com.sun.squawk
Class VMThread

java.lang.Object
  com.sun.squawk.VMThread

All Implemented Interfaces:

GlobalStaticFields

public final class VMThread
extends Object
implements GlobalStaticFields

The Squawk implementation of threads.

See Also:

Monitor

Field Summary

static int	MAX_PRIORITY The maximum priority that a user thread can have.
static int	MAX_SYS_PRIORITY The maximum priority that a system thread can have.
static int	MIN_PRIORITY The minimum priority that a thread can have.
static int	NORM_PRIORITY The default priority that is assigned to a thread.

Constructor Summary

VMThread(Thread apiThread, String name)
Allocates a new VMThread object to support a given API Thread instance.

Method Summary

static int	activeCount() Returns the current number of active threads in the VM.
static VMThread	asVMThread(Thread thread)
void	clearBreakpoint() Clears the object used to report a breakpoint hit.
void	clearStep() Removes the object (if any) that is keeping this thread in single stepping mode.
static VMThread	currentThread() Returns a reference to the currently executing thread object.
Thread	getAPIThread()
static int	getContendedMontorEnterCount() Return the number of times that a thread was blocked trying to synchronize on an object.
int	getDebuggerSuspendCount() Gets the value of the debugger suspension counter for this thread.
int	getErrno() Return the system errno value from the last time a native function was called.
ExecutionPoint	getEventExecutionPoint() Gets the method and frame context of this thread at which a debugger event occurred.
int	getInternalStatus() Gets the combined values for state and queue.
Isolate	getIsolate() Gets the isolate of the thread.
static int	getMaxStackSize() Return size of the largest stack ever allocated, in words.
static int	getMonitorsAllocatedCount() Return the number of monitors allocated.
String	getName() Gets the name of this thread.
int	getPriority() Returns this thread's priority.
static Thread[]	getRunnableThreads()
static int	getStacksAllocatedCount() Return the number of stacks allocated.
Debugger.SingleStep	getStep()
static SystemEvents	getSystemEvents() Handler for OS events...
int	getThreadNumber() Gets the number of this thread which is only guaranteed to be unique within this thread's isolate.
static int	getThreadsAllocatedCount() Return the number of Thread objects allocated during the lifetime of this JVM.
static int	getThreadSwitchCount() Return count of thread context switching.
static long	getTotalWaitTime()
void	interrupt() Interrupts this thread.
boolean	isAlive() Tests if this thread is alive.
boolean	isDaemon() Gets the daemon state of the thread.
boolean	isServiceThread() Determines if this thread is the service thread.
void	join() Waits for this thread to die.
static void	monitorNotify(Object object, boolean notifyAll) Notify an object.
static void	monitorWait(Object object, long delta) Wait for an object to be notified.
void	printStackTrace(PrintStream stream) Print a stack trace for this thread.
void	printState(PrintStream out) Print thread state one one line.
int	resumeForDebugger(boolean forDetach) Decreases the suspension count of this thread.
void	setDaemon(boolean value) Sets the daemon state of the thread.
void	setName(String name) Sets the name of this thread.
void	setPriority(int newPriority) Changes the priority of this thread.
void	setStep(Debugger.SingleStep step) Sets the object that will put this thread into single stepping mode the next time it is scheduled to run.
void	setSystemPriority(int newPriority) Changes the priority of this thread.
static void	signalOSEvent(int event) Restart a thread blocked on an event.
static void	sleep(long millis) Causes the currently executing thread to sleep (temporarily cease execution) for the specified number of milliseconds.
void	start() Causes this thread to begin execution; the Java Virtual Machine calls the run method of this thread.
int	suspendForDebugger() Increases the suspension count of this thread.
String	toString() Returns a string representation of this thread, including a unique number that identifies the thread and the thread's priority.
static void	waitForOSEvent(int event) Block a thread waiting for an event.
static void	yield() Causes the currently executing thread object to temporarily pause and allow other threads to execute.

Methods inherited from class java.lang.Object

equals, getClass, hashCode, notify, notifyAll, wait, wait, wait

Field Detail

MIN_PRIORITY

public static final int MIN_PRIORITY

The minimum priority that a thread can have.

See Also:

Constant Field Values

NORM_PRIORITY

public static final int NORM_PRIORITY

The default priority that is assigned to a thread.

See Also:

Constant Field Values

MAX_PRIORITY

public static final int MAX_PRIORITY

The maximum priority that a user thread can have.

See Also:

Constant Field Values

MAX_SYS_PRIORITY

public static final int MAX_SYS_PRIORITY

The maximum priority that a system thread can have.

