } else {
            runtime.setReportOnException(runtime.newBoolean(state.isTrue()));
        }

        return self;
    }

    @JRubyMethod(name = "report_on_exception", meta = true)
    public static IRubyObject report_on_exception(ThreadContext context, IRubyObject self) {
        return context.runtime.getReportOnException();
    }

    public StackTraceElement[] javaBacktrace() {
        if (threadImpl instanceof NativeThread) {
            return ((NativeThread)threadImpl).getThread().getStackTrace();
        }

        // Future-based threads can't get a Java trace
        return EMPTY_STACK_TRACE;
    }

    private boolean isCurrent() {
        return threadImpl.isCurrent();
    }

    public void exceptionRaised(RaiseException exception) {
        exceptionRaised((Throwable) exception);
    }

    protected void printReportExceptionWarning() {
        Ruby runtime = getRuntime();
        String name = threadImpl.getReportName();
        runtime.getErrorStream().println("warning: thread \"" + name + "\" terminated with exception (report_on_exception is true):");
    }

    
For handling all exceptions bubbling out of threads
Params:
throwable – /**
     * For handling all exceptions bubbling out of threads
     * @param throwable
     */
    public void exceptionRaised(Throwable throwable) {
        // if unrescuable (internal exceptions) just re-raise and let it be handled by thread handler
        if (throwable instanceof Unrescuable) {
            Helpers.throwException(throwable);
        }

        final Ruby runtime = getRuntime();

        assert isCurrent();

        IRubyObject rubyException;

        if (throwable instanceof RaiseException) {
            RaiseException exception = (RaiseException) throwable;
            rubyException = exception.getException();
        } else {
            rubyException = JavaUtil.convertJavaToUsableRubyObject(runtime, throwable);
        }

        boolean report;
        if (runtime.getSystemExit().isInstance(rubyException)) {
            runtime.getThreadService().getMainThread().raise(rubyException);
        } else if ((report = reportOnException.isTrue()) || abortOnException(runtime)) {
            if (report) {
                printReportExceptionWarning();
                runtime.printError(throwable);
            }
            if (abortOnException(runtime)) {
                runtime.getThreadService().getMainThread().raise(rubyException);
            }
        } else if (runtime.isDebug()) {
            runtime.printError(throwable);
        }

        exitingException = throwable;
    }

    private boolean abortOnException(Ruby runtime) {
        return (runtime.isGlobalAbortOnExceptionEnabled() || abortOnException);
    }

    public static RubyThread mainThread(IRubyObject receiver) {
        return receiver.getRuntime().getThreadService().getMainThread();
    }

    
Perform an interruptible select operation on the given channel and fptr,
waiting for the requested operations or the given timeout.
Params:
io – the RubyIO that contains the channel, for managing blocked threads list.
ops – the operations to wait for, from {@see java.nio.channels.SelectionKey}.
Returns:
true if the IO's channel became ready for the requested operations, false if
        it was not selectable./**
     * Perform an interruptible select operation on the given channel and fptr,
     * waiting for the requested operations or the given timeout.
     *
     * @param io the RubyIO that contains the channel, for managing blocked threads list.
     * @param ops the operations to wait for, from {@see java.nio.channels.SelectionKey}.
     * @return true if the IO's channel became ready for the requested operations, false if
     *         it was not selectable.
     */
    public boolean select(RubyIO io, int ops) {
        return select(io.getChannel(), io.getOpenFile(), ops);
    }

    
Perform an interruptible select operation on the given channel and fptr,
waiting for the requested operations or the given timeout.
Params:
io – the RubyIO that contains the channel, for managing blocked threads list.
ops – the operations to wait for, from {@see java.nio.channels.SelectionKey}.
timeout – a timeout in ms to limit the select. Less than zero selects forever,
               zero selects and returns ready channels or nothing immediately, and
               greater than zero selects for at most that many ms.
Returns:
true if the IO's channel became ready for the requested operations, false if
        it timed out or was not selectable./**
     * Perform an interruptible select operation on the given channel and fptr,
     * waiting for the requested operations or the given timeout.
     *
     * @param io the RubyIO that contains the channel, for managing blocked threads list.
     * @param ops the operations to wait for, from {@see java.nio.channels.SelectionKey}.
     * @param timeout a timeout in ms to limit the select. Less than zero selects forever,
     *                zero selects and returns ready channels or nothing immediately, and
     *                greater than zero selects for at most that many ms.
     * @return true if the IO's channel became ready for the requested operations, false if
     *         it timed out or was not selectable.
     */
    public boolean select(RubyIO io, int ops, long timeout) {
        return select(io.getChannel(), io.getOpenFile(), ops, timeout);
    }

