8005697: Add StampedLock

Reviewed-by: chegar, alanb, dice, martin

jdk/make/java/java/FILES_java.gmk

@@ -389,6 +389,7 @@ JAVA_JAVA_java = \
     java/util/concurrent/locks/ReadWriteLock.java \
     java/util/concurrent/locks/ReentrantLock.java \
     java/util/concurrent/locks/ReentrantReadWriteLock.java \
+    java/util/concurrent/locks/StampedLock.java \
     java/util/regex/Pattern.java \
     java/util/regex/Matcher.java \
     java/util/regex/MatchResult.java \

jdk/src/share/classes/java/util/concurrent/locks/LockSupport.java

@@ -101,14 +101,14 @@ import sun.misc.Unsafe;
  *     // Block while not first in queue or cannot acquire lock
  *     while (waiters.peek() != current ||
  *            !locked.compareAndSet(false, true)) {
- *        LockSupport.park(this);
- *        if (Thread.interrupted()) // ignore interrupts while waiting
- *          wasInterrupted = true;
+ *       LockSupport.park(this);
+ *       if (Thread.interrupted()) // ignore interrupts while waiting
+ *         wasInterrupted = true;
  *     }
  *
  *     waiters.remove();
  *     if (wasInterrupted)          // reassert interrupt status on exit
- *        current.interrupt();
+ *       current.interrupt();
  *   }
  *
  *   public void unlock() {
@@ -120,20 +120,9 @@ import sun.misc.Unsafe;
 public class LockSupport {
     private LockSupport() {} // Cannot be instantiated.
 
-    // Hotspot implementation via intrinsics API
-    private static final Unsafe unsafe = Unsafe.getUnsafe();
-    private static final long parkBlockerOffset;
-
-    static {
-        try {
-            parkBlockerOffset = unsafe.objectFieldOffset
-                (java.lang.Thread.class.getDeclaredField("parkBlocker"));
-        } catch (Exception ex) { throw new Error(ex); }
-    }
-
     private static void setBlocker(Thread t, Object arg) {
         // Even though volatile, hotspot doesn't need a write barrier here.
-        unsafe.putObject(t, parkBlockerOffset, arg);
+        UNSAFE.putObject(t, parkBlockerOffset, arg);
     }
 
     /**
@@ -149,7 +138,7 @@ public class LockSupport {
      */
     public static void unpark(Thread thread) {
         if (thread != null)
-            unsafe.unpark(thread);
+            UNSAFE.unpark(thread);
     }
 
     /**
@@ -183,7 +172,7 @@ public class LockSupport {
     public static void park(Object blocker) {
         Thread t = Thread.currentThread();
         setBlocker(t, blocker);
-        unsafe.park(false, 0L);
+        UNSAFE.park(false, 0L);
         setBlocker(t, null);
     }
 
@@ -223,7 +212,7 @@ public class LockSupport {
         if (nanos > 0) {
             Thread t = Thread.currentThread();
             setBlocker(t, blocker);
-            unsafe.park(false, nanos);
+            UNSAFE.park(false, nanos);
             setBlocker(t, null);
         }
     }
@@ -264,7 +253,7 @@ public class LockSupport {
     public static void parkUntil(Object blocker, long deadline) {
         Thread t = Thread.currentThread();
         setBlocker(t, blocker);
-        unsafe.park(true, deadline);
+        UNSAFE.park(true, deadline);
         setBlocker(t, null);
     }
 
@@ -283,7 +272,7 @@ public class LockSupport {
     public static Object getBlocker(Thread t) {
         if (t == null)
             throw new NullPointerException();
-        return unsafe.getObjectVolatile(t, parkBlockerOffset);
+        return UNSAFE.getObjectVolatile(t, parkBlockerOffset);
     }
 
     /**
@@ -312,7 +301,7 @@ public class LockSupport {
      * for example, the interrupt status of the thread upon return.
      */
     public static void park() {
-        unsafe.park(false, 0L);
+        UNSAFE.park(false, 0L);
     }
 
     /**
@@ -346,7 +335,7 @@ public class LockSupport {
      */
     public static void parkNanos(long nanos) {
         if (nanos > 0)
-            unsafe.park(false, nanos);
+            UNSAFE.park(false, nanos);
     }
 