See Also:

Constant Field Values

Constructor Detail

VMThread

public VMThread(Thread apiThread,
                String name)

Allocates a new VMThread object to support a given API Thread instance.

This constructor should only be called from a java.lang.Thread constructor.

Parameters:

apiThread - the API thread instance supported by this VM thread

name - the thread name, or null. If null, thread name generated from threadNumber.

Method Detail

getThreadsAllocatedCount

public static int getThreadsAllocatedCount()

Return the number of Thread objects allocated during the lifetime of this JVM.

Returns:

threads allocated

getContendedMontorEnterCount

public static int getContendedMontorEnterCount()

Return the number of times that a thread was blocked trying to synchronize on an object. Note that this counts the initial contention. A thread may be released to aquire the lock, but another thread (potentially higher priority) runs first, and actually acquires the lock. The first thread will then have to wait again.

Returns:

monitor contention count

getMonitorsAllocatedCount

public static int getMonitorsAllocatedCount()

Return the number of monitors allocated. Often, uncontended locking is handled by the interpreter in the pendingMonitors cache. But if the cache is full, or there is contention, or Object.wait() is used, or a thread is switched out while holding a virtual monitor, then a real monitor has to be allocated for an object. It is possible for the monitor for an object to come and go, so there is the possibility of "monitor object thrashing".

Returns:

number of monitors allocated

getThreadSwitchCount

public static int getThreadSwitchCount()

Return count of thread context switching. This does not include system-level switches that occur for GC, exception throwing, etc.

Returns:

user-level thread switches

currentThread

public static VMThread currentThread()

Returns a reference to the currently executing thread object.

Returns:

the currently executing thread

setDaemon

public void setDaemon(boolean value)

Sets the daemon state of the thread. If this thread is alive, an IllegalThreadStateException is thrown.

Parameters:

value - if true, set thread as a daemon

isDaemon

public boolean isDaemon()

Gets the daemon state of the thread.

Returns:

true if thread is a daemon thread

sleep

public static void sleep(long millis)
                  throws InterruptedException

Causes the currently executing thread to sleep (temporarily cease execution) for the specified number of milliseconds. The thread does not lose ownership of any monitors.

Parameters:

millis - the length of time to sleep in milliseconds.

Throws:

InterruptedException - if another thread has interrupted the current thread. The interrupted status of the current thread is cleared when this exception is thrown.

See Also:

Object.notify()

yield

public static void yield()

Causes the currently executing thread object to temporarily pause and allow other threads to execute.

start

public void start()

Causes this thread to begin execution; the Java Virtual Machine calls the run method of this thread.

The result is that two threads are running concurrently: the current thread (which returns from the call to the start method) and the other thread (which executes its run method).

Throws:

IllegalThreadStateException - if the thread was already started.

See Also:

Thread.run()

isAlive

public final boolean isAlive()

Tests if this thread is alive. A thread is alive if it has been started and has not yet died.

Returns:

true if this thread is alive; false otherwise.

setPriority

public final void setPriority(int newPriority)

Changes the priority of this thread.

Parameters:

newPriority - priority to set this thread to

Throws:

IllegalArgumentException - If the priority is not in the range MIN_PRIORITY to MAX_PRIORITY.

See Also:

getPriority(), Thread.getPriority(), Thread.MAX_PRIORITY, Thread.MIN_PRIORITY

setSystemPriority

public final void setSystemPriority(int newPriority)

Changes the priority of this thread. Allows setting priority to "system" levels.

Parameters:

newPriority - priority to set this thread to

Throws:

IllegalArgumentException - If the priority is not in the range MIN_PRIORITY to MAX_SYS_PRIORITY.

See Also:

getPriority(), Thread.getPriority(), Thread.MAX_PRIORITY, Thread.MIN_PRIORITY

getPriority

public final int getPriority()

Returns this thread's priority.

Returns:

this thread's name.

See Also:

setPriority(int), Thread.setPriority(int)

activeCount

public static int activeCount()

Returns the current number of active threads in the VM.

Returns:

the current number of active threads

join

public final void join()
                throws InterruptedException

Waits for this thread to die.

Throws:

InterruptedException - if another thread has interrupted the current thread. The interrupted status of the current thread is cleared when this exception is thrown.

getName

public final String getName()

Gets the name of this thread. If setName(java.lang.String) has never been called for this thread, the return value will be of the from "Thread-" where 'n' is a unique numeric identifier for this thread.

Returns:

thread name in standard format

setName

public final void setName(String name)

Sets the name of this thread.

