org.jikesrvm.scheduler

Class ThinLock

java.lang.Object

org.jikesrvm.scheduler.ThinLock

public final class ThinLock
extends Object

Implementation of thin locks.

Field Summary

Fields

Modifier and Type	Field and Description
private static boolean	ENABLE_BIASED_LOCKING
(package private) static int	fastLocks
private static int	retryLimit Number of times a thread yields before inflating the lock on a object to a heavy-weight lock.
(package private) static int	slowLocks
(package private) static boolean	STATS
(package private) static boolean	trace

Constructor Summary

Constructors

Constructor and Description
ThinLock()

Method Summary

Modifier and Type	Method and Description
protected static Lock	attemptToInflate(Object o, Offset lockOffset, Lock l) Promotes a light-weight lock to a heavy-weight lock.
static boolean	attemptToMarkDeflated(Object o, Offset lockOffset, Word oldLockWord)
static boolean	attemptToMarkInflated(Object o, Offset lockOffset, Word oldLockWord, int lockId, int cnt)
private static Word	biasBitsToThinBits(Word bits)
static boolean	casFromBiased(Object o, Offset lockOffset, Word oldLockWord, Word changed, int cnt)
static Lock	getHeavyLock(Object o, Offset lockOffset, boolean create) Obtains the heavy-weight lock, if there is one, associated with the indicated object.
static int	getLockIndex(Word lockWord) Return the lock index for a given lock word.
static int	getLockOwner(Word lockWord)
static int	getRecCount(Word lockWord)
static boolean	holdsLock(Object o, Offset lockOffset, RVMThread thread)
private static Lock	inflate(Object o, Offset lockOffset) Promotes a light-weight lock to a heavy-weight lock.
private static boolean	inflateAndLock(Object o, Offset lockOffset) Promotes a light-weight lock to a heavy-weight lock and locks it.
static void	inlineLock(Object o, Offset lockOffset)
static void	inlineUnlock(Object o, Offset lockOffset)
static boolean	isFat(Word lockWord)
static void	lock(Object o, Offset lockOffset)
static void	markDeflated(Object o, Offset lockOffset, int id)
(package private) static void	notifyAppRunStart(String app, int value)
(package private) static void	notifyExit(int value)
private static void	setDedicatedU16(Object o, Offset lockOffset, Word value) Set only the dedicated locking 16-bit part of the given value.
static void	unlock(Object o, Offset lockOffset)

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Detail

ENABLE_BIASED_LOCKING

private static final boolean ENABLE_BIASED_LOCKING

See Also:

Constant Field Values

retryLimit

private static final int retryLimit

Number of times a thread yields before inflating the lock on a object to a heavy-weight lock. The current value was for the portBOB benchmark on a 12-way SMP (AIX) in the Fall of '99. FP confirmed that it's still optimal for JBB and DaCapo on 4-, 8-, and 16-way SMPs (Linux/ia32) in Spring '09.

See Also:

Constant Field Values

STATS

static final boolean STATS

See Also:

Constant Field Values

trace

static final boolean trace

See Also:

Constant Field Values

fastLocks

static int fastLocks

slowLocks

static int slowLocks

Constructor Detail

ThinLock

public ThinLock()

Method Detail

inlineLock

public static void inlineLock(Object o,
                              Offset lockOffset)

inlineUnlock

public static void inlineUnlock(Object o,
                                Offset lockOffset)

lock

public static void lock(Object o,
                        Offset lockOffset)

unlock

public static void unlock(Object o,
                          Offset lockOffset)

holdsLock

public static boolean holdsLock(Object o,
                                Offset lockOffset,
                                RVMThread thread)

isFat

public static boolean isFat(Word lockWord)

getLockIndex

public static int getLockIndex(Word lockWord)

Return the lock index for a given lock word. Assert valid index ranges, that the fat lock bit is set, and that the lock entry exists.

Parameters:

lockWord - The lock word whose lock index is being established

Returns:

the lock index corresponding to the lock workd.

getLockOwner

public static int getLockOwner(Word lockWord)

getRecCount

public static int getRecCount(Word lockWord)

setDedicatedU16

private static void setDedicatedU16(Object o,
                                    Offset lockOffset,
                                    Word value)

Set only the dedicated locking 16-bit part of the given value. This is the only part that is allowed to be written without a CAS. This takes care of the shifting and storing of the value.

Parameters:

o - The object whose header is to be changed

lockOffset - The lock offset

value - The value which contains the 16-bit portion to be written.

casFromBiased

public static boolean casFromBiased(Object o,
                                    Offset lockOffset,
                                    Word oldLockWord,
                                    Word changed,
                                    int cnt)

attemptToMarkInflated

public static boolean attemptToMarkInflated(Object o,
                                            Offset lockOffset,
                                            Word oldLockWord,
                                            int lockId,
                                            int cnt)

attemptToInflate

protected static Lock attemptToInflate(Object o,
                                       Offset lockOffset,
                                       Lock l)

Promotes a light-weight lock to a heavy-weight lock. If this returns the lock that you gave it, its mutex will be locked; otherwise, its mutex will be unlocked. Hence, calls to this method should always be followed by a condition lock() or unlock() call.

Parameters:

o - the object to get a heavy-weight lock

lockOffset - the offset of the thin lock word in the object.

l - the lock to attempt to inflate

Returns:

the inflated lock; either the one you gave, or another one, if the lock was inflated by some other thread.

biasBitsToThinBits

private static Word biasBitsToThinBits(Word bits)

attemptToMarkDeflated

public static boolean attemptToMarkDeflated(Object o,
                                            Offset lockOffset,
                                            Word oldLockWord)

markDeflated

public static void markDeflated(Object o,
                                Offset lockOffset,
                                int id)

inflate

private static Lock inflate(Object o,
                            Offset lockOffset)

Promotes a light-weight lock to a heavy-weight lock. Note: the object is question will normally be locked by another thread, or it may be unlocked. If there is already a heavy-weight lock on this object, that lock is returned.

Parameters:

o - the object to get a heavy-weight lock

lockOffset - the offset of the thin lock word in the object.

Returns:

the heavy-weight lock on this object

inflateAndLock

private static boolean inflateAndLock(Object o,
                                      Offset lockOffset)

Promotes a light-weight lock to a heavy-weight lock and locks it. Note: the object in question will normally be locked by another thread, or it may be unlocked. If there is already a heavy-weight lock on this object, that lock is returned.

Parameters:

o - the object to get a heavy-weight lock

lockOffset - the offset of the thin lock word in the object.

Returns:

whether the object was successfully locked

getHeavyLock

public static Lock getHeavyLock(Object o,
                                Offset lockOffset,
                                boolean create)

Obtains the heavy-weight lock, if there is one, associated with the indicated object. Returns null, if there is no heavy-weight lock associated with the object.

Parameters:

o - the object from which a lock is desired

lockOffset - the offset of the thin lock word in the object.

create - if true, create heavy lock if none found

Returns:

the heavy-weight lock on the object (if any)

notifyAppRunStart

static void notifyAppRunStart(String app,
                              int value)

notifyExit

static void notifyExit(int value)