    
Perform an interruptible select operation on the given channel and fptr,
waiting for the requested operations.
Params:
channel – the channel to perform a select against. If this is not
               a selectable channel, then this method will just return true.
fptr – the fptr that contains the channel, for managing blocked threads list.
ops – the operations to wait for, from {@see java.nio.channels.SelectionKey}.
Returns:
true if the channel became ready for the requested operations, false if
        it was not selectable./**
     * Perform an interruptible select operation on the given channel and fptr,
     * waiting for the requested operations.
     *
     * @param channel the channel to perform a select against. If this is not
     *                a selectable channel, then this method will just return true.
     * @param fptr the fptr that contains the channel, for managing blocked threads list.
     * @param ops the operations to wait for, from {@see java.nio.channels.SelectionKey}.
     * @return true if the channel became ready for the requested operations, false if
     *         it was not selectable.
     */
    public boolean select(Channel channel, OpenFile fptr, int ops) {
        return select(channel, fptr, ops, -1);
    }

    
Perform an interruptible select operation on the given channel and fptr,
waiting for the requested operations.
Params:
channel – the channel to perform a select against. If this is not
               a selectable channel, then this method will just return true.
io – the RubyIO that contains the channel, for managing blocked threads list.
ops – the operations to wait for, from {@see java.nio.channels.SelectionKey}.
Returns:
true if the channel became ready for the requested operations, false if
        it was not selectable./**
     * Perform an interruptible select operation on the given channel and fptr,
     * waiting for the requested operations.
     *
     * @param channel the channel to perform a select against. If this is not
     *                a selectable channel, then this method will just return true.
     * @param io the RubyIO that contains the channel, for managing blocked threads list.
     * @param ops the operations to wait for, from {@see java.nio.channels.SelectionKey}.
     * @return true if the channel became ready for the requested operations, false if
     *         it was not selectable.
     */
    public boolean select(Channel channel, RubyIO io, int ops) {
        return select(channel, io == null ? null : io.getOpenFile(), ops, -1);
    }

    
Perform an interruptible select operation on the given channel and fptr,
waiting for the requested operations or the given timeout.
Params:
channel – the channel to perform a select against. If this is not
               a selectable channel, then this method will just return true.
io – the RubyIO that contains the channel, for managing blocked threads list.
ops – the operations to wait for, from {@see java.nio.channels.SelectionKey}.
timeout – a timeout in ms to limit the select. Less than zero selects forever,
               zero selects and returns ready channels or nothing immediately, and
               greater than zero selects for at most that many ms.
Returns:
true if the channel became ready for the requested operations, false if
        it timed out or was not selectable./**
     * Perform an interruptible select operation on the given channel and fptr,
     * waiting for the requested operations or the given timeout.
     *
     * @param channel the channel to perform a select against. If this is not
     *                a selectable channel, then this method will just return true.
     * @param io the RubyIO that contains the channel, for managing blocked threads list.
     * @param ops the operations to wait for, from {@see java.nio.channels.SelectionKey}.
     * @param timeout a timeout in ms to limit the select. Less than zero selects forever,
     *                zero selects and returns ready channels or nothing immediately, and
     *                greater than zero selects for at most that many ms.
     * @return true if the channel became ready for the requested operations, false if
     *         it timed out or was not selectable.
     */
    public boolean select(Channel channel, RubyIO io, int ops, long timeout) {
        return select(channel, io == null ? null : io.getOpenFile(), ops, timeout);
    }

    
Perform an interruptible select operation on the given channel and fptr,
waiting for the requested operations or the given timeout.
Params:
channel – the channel to perform a select against. If this is not
               a selectable channel, then this method will just return true.
fptr – the fptr that contains the channel, for managing blocked threads list.
ops – the operations to wait for, from {@see java.nio.channels.SelectionKey}.
timeout – a timeout in ms to limit the select. Less than zero selects forever,
               zero selects and returns ready channels or nothing immediately, and
               greater than zero selects for at most that many ms.
Returns:
true if the channel became ready for the requested operations, false if
        it timed out or was not selectable./**
     * Perform an interruptible select operation on the given channel and fptr,
     * waiting for the requested operations or the given timeout.
     *
     * @param channel the channel to perform a select against. If this is not
     *                a selectable channel, then this method will just return true.
     * @param fptr the fptr that contains the channel, for managing blocked threads list.
     * @param ops the operations to wait for, from {@see java.nio.channels.SelectionKey}.
     * @param timeout a timeout in ms to limit the select. Less than zero selects forever,
     *                zero selects and returns ready channels or nothing immediately, and
     *                greater than zero selects for at most that many ms.
     * @return true if the channel became ready for the requested operations, false if
     *         it timed out or was not selectable.
     */
    public boolean select(Channel channel, OpenFile fptr, int ops, long timeout) {
        // Use selectables but only if they're not associated with a file (which has odd select semantics)
        ChannelFD fd = fptr == null ? null : fptr.fd();
        if (channel instanceof SelectableChannel && fd != null) {
            SelectableChannel selectable = (SelectableChannel)channel;