     /**
@@ -380,6 +369,46 @@ public class LockSupport {
      *        to wait until
      */
     public static void parkUntil(long deadline) {
-        unsafe.park(true, deadline);
+        UNSAFE.park(true, deadline);
     }
+
+    /**
+     * Returns the pseudo-randomly initialized or updated secondary seed.
+     * Copied from ThreadLocalRandom due to package access restrictions.
+     */
+    static final int nextSecondarySeed() {
+        int r;
+        Thread t = Thread.currentThread();
+        if ((r = UNSAFE.getInt(t, SECONDARY)) != 0) {
+            r ^= r << 13;   // xorshift
+            r ^= r >>> 17;
+            r ^= r << 5;
+        }
+        else if ((r = java.util.concurrent.ThreadLocalRandom.current().nextInt()) == 0)
+            r = 1; // avoid zero
+        UNSAFE.putInt(t, SECONDARY, r);
+        return r;
+    }
+
+    // Hotspot implementation via intrinsics API
+    private static final sun.misc.Unsafe UNSAFE;
+    private static final long parkBlockerOffset;
+    private static final long SEED;
+    private static final long PROBE;
+    private static final long SECONDARY;
+    static {
+        try {
+            UNSAFE = sun.misc.Unsafe.getUnsafe();
+            Class<?> tk = Thread.class;
+            parkBlockerOffset = UNSAFE.objectFieldOffset
+                (tk.getDeclaredField("parkBlocker"));
+            SEED = UNSAFE.objectFieldOffset
+                (tk.getDeclaredField("threadLocalRandomSeed"));
+            PROBE = UNSAFE.objectFieldOffset
+                (tk.getDeclaredField("threadLocalRandomProbe"));
+            SECONDARY = UNSAFE.objectFieldOffset
+                (tk.getDeclaredField("threadLocalRandomSecondarySeed"));
+        } catch (Exception ex) { throw new Error(ex); }
+    }
+
 }

