changeset 15020:50394fa17c1b

8006007: j.u.c.atomic classes should use intrinsic getAndXXX provided by 7023898 Reviewed-by: dl, shade
author chegar
date Thu, 10 Jan 2013 21:52:38 +0000
parents fb36233a54d9
children 24d25ecda7ce e4468ffbb9b4 9639ef45ef3e
files jdk/src/share/classes/java/util/concurrent/atomic/AtomicBoolean.java jdk/src/share/classes/java/util/concurrent/atomic/AtomicInteger.java jdk/src/share/classes/java/util/concurrent/atomic/AtomicIntegerArray.java jdk/src/share/classes/java/util/concurrent/atomic/AtomicIntegerFieldUpdater.java jdk/src/share/classes/java/util/concurrent/atomic/AtomicLong.java jdk/src/share/classes/java/util/concurrent/atomic/AtomicLongArray.java jdk/src/share/classes/java/util/concurrent/atomic/AtomicLongFieldUpdater.java jdk/src/share/classes/java/util/concurrent/atomic/AtomicReference.java jdk/src/share/classes/java/util/concurrent/atomic/AtomicReferenceArray.java jdk/src/share/classes/java/util/concurrent/atomic/AtomicReferenceFieldUpdater.java
diffstat 10 files changed, 204 insertions(+), 242 deletions(-) [+]
line wrap: on
line diff
--- a/jdk/src/share/classes/java/util/concurrent/atomic/AtomicBoolean.java	Thu Jan 10 15:09:45 2013 -0500
+++ b/jdk/src/share/classes/java/util/concurrent/atomic/AtomicBoolean.java	Thu Jan 10 21:52:38 2013 +0000
@@ -111,7 +111,7 @@
      *
      * @param expect the expected value
      * @param update the new value
-     * @return true if successful.
+     * @return true if successful
      */
     public boolean weakCompareAndSet(boolean expect, boolean update) {
         int e = expect ? 1 : 0;
@@ -146,16 +146,16 @@
      * @return the previous value
      */
     public final boolean getAndSet(boolean newValue) {
-        for (;;) {
-            boolean current = get();
-            if (compareAndSet(current, newValue))
-                return current;
-        }
+        boolean prev;
+        do {
+            prev = get();
+        } while (!compareAndSet(prev, newValue));
+        return prev;
     }
 
     /**
      * Returns the String representation of the current value.
-     * @return the String representation of the current value.
+     * @return the String representation of the current value
      */
     public String toString() {
         return Boolean.toString(get());
--- a/jdk/src/share/classes/java/util/concurrent/atomic/AtomicInteger.java	Thu Jan 10 15:09:45 2013 -0500
+++ b/jdk/src/share/classes/java/util/concurrent/atomic/AtomicInteger.java	Thu Jan 10 21:52:38 2013 +0000
@@ -115,11 +115,7 @@
      * @return the previous value
      */
     public final int getAndSet(int newValue) {
-        for (;;) {
-            int current = get();
-            if (compareAndSet(current, newValue))
-                return current;
-        }
+        return unsafe.getAndSetInt(this, valueOffset, newValue);
     }
 
     /**
@@ -145,7 +141,7 @@
      *
      * @param expect the expected value
      * @param update the new value
-     * @return true if successful.
+     * @return true if successful
      */
     public final boolean weakCompareAndSet(int expect, int update) {
         return unsafe.compareAndSwapInt(this, valueOffset, expect, update);
@@ -157,12 +153,7 @@
      * @return the previous value
      */
     public final int getAndIncrement() {
-        for (;;) {
-            int current = get();
-            int next = current + 1;
-            if (compareAndSet(current, next))
-                return current;
-        }
+        return getAndAdd(1);
     }
 
     /**
@@ -171,12 +162,7 @@
      * @return the previous value
      */
     public final int getAndDecrement() {
-        for (;;) {
-            int current = get();
-            int next = current - 1;
-            if (compareAndSet(current, next))
-                return current;
-        }
+        return getAndAdd(-1);
     }
 
     /**
@@ -186,12 +172,7 @@
      * @return the previous value
      */
     public final int getAndAdd(int delta) {
-        for (;;) {
-            int current = get();
-            int next = current + delta;
-            if (compareAndSet(current, next))
-                return current;
-        }
+        return unsafe.getAndAddInt(this, valueOffset, delta);
     }
 
     /**
@@ -200,12 +181,7 @@
      * @return the updated value
      */
     public final int incrementAndGet() {
-        for (;;) {
-            int current = get();
-            int next = current + 1;
-            if (compareAndSet(current, next))
-                return next;
-        }
+        return getAndAdd(1) + 1;
     }
 
     /**
@@ -214,12 +190,7 @@
      * @return the updated value
      */
     public final int decrementAndGet() {
-        for (;;) {
-            int current = get();
-            int next = current - 1;
-            if (compareAndSet(current, next))
-                return next;
-        }
+        return getAndAdd(-1) - 1;
     }
 
     /**
@@ -229,17 +200,12 @@
      * @return the updated value
      */
     public final int addAndGet(int delta) {
-        for (;;) {
-            int current = get();
-            int next = current + delta;
-            if (compareAndSet(current, next))
-                return next;
-        }
+        return getAndAdd(delta) + delta;
     }
 
     /**
      * Returns the String representation of the current value.
-     * @return the String