001 /*
002 * This file is part of the Jikes RVM project (http://jikesrvm.org).
003 *
004 * This file is licensed to You under the Eclipse Public License (EPL);
005 * You may not use this file except in compliance with the License. You
006 * may obtain a copy of the License at
007 *
008 * http://www.opensource.org/licenses/eclipse-1.0.php
009 *
010 * See the COPYRIGHT.txt file distributed with this work for information
011 * regarding copyright ownership.
012 */
013 package org.jikesrvm.objectmodel;
014
015 import org.jikesrvm.SizeConstants;
016 import org.jikesrvm.scheduler.RVMThread;
017 import org.vmmagic.unboxed.Word;
018
019 /**
020 * Constants used to implement thin locks.
021 * <p>
022 * A portion of a word, either in the object header
023 * or in some other location, is used to provide light weight
024 * synchronization operations. This class defines
025 * how the bits available for thin locks are allocated.
026 * Either a lock is in fat state, in which case it looks like
027 * 1Z..Z where Z..Z is the id of a heavy lock, or it is in
028 * thin state in which case it looks like 0I..IC..C where
029 * I is the thread id of the thread that owns the lock and
030 * C is the recursion count of the lock.
031 * <pre>
032 * aaaaTTTTTTTTTTbbbbb
033 * JavaHeader.NUM_THIN_LOCK_BITS = # of T's
034 * JavaHeader.THIN_LOCK_SHIFT = # of b's
035 * </pre>
036 */
037 public interface ThinLockConstants extends SizeConstants {
038
039 // biased locking / thin locking status bits:
040 // 00 -> thin biasable, and biased if TID is non-zero
041 // 01 -> thin unbiasable
042 // 10 -> fat unbiasable
043
044 int TL_NUM_BITS_STAT = 2;
045 int TL_NUM_BITS_TID = RVMThread.LOG_MAX_THREADS;
046 int TL_NUM_BITS_RC = JavaHeader.NUM_THIN_LOCK_BITS - TL_NUM_BITS_TID - TL_NUM_BITS_STAT;
047
048 int TL_THREAD_ID_SHIFT = JavaHeader.THIN_LOCK_SHIFT;
049 int TL_LOCK_COUNT_SHIFT = TL_THREAD_ID_SHIFT + TL_NUM_BITS_TID;
050 int TL_STAT_SHIFT = TL_LOCK_COUNT_SHIFT + TL_NUM_BITS_RC;
051 int TL_LOCK_ID_SHIFT = JavaHeader.THIN_LOCK_SHIFT;
052 int TL_DEDICATED_U16_OFFSET = JavaHeader.THIN_LOCK_DEDICATED_U16_OFFSET;
053 int TL_DEDICATED_U16_SHIFT = JavaHeader.THIN_LOCK_DEDICATED_U16_SHIFT;
054
055 Word TL_LOCK_COUNT_UNIT = Word.fromIntSignExtend(1 << TL_LOCK_COUNT_SHIFT);
056
057 Word TL_LOCK_COUNT_MASK = Word.fromIntSignExtend(-1).rshl(BITS_IN_ADDRESS - TL_NUM_BITS_RC).lsh(TL_LOCK_COUNT_SHIFT);
058 Word TL_THREAD_ID_MASK = Word.fromIntSignExtend(-1).rshl(BITS_IN_ADDRESS - TL_NUM_BITS_TID).lsh(TL_THREAD_ID_SHIFT);
059 Word TL_LOCK_ID_MASK =
060 Word.fromIntSignExtend(-1).rshl(BITS_IN_ADDRESS - (TL_NUM_BITS_RC + TL_NUM_BITS_TID)).lsh(TL_LOCK_ID_SHIFT);
061 Word TL_STAT_MASK = Word.fromIntSignExtend(-1).rshl(BITS_IN_ADDRESS - TL_NUM_BITS_TID).lsh(TL_STAT_SHIFT);
062 Word TL_UNLOCK_MASK = Word.fromIntSignExtend(-1).rshl(BITS_IN_ADDRESS - JavaHeader
063 .NUM_THIN_LOCK_BITS).lsh(JavaHeader.THIN_LOCK_SHIFT).not();
064
065 Word TL_STAT_BIASABLE = Word.fromIntSignExtend(0).lsh(TL_STAT_SHIFT);
066 Word TL_STAT_THIN = Word.fromIntSignExtend(1).lsh(TL_STAT_SHIFT);
067 Word TL_STAT_FAT = Word.fromIntSignExtend(2).lsh(TL_STAT_SHIFT);
068 }
069