jdk/test/java/util/concurrent/locks/StampedLock/Basic.java

@@ -0,0 +1,609 @@
+/*
+ * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
+ *
+ * This code is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 only, as
+ * published by the Free Software Foundation.
+ *
+ * This code is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+ * version 2 for more details (a copy is included in the LICENSE file that
+ * accompanied this code).
+ *
+ * You should have received a copy of the GNU General Public License version
+ * 2 along with this work; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
+ * or visit www.oracle.com if you need additional information or have any
+ * questions.
+ */
+
+/*
+ * This file is available under and governed by the GNU General Public
+ * License version 2 only, as published by the Free Software Foundation.
+ * However, the following notice accompanied the original version of this
+ * file:
+ *
+ * Written by Doug Lea with assistance from members of JCP JSR-166
+ * Expert Group and released to the public domain, as explained at
+ * http://creativecommons.org/publicdomain/zero/1.0/
+ */
+
+/*
+ * @test
+ * @bug 8005697
+ * @summary Basic tests for StampedLock
+ * @author Chris Hegarty
+ */
+
+import java.util.Iterator;
+import java.util.concurrent.Phaser;
+import java.util.concurrent.TimeUnit;
+import static java.util.concurrent.TimeUnit.*;
+import java.util.concurrent.atomic.AtomicInteger;
+import java.util.concurrent.locks.Lock;
+import java.util.concurrent.locks.ReadWriteLock;
+import java.util.concurrent.locks.StampedLock;
+
+public class Basic {
+
+    static void checkResult(Locker l, Class<? extends Throwable> c) {
+        Throwable t = l.thrown();
+        if (! ((t == null && c == null) || (c != null && c.isInstance(t)))) {
+            fail("Mismatch in thread " +
+                 l.getName() + ": " +
+                 t + ", " +
+                 (c == null ? "<null>" : c.getName()));
+        }
+
+        if (c == null)
+            check(l.stamp() != 0L);  // must have acquired the lock
+        else
+            check(l.stamp() == 0L);  // must NOT have acquired the lock
+    }
+
+    //----------------------------------------------------------------
+    // Mechanism to get all test threads into "running" mode.
+    //----------------------------------------------------------------
+    static void toTheStartingGate(Phaser gate) {
+        try {
+            gate.arriveAndAwaitAdvance();
+        } catch (Throwable t) {
+            unexpected(t);
+        }
+    }
+
+    static abstract class Locker extends Thread {
+        static AtomicInteger count = new AtomicInteger(1);
+        private volatile Throwable thrown;
+        private volatile long stamp;;
+        protected void thrown(Throwable thrown) { this.thrown = thrown; }
+        public Throwable thrown() { return thrown; }
+        protected void stamp(long stamp) { this.stamp = stamp; }
+        public long stamp() { return stamp; }
+
+        Locker() {
+            this("Locker");
+        }
+
+        Locker(String name) {
+            this.setName(name + ":" + count.getAndIncrement());
+            this.setDaemon(true);
+        }
+    }
+
+    static abstract class Reader extends Locker {
+        Reader() { super("Reader"); }
+        Reader(String name) { super(name); }
+    }
+
+    static Reader reader(final StampedLock sl, final Phaser gate) {
+        return new Reader() { public void run() {
+            if (gate != null ) toTheStartingGate(gate);
+            stamp(sl.readLock());
+            try {
+                check(sl.validate(stamp()));
+                check(sl.isReadLocked());
+                check(!sl.isWriteLocked());
+            } finally { sl.unlockRead(stamp()); } }};
+    }
+
+    static Reader readerView(final StampedLock sl, final Phaser gate) {
+        return new Reader("ReaderView") { public void run() {
+            if (gate != null ) toTheStartingGate(gate);
+            final Lock rl = sl.asReadLock();
+            rl.lock();
+            try {
+                stamp(1L);   // got the lock
+                check(sl.isReadLocked());
+                check(!sl.isWriteLocked());
+            } finally { rl.unlock(); } }};
+    }
+
+    static Reader reader(StampedLock sl, Phaser gate, boolean view) {
+        return view ? readerView(sl, gate) : reader(sl, gate);
+    }
+
+    static Reader interruptibleReader(final StampedLock sl,
+                                      final long timeout,
+                                      final TimeUnit unit,
+                                      final Phaser gate) {
+        return new Reader("InterruptibleReader") { public void run() {
+            if (gate != null ) toTheStartingGate(gate);
+            try {
+                if (timeout < 0)
+                    stamp(sl.readLockInterruptibly());
+                else
+                    stamp(sl.tryReadLock(timeout, unit));
+                check(sl.validate(stamp()));
+                check(sl.isReadLocked());