            // ensure we have fptr locked, but release it to avoid deadlock
            boolean locked = false;
            if (fptr != null) {
                locked = fptr.lock();
                fptr.unlock();
            }
            try {
                synchronized (selectable.blockingLock()) {
                    boolean oldBlocking = selectable.isBlocking();

                    SelectionKey key;
                    try {
                        selectable.configureBlocking(false);

                        if (fptr != null) fptr.addBlockingThread(this);
                        currentSelector = getRuntime().getSelectorPool().get(selectable.provider());

                        key = selectable.register(currentSelector, ops);

                        beforeBlockingCall();
                        int result;

                        if (timeout < 0) {
                            result = currentSelector.select();
                        } else if (timeout == 0) {
                            result = currentSelector.selectNow();
                        } else {
                            result = currentSelector.select(timeout);
                        }

                        // check for thread events, in case we've been woken up to die
                        pollThreadEvents();

                        if (result == 1) {
                            Set<SelectionKey> keySet = currentSelector.selectedKeys();

                            if (keySet.iterator().next() == key) {
                                return true;
                            }
                        }

                        return false;
                    } catch (IOException ioe) {
                        throw getRuntime().newIOErrorFromException(ioe);
                    } finally {
                        // Note: I don't like ignoring these exceptions, but it's
                        // unclear how likely they are to happen or what damage we
                        // might do by ignoring them. Note that the pieces are separate
                        // so that we can ensure one failing does not affect the others
                        // running.

                        // shut down and null out the selector
                        try {
                            if (currentSelector != null) {
                                getRuntime().getSelectorPool().put(currentSelector);
                            }
                        } catch (Exception e) {
                            // ignore
                        } finally {
                            currentSelector = null;
                        }

                        // remove this thread as a blocker against the given IO
                        if (fptr != null) fptr.removeBlockingThread(this);

                        // go back to previous blocking state on the selectable
                        try {
                            selectable.configureBlocking(oldBlocking);
                        } catch (Exception e) {
                            // ignore
                        }

                        // clear thread state from blocking call
                        afterBlockingCall();
                    }
                }
            } finally {
                if (fptr != null) {
                    fptr.lock();
                    if (locked) fptr.unlock();
                }
            }
        } else {
            // can't select, just have to do a blocking call
            return true;
        }
    }

    @SuppressWarnings("deprecated")
    public synchronized void interrupt() {
        setInterrupt();

        Selector activeSelector = currentSelector;
        if (activeSelector != null) {
            activeSelector.wakeup();
        }
        BlockingIO.Condition iowait = blockingIO;
        if (iowait != null) {
            iowait.cancel();
        }

        Unblocker task = this.unblockFunc;
        if (task != null) {
            task.wakeup(this, unblockArg);
        }

        // deprecated
        {
            BlockingTask t = currentBlockingTask;
            if (t != null) {
                t.wakeup();
            }
        }

        // If this thread is sleeping or stopped, wake it
        notify();
    }

    public void setInterrupt() {
        while (true) {
            int oldFlag = interruptFlag;
            if (INTERRUPT_FLAG_UPDATER.compareAndSet(this, oldFlag, oldFlag | PENDING_INTERRUPT_MASK)) {
                return;
            }
        }
    }

    private volatile BlockingIO.Condition blockingIO = null;
    public boolean waitForIO(ThreadContext context, RubyIO io, int ops) {
        Channel channel = io.getChannel();

        if (!(channel instanceof SelectableChannel)) {
            return true;
        }
        try {
            io.addBlockingThread(this);
            blockingIO = BlockingIO.newCondition(channel, ops);
            boolean ready = blockingIO.await();