Parameters:

name - the new name for this thread

toString

public String toString()

Returns a string representation of this thread, including a unique number that identifies the thread and the thread's priority.

Overrides:

toString in class Object

Returns:

a string representation of this thread.

getSystemEvents

public static SystemEvents getSystemEvents()

Handler for OS events...

getDebuggerSuspendCount

public final int getDebuggerSuspendCount()

Gets the value of the debugger suspension counter for this thread.

Returns:

the suspension count for this thread

suspendForDebugger

public final int suspendForDebugger()

Increases the suspension count of this thread.

Returns:

the new suspension count for this thread

resumeForDebugger

public final int resumeForDebugger(boolean forDetach)

Decreases the suspension count of this thread.

Parameters:

forDetach - if true, the count is set to 0

Returns:

the new suspension count for this thread

getEventExecutionPoint

public ExecutionPoint getEventExecutionPoint()

Gets the method and frame context of this thread at which a debugger event occurred.

Returns:

null if this thread is not currently reporting an event to the debugger subsystem

getInternalStatus

public final int getInternalStatus()

Gets the combined values for state and queue.

Returns:

the queue in the least significant byte, and the state in the next least significant byte.

getStep

public final Debugger.SingleStep getStep()

Returns:

Returns the step info object.

setStep

public final void setStep(Debugger.SingleStep step)

Sets the object that will put this thread into single stepping mode the next time it is scheduled to run.

Parameters:

step - the details of the requested step

clearStep

public final void clearStep()

Removes the object (if any) that is keeping this thread in single stepping mode.

clearBreakpoint

public void clearBreakpoint()

Clears the object used to report a breakpoint hit.

getIsolate

public Isolate getIsolate()

Gets the isolate of the thread.

Returns:

the isolate

getAPIThread

public Thread getAPIThread()

asVMThread

public static VMThread asVMThread(Thread thread)

isServiceThread

public boolean isServiceThread()

Determines if this thread is the service thread.

getThreadNumber

public final int getThreadNumber()

Gets the number of this thread which is only guaranteed to be unique within this thread's isolate.

Returns:

an integer identifier for this thread

getStacksAllocatedCount

public static int getStacksAllocatedCount()

Return the number of stacks allocated. Stacks are allocated for each thread, and as more frames are needed, new stacks are created to replace the original stacks (typically at 2x the size of the original stack). The default stack size is about 160 words.

Returns:

total number of stacks ever allocated

getMaxStackSize

public static int getMaxStackSize()

Return size of the largest stack ever allocated, in words.

Returns:

largest stack size ever allocated

getTotalWaitTime

public static long getTotalWaitTime()

printState

public void printState(PrintStream out)

Print thread state one one line. Will print on the stream out unless an error occurs while printing on that stream, such as a null stream, or IO error on the stream. If a printing error occurs, this falls back on printing via VM.print(), etc.

Parameters:

out - the stream to print on.

printStackTrace

public void printStackTrace(PrintStream stream)

Print a stack trace for this thread.

Will print on the stream out unless an error occurs while printing on that stream, such as a null stream, or IO error on the stream. If a printing error occurs, this falls back on printing via VM.print(), etc.

Parameters:

stream -

waitForOSEvent

public static void waitForOSEvent(int event)

Block a thread waiting for an event.

Parameters:

event - the event number to wait for

signalOSEvent

public static void signalOSEvent(int event)

Restart a thread blocked on an event.

Parameters:

event - the event number to unblock

getErrno

public int getErrno()

Return the system errno value from the last time a native function was called.

Returns:

zero if no error

monitorWait

public static void monitorWait(Object object,
                               long delta)
                        throws InterruptedException

Wait for an object to be notified.

Parameters:

object - the object to wait on

delta - the timeout period

Throws:

InterruptedException - if another thread has interrupted the current thread. The interrupted status of the current thread is cleared when this exception is thrown.

monitorNotify

public static void monitorNotify(Object object,
                                 boolean notifyAll)

Notify an object.

Parameters:

object - the object be notified

notifyAll - flag to notify all waiting threads

interrupt

public void interrupt()

Interrupts this thread.

This method does nothing if the current thread is interrupting itself.

If this thread is blocked in an invocation of the Object.wait(), Object.wait(long), or Object.wait(long, int) methods of the class, or of the Thread.join(), Thread#join(long), Thread#join(long, int), Thread.sleep(long), or Thread#sleep(long, int) methods of this class, then its interrupt status will be cleared and it will receive an InterruptedException.

If none of the previous conditions hold then this thread's interrupt status will be set.

getRunnableThreads

public static Thread[] getRunnableThreads()