+                check(!sl.isWriteLocked());
+            } catch (Throwable x) { thrown(x);
+            } finally { if (stamp() != 0L) sl.unlockRead(stamp()); } }};
+    }
+
+    static Reader interruptibleReaderView(final StampedLock sl,
+                                          final long timeout,
+                                          final TimeUnit unit,
+                                          final Phaser gate) {
+        return new Reader("InterruptibleReaderView") { public void run() {
+            if (gate != null ) toTheStartingGate(gate);
+            final Lock rl = sl.asReadLock();
+
+            try {
+                if (timeout < 0)
+                    rl.lockInterruptibly();
+                else
+                    rl.tryLock(timeout, unit);
+                stamp(1L);  // got the lock
+                check(sl.isReadLocked());
+                check(!sl.isWriteLocked());
+            } catch (Throwable x) { thrown(x);
+            } finally { if (stamp() != 0L) rl.unlock(); } }};
+    }
+
+    static Reader interruptibleReader(final StampedLock sl,
+                                      final long timeout,
+                                      final TimeUnit unit,
+                                      final Phaser gate,
+                                      final boolean view) {
+        return view ? interruptibleReaderView(sl, timeout, unit, gate)
+                    : interruptibleReader(sl, timeout, unit, gate);
+    }
+
+    static abstract class Writer extends Locker {
+        Writer() { super("Writer"); }
+        Writer(String name) { super(name); }
+    }
+
+    static Writer writer(final StampedLock sl, final Phaser gate) {
+        return new Writer() { public void run() {
+            if (gate != null ) toTheStartingGate(gate);
+            try {
+                stamp(sl.writeLock());
+                check(sl.validate(stamp()));
+                check(!sl.isReadLocked());
+                check(sl.isWriteLocked());
+            } finally { sl.unlockWrite(stamp()); } }};
+    }
+
+    static Writer writerView(final StampedLock sl, final Phaser gate) {
+        return new Writer("WriterView") { public void run() {
+            if (gate != null ) toTheStartingGate(gate);
+            Lock wl = sl.asWriteLock();
+            wl.lock();
+            try {
+                stamp(1L);  // got the lock
+                check(!sl.isReadLocked());
+                check(sl.isWriteLocked());
+            } finally { wl.unlock(); } }};
+    }
+
+    static Writer writer(StampedLock sl, Phaser gate, boolean view) {
+        return view ? writerView(sl, gate) : writer(sl, gate);
+    }
+
+    static Writer interruptibleWriter(final StampedLock sl,
+                                      final long timeout,
+                                      final TimeUnit unit,
+                                      final Phaser gate) {
+        return new Writer("InterruptibleWriter") { public void run() {
+            if (gate != null ) toTheStartingGate(gate);
+            try {
+                if (timeout < 0)
+                    stamp(sl.writeLockInterruptibly());
+                else
+                    stamp(sl.tryWriteLock(timeout, unit));
+                check(sl.validate(stamp()));
+                check(!sl.isReadLocked());
+                check(sl.isWriteLocked());
+            } catch (Throwable x) { thrown(x);
+            } finally { if (stamp() != 0L) sl.unlockWrite(stamp()); } }};
+    }
+
+    static Writer interruptibleWriterView(final StampedLock sl,
+                                          final long timeout,
+                                          final TimeUnit unit,
+                                          final Phaser gate) {
+        return new Writer("InterruptibleWriterView") { public void run() {
+            if (gate != null ) toTheStartingGate(gate);
+            Lock wl = sl.asWriteLock();
+            try {
+                if (timeout < 0)
+                    wl.lockInterruptibly();
+                else
+                    wl.tryLock(timeout, unit);
+                stamp(1L);  // got the lock
+                check(!sl.isReadLocked());
+                check(sl.isWriteLocked());
+            } catch (Throwable x) { thrown(x);
+            } finally { if (stamp() != 0L) wl.unlock(); } }};
+    }
+
+    static Writer interruptibleWriter(final StampedLock sl,
+                                      final long timeout,
+                                      final TimeUnit unit,
+                                      final Phaser gate,
+                                      final boolean view) {
+        return view ? interruptibleWriterView(sl, timeout, unit, gate)
+                    : interruptibleWriter(sl, timeout, unit, gate);
+    }
+
+    // Returns an infinite lazy list of all possible reader combinations.
+    static Iterator<Reader> readerIterator(final StampedLock sl,
+                                           final Phaser gate) {
+        return new Iterator<Reader>() {
+            int i = 0;