            // check for thread events, in case we've been woken up to die
            pollThreadEvents(context);
            return ready;
        } catch (IOException ioe) {
            throw context.runtime.newRuntimeError("Error with selector: " + ioe);
        } catch (InterruptedException ex) {
            // FIXME: not correct exception
            throw context.runtime.newRuntimeError("Interrupted");
        } finally {
            blockingIO = null;
            io.removeBlockingThread(this);
        }
    }
    public void beforeBlockingCall() {
        pollThreadEvents();
        enterSleep();
    }

    public void afterBlockingCall() {
        exitSleep();
        pollThreadEvents();
    }

    public boolean wait_timeout(IRubyObject o, Double timeout) throws InterruptedException {
        if ( timeout != null ) {
            long delay_ns = (long)(timeout.doubleValue() * 1000000000.0);
            long start_ns = System.nanoTime();
            if (delay_ns > 0) {
                long delay_ms = delay_ns / 1000000;
                int delay_ns_remainder = (int)( delay_ns % 1000000 );
                executeBlockingTask(new SleepTask(o, delay_ms, delay_ns_remainder));
            }
            long end_ns = System.nanoTime();
            return ( end_ns - start_ns ) <= delay_ns;
        } else {
            executeBlockingTask(new SleepTask(o, 0, 0));
            return true;
        }
    }

    public RubyThreadGroup getThreadGroup() {
        return threadGroup;
    }

    @Override
    public boolean equals(Object obj) {
        if (obj == null) {
            return false;
        }
        if (getClass() != obj.getClass()) {
            return false;
        }
        final RubyThread other = (RubyThread)obj;
        if (this.threadImpl != other.threadImpl && (this.threadImpl == ThreadLike.DUMMY || !this.threadImpl.equals(other.threadImpl))) {
            return false;
        }
        return true;
    }

    @Override
    public int hashCode() {
        return 97 * (3 + (this.threadImpl != ThreadLike.DUMMY ? this.threadImpl.hashCode() : 0));
    }

    @Override
    public String toString() {
        return threadImpl.toString();
    }

    
Acquire the given lock, holding a reference to it for cleanup on thread
termination.
Params:
lock – the lock to acquire, released on thread termination/**
     * Acquire the given lock, holding a reference to it for cleanup on thread
     * termination.
     *
     * @param lock the lock to acquire, released on thread termination
     */
    public void lock(Lock lock) {
        assert Thread.currentThread() == getNativeThread();
        lock.lock();
        heldLocks.add(lock);
    }

    
Acquire the given lock interruptibly, holding a reference to it for cleanup
on thread termination.
Params:
lock – the lock to acquire, released on thread termination
Throws:
InterruptedException – if the lock acquisition is interrupted/**
     * Acquire the given lock interruptibly, holding a reference to it for cleanup
     * on thread termination.
     *
     * @param lock the lock to acquire, released on thread termination
     * @throws InterruptedException if the lock acquisition is interrupted
     */
    public void lockInterruptibly(Lock lock) throws InterruptedException {
        assert Thread.currentThread() == getNativeThread();
        executeTask(getContext(), lock, new RubyThread.Task<Lock, Object>() {
            @Override
            public Object run(ThreadContext context, Lock reentrantLock) throws InterruptedException {
                reentrantLock.lockInterruptibly();
                return reentrantLock;
            }

            @Override
            public void wakeup(RubyThread thread, Lock reentrantLock) {
                thread.getNativeThread().interrupt();
            }
        });
        heldLocks.add(lock);
    }

    
Try to acquire the given lock, adding it to a list of held locks for cleanup
on thread termination if it is acquired. Return immediately if the lock
cannot be acquired.
Params:
lock – the lock to acquire, released on thread termination/**
     * Try to acquire the given lock, adding it to a list of held locks for cleanup
     * on thread termination if it is acquired. Return immediately if the lock
     * cannot be acquired.
     *
     * @param lock the lock to acquire, released on thread termination
     */
    public boolean tryLock(Lock lock) {
        assert Thread.currentThread() == getNativeThread();
        boolean locked = lock.tryLock();
        if (locked) {
            heldLocks.add(lock);
        }
        return locked;
    }

    
Release the given lock and remove it from the list of locks to be released
on thread termination.
Params:
lock – the lock to release and dereferences/**
     * Release the given lock and remove it from the list of locks to be released
     * on thread termination.
     *
     * @param lock the lock to release and dereferences
     */
    public void unlock(Lock lock) {
        assert Thread.currentThread() == getNativeThread();
        lock.unlock();
        heldLocks.remove(lock);
    }