+            boolean view = false;
+            public boolean hasNext() { return true; }
+            public Reader next() {
+                switch ((i++)&7) {
+                    case 1: case 4: case 7:
+                        return reader(sl, gate, view ^= true);
+                    case 2: case 5:
+                        return interruptibleReader(sl, -1, SECONDS, gate, view ^= true);
+                    default:
+                        return interruptibleReader(sl, 30, SECONDS, gate, view ^= true); }}
+            public void remove() {throw new UnsupportedOperationException();}};
+    }
+
+    // Returns an infinite lazy list of all possible writer combinations.
+    static Iterator<Writer> writerIterator(final StampedLock sl,
+                                           final Phaser gate) {
+        return new Iterator<Writer>() {
+            int i = 0;
+            boolean view = false;
+            public boolean hasNext() { return true; }
+            public Writer next() {
+                switch ((i++)&7) {
+                    case 1: case 4: case 7:
+                        return writer(sl, gate, view ^= true);
+                    case 2: case 5:
+                        return interruptibleWriter(sl, -1, SECONDS, gate, view ^= true);
+                    default:
+                        return interruptibleWriter(sl, 30, SECONDS, gate, view ^= true); }}
+            public void remove() {throw new UnsupportedOperationException();}};
+    }
+
+    private static void realMain(String[] args) throws Throwable {
+
+        Thread.currentThread().setName("mainThread");
+
+        //----------------------------------------------------------------
+        // Some basic sanity
+        //----------------------------------------------------------------
+        try {
+            final StampedLock sl = new StampedLock();
+            check(!sl.isReadLocked());
+            check(!sl.isWriteLocked());
+            long stamp = sl.tryOptimisticRead();
+            check(stamp != 0L);
+            check(sl.validate(stamp));
+            check(!sl.validate(0));
+
+            stamp = sl.writeLock();
+            try {
+                check(sl.validate(stamp));
+                check(!sl.isReadLocked());
+                check(sl.isWriteLocked());
+                check(sl.tryReadLock() == 0L);
+                check(sl.tryReadLock(100, MILLISECONDS) == 0L);
+                check(sl.tryOptimisticRead() == 0L);
+                check(sl.tryWriteLock() == 0L);
+                check(sl.tryWriteLock(100, MILLISECONDS) == 0L);
+                check(!sl.tryUnlockRead());
+                check(sl.tryConvertToWriteLock(stamp) == stamp);
+                try {
+                    sl.unlockRead(stamp);
+                    fail("Expected unlockRead to throw when not holding read lock");
+                } catch (IllegalMonitorStateException x) {
+                    pass();
+                }
+                check(sl.validate(stamp));
+            } finally {
+                sl.unlockWrite(stamp);
+            }
+            check(!sl.isWriteLocked());
+
+            stamp = sl.readLock();
+            try {
+                check(sl.validate(stamp));
+                check(sl.isReadLocked());
+                check(!sl.isWriteLocked());
+                check(sl.tryOptimisticRead() != 0L);
+                check(sl.tryWriteLock() == 0L);
+                check(sl.tryWriteLock(100, MILLISECONDS) == 0L);
+                check(!sl.tryUnlockWrite());
+                check(sl.tryConvertToReadLock(stamp) == stamp);
+                try {
+                    sl.unlockWrite(stamp);
+                    fail("Expected unlockWrite to throw when not holding read lock");
+                } catch (IllegalMonitorStateException x) {
+                    pass();
+                }
+                check(sl.validate(stamp));
+            } finally {
+                sl.unlockRead(stamp);
+            }
+            check(!sl.isReadLocked());
+
+            stamp = sl.tryReadLock(100, MILLISECONDS);
+            try {
+                check(stamp != 0L);
+            } finally {
+                sl.unlockRead(stamp);
+            }
+        } catch (Throwable t) { unexpected(t); }
+
+        //----------------------------------------------------------------
+        // Multiple writers single reader
+        //----------------------------------------------------------------
+        try {
+            StampedLock sl = new StampedLock();
+            Phaser gate = new Phaser(102);
+            Iterator<Writer> writers = writerIterator(sl, gate);
+            Iterator<Reader> readers = readerIterator(sl, gate);
+            for (int i = 0; i < 10; i++) {
+                check(!sl.isReadLocked());
+                check(!sl.isWriteLocked());
+                check(!sl.tryUnlockRead());
+                check(!sl.tryUnlockWrite());
+                check(sl.tryOptimisticRead() != 0L);
+                Locker[] wThreads = new Locker[100];;
+                for (int j=0; j<100; j++)
+                    wThreads[j] = writers.next();
+                for (int j=0; j<100; j++)
+                    wThreads[j].start();
+                Reader reader = readers.next(); reader.start();
+                toTheStartingGate(gate);
+                reader.join();
+                for (int j=0; j<100; j++)
+                    wThreads[j].join();
+                for (int j=0; j<100; j++)
+                    checkResult(wThreads[j], null);
+                checkResult(reader, null);
+            }
+        } catch (Throwable t) { unexpected(t); }
+
+        //----------------------------------------------------------------
+        // Multiple readers single writer
+        //----------------------------------------------------------------
+        try {
+            StampedLock sl = new StampedLock();
+            Phaser gate = new Phaser(102);
+            Iterator<Writer> writers = writerIterator(sl, gate);
+            Iterator<Reader> readers = readerIterator(sl, gate);
+            for (int i = 0; i < 10; i++) {
+                check(!sl.isReadLocked());
+                check(!sl.isWriteLocked());
+                check(!sl.tryUnlockRead());
+                check(!sl.tryUnlockWrite());
+                check(sl.tryOptimisticRead() != 0L);
+                Locker[] rThreads = new Locker[100];;
+                for (int j=0; j<100; j++)
+                    rThreads[j] = readers.next();
+                for (int j=0; j<100; j++)
+                    rThreads[j].start();
+                Writer writer = writers.next(); writer.start();
+                toTheStartingGate(gate);
+                writer.join();
+                for (int j=0; j<100; j++)
+                    rThreads[j].join();
+                for (int j=0; j<100; j++)
+                    checkResult(rThreads[j], null);
+                checkResult(writer, null);
+            }
+        } catch (Throwable t) { unexpected(t); }
+
+        //----------------------------------------------------------------
+        // thread interrupted
+        //----------------------------------------------------------------
+        try {
+            boolean view = false;
+            StampedLock sl = new StampedLock();
+            for (long timeout : new long[] { -1L, 30L, -1L, 30L }) {
+                long stamp = sl.writeLock();
+                try {
+                    Reader r = interruptibleReader(sl, timeout, SECONDS, null, view);
+                    r.start();
+                    // allow r to block
+                    Thread.sleep(2000);
+                    r.interrupt();
+                    r.join();
+                    checkResult(r, InterruptedException.class);
+                } finally {
+                    sl.unlockWrite(stamp);
+                }
+                stamp = sl.readLock();
+                try {
+                    Writer w = interruptibleWriter(sl, timeout, SECONDS, null, view);
+                    w.start();
+                    // allow w to block
+                    Thread.sleep(2000);
+                    w.interrupt();
+                    w.join();
+                    checkResult(w, InterruptedException.class);
+                } finally {
+                    sl.unlockRead(stamp);
+                }
+                check(!sl.isReadLocked());
+                check(!sl.isWriteLocked());
+                check(!sl.tryUnlockRead());
+                check(!sl.tryUnlockWrite());
+                check(sl.tryOptimisticRead() != 0L);
+                if (timeout == 30L)
+                    view = true;
+            }
+        } catch (Throwable t) { unexpected(t); }
+
+        //----------------------------------------------------------------
+        // timeout
+        //----------------------------------------------------------------
+        try {
+            StampedLock sl = new StampedLock();
+            for (long timeout : new long[] { 0L, 5L }) {
+                long stamp = sl.writeLock();
+                try {
+                    check(sl.tryReadLock(timeout, SECONDS) == 0L);
+                } finally {
+                    sl.unlockWrite(stamp);
+                }
+                stamp = sl.readLock();
+                try {
+                    check(sl.tryWriteLock(timeout, SECONDS) == 0L);
+                } finally {
+                    sl.unlockRead(stamp);
+                }
+                check(!sl.isReadLocked());
+                check(!sl.isWriteLocked());
+                check(!sl.tryUnlockRead());
+                check(!sl.tryUnlockWrite());
+                check(sl.tryOptimisticRead() != 0L);
+            }
+        } catch (Throwable t) { unexpected(t); }
+
+        //----------------------------------------------------------------
+        // optimistic read
+        //----------------------------------------------------------------
+        try {
+            StampedLock sl = new StampedLock();
+            Iterator<Writer> writers = writerIterator(sl, null);
+            Iterator<Reader> readers = readerIterator(sl, null);