    
Release all locks held.
/**
     * Release all locks held.
     */
    public void unlockAll() {
        assert Thread.currentThread() == getNativeThread();
        for (Lock lock : heldLocks) {
            lock.unlock();
        }
    }

    
Release lock and sleep.
/**
     * Release lock and sleep.
     */
    public void sleep(Lock lock) throws InterruptedException {
        sleep(lock, 0);
    }

    
Release lock and sleep for the specified number of milliseconds.
/**
     * Release lock and sleep for the specified number of milliseconds.
     */
    public void sleep(Lock lock, long millis) throws InterruptedException {
        assert Thread.currentThread() == getNativeThread();
        executeTask(getContext(), lock.newCondition(), Status.NATIVE, new Task<Condition, Object>() {
            @Override
            public Object run(ThreadContext context, Condition condition) throws InterruptedException {
                if (millis == 0) {
                    condition.await();
                } else {
                    condition.await(millis, TimeUnit.MILLISECONDS);
                }
                return null;
            }

            @Override
            public void wakeup(RubyThread thread, Condition condition) {
                thread.getNativeThread().interrupt();
            }
        });
    }

    private String identityString() {
        return "0x" + Integer.toHexString(System.identityHashCode(this));
    }

    private static final String MUTEX_FOR_THREAD_EXCLUSIVE = "MUTEX_FOR_THREAD_EXCLUSIVE";

    @Deprecated // Thread.exclusive(&block)
    @JRubyMethod(meta = true)
    public static IRubyObject exclusive(ThreadContext context, IRubyObject recv, Block block) {
        recv.callMethod(context, "warn", context.runtime.newString("Thread.exclusive is deprecated, use Thread::Mutex"));
        return getMutexForThreadExclusive(context, (RubyClass) recv).synchronize(context, block);
    }

    private static Mutex getMutexForThreadExclusive(ThreadContext context, RubyClass recv) {
        Mutex mutex = (Mutex) recv.getConstantNoConstMissing(MUTEX_FOR_THREAD_EXCLUSIVE, false, false);
        if (mutex != null) return mutex;
        synchronized (recv) {
            mutex = (Mutex) recv.getConstantNoConstMissing(MUTEX_FOR_THREAD_EXCLUSIVE, false, false);
            if (mutex == null) {
                mutex = Mutex.newInstance(context, context.runtime.getThread().getClass("Mutex"), NULL_ARRAY, Block.NULL_BLOCK);
                recv.setConstant(MUTEX_FOR_THREAD_EXCLUSIVE, mutex, true);
            }
            return mutex;
        }
    }

    
This is intended to be used to raise exceptions in Ruby threads from non-
Ruby threads like Timeout's thread.
Params:
args – Same args as for Thread#raise/**
     * This is intended to be used to raise exceptions in Ruby threads from non-
     * Ruby threads like Timeout's thread.
     *
     * @param args Same args as for Thread#raise
     */
    @Deprecated
    public void internalRaise(IRubyObject[] args) {
        ThreadContext context = getRuntime().getCurrentContext();
        genericRaise(context, context.getThread(), args);
    }

    @Deprecated
    public void receiveMail(ThreadService.Event event) {
    }

    @Deprecated
    public void checkMail(ThreadContext context) {
    }

    @Deprecated
    private volatile BlockingTask currentBlockingTask;

    @Deprecated
    public boolean selectForAccept(RubyIO io) {
        return select(io, SelectionKey.OP_ACCEPT);
    }

    @Deprecated
    public IRubyObject backtrace20(ThreadContext context, IRubyObject[] args) {
        return backtrace(context);
    }

    @Deprecated
    public IRubyObject backtrace(ThreadContext context, IRubyObject[] args) {
        switch (args.length) {
            case 0:
                return backtrace(context);
            case 1:
                return backtrace(context, args[0]);
            case 2:
                return backtrace(context, args[0], args[1]);
            default:
                Arity.checkArgumentCount(context.runtime, args, 0, 2);
                return null; // not reached
        }
    }

    @Deprecated
    public IRubyObject backtrace_locations(ThreadContext context, IRubyObject[] args) {
        switch (args.length) {
            case 0:
                return backtrace_locations(context);
            case 1:
                return backtrace_locations(context, args[0]);
            case 2:
                return backtrace_locations(context, args[0], args[1]);
            default:
                Arity.checkArgumentCount(context.runtime, args, 0, 2);
                return null; // not reached
        }
    }

    @Deprecated
    public static IRubyObject pass(IRubyObject recv) {
        Ruby runtime = recv.getRuntime();

        return pass(runtime.getCurrentContext(), recv);
    }
}