+            for (int i = 0; i < 10; i++) {
+                check(!sl.isReadLocked());
+                check(!sl.isWriteLocked());
+                check(!sl.tryUnlockRead());
+                check(!sl.tryUnlockWrite());
+                long stamp = sl.tryOptimisticRead();
+                check(stamp != 0L);
+                check(sl.tryConvertToOptimisticRead(stamp) == stamp);
+                Reader r = readers.next(); r.start();
+                r.join();
+                checkResult(r, null);
+                check(sl.validate(stamp));
+                check(sl.tryConvertToOptimisticRead(stamp) == stamp);
+                Writer w = writers.next(); w.start();
+                w.join();
+                checkResult(w, null);
+                check(sl.validate(stamp) == false);
+            }
+        } catch (Throwable t) { unexpected(t); }
+
+        //----------------------------------------------------------------
+        // convert
+        //----------------------------------------------------------------
+        try {
+            StampedLock sl = new StampedLock();
+            for (int i = 0; i < 2; i++) {
+                check(!sl.isReadLocked());
+                check(!sl.isWriteLocked());
+                check(!sl.tryUnlockRead());
+                check(!sl.tryUnlockWrite());
+                long stamp = sl.tryOptimisticRead();
+                check(stamp != 0L);
+                check((stamp = sl.tryConvertToReadLock(stamp)) != 0L);
+                check(sl.validate(stamp));
+                check(sl.isReadLocked());
+                check(sl.tryWriteLock() == 0L);
+                check(sl.tryWriteLock(1L, SECONDS) == 0L);
+                check((stamp = sl.tryConvertToWriteLock(stamp)) != 0L);
+                check(sl.validate(stamp));
+                check(!sl.isReadLocked());
+                check(sl.isWriteLocked());
+                check(sl.tryReadLock(1L, SECONDS) == 0L);
+                if (i != 0) {
+                    sl.unlockWrite(stamp);
+                    continue;
+                }
+                // convert down
+                check((stamp = sl.tryConvertToReadLock(stamp)) != 0L);
+                check(sl.validate(stamp));
+                check(sl.isReadLocked());
+                check(!sl.isWriteLocked());
+                check(sl.tryWriteLock() == 0L);
+                check(sl.tryWriteLock(1L, SECONDS) == 0L);
+                check((stamp = sl.tryConvertToOptimisticRead(stamp)) != 0L);
+                check(sl.validate(stamp));
+                check(!sl.isReadLocked());
+                check(!sl.isWriteLocked());
+                check(sl.validate(stamp));
+            }
+        } catch (Throwable t) { unexpected(t); }
+
+        //----------------------------------------------------------------
+        // views
+        //----------------------------------------------------------------
+        try {
+            StampedLock sl = new StampedLock();
+
+            Lock rl = sl.asReadLock();
+            Lock wl = sl.asWriteLock();
+            for (int i = 0; i < 2; i++) {
+                rl.lock();
+                try {
+                    check(sl.isReadLocked());
+                    check(!sl.isWriteLocked());
+                    check(sl.tryWriteLock() == 0L);
+                    check(sl.tryWriteLock(1L, SECONDS) == 0L);
+                } finally {
+                    rl.unlock();
+                }
+                check(!sl.isReadLocked());
+                check(!sl.isWriteLocked());
+
+                wl.lock();
+                try {
+                    check(!sl.isReadLocked());
+                    check(sl.isWriteLocked());
+                    check(sl.tryWriteLock() == 0L);
+                    check(sl.tryWriteLock(1L, SECONDS) == 0L);
+                } finally {
+                    wl.unlock();
+                }
+                check(!sl.isReadLocked());
+                check(!sl.isWriteLocked());
+
+                ReadWriteLock rwl = sl.asReadWriteLock();
+                rl = rwl.readLock();
+                wl = rwl.writeLock();
+            }
+        } catch (Throwable t) { unexpected(t); }
+    }
+
+    //--------------------- Infrastructure ---------------------------
+    static volatile int passed = 0, failed = 0;
+    static void pass() {passed++;}
+    static void fail() {failed++; Thread.dumpStack();}
+    static void fail(String msg) {System.out.println(msg); fail();}
+    static void unexpected(Throwable t) {failed++; t.printStackTrace();}
+    static void check(boolean cond) {if (cond) pass(); else fail();}
+    static void equal(Object x, Object y) {
+        if (x == null ? y == null : x.equals(y)) pass();
+        else fail(x + " not equal to " + y);}
+    public static void main(String[] args) throws Throwable {
+        try {realMain(args);} catch (Throwable t) {unexpected(t);}
+        System.out.printf("%nPassed = %d, failed = %d%n%n", passed, failed);
+        if (failed > 0) throw new AssertionError("Some tests failed");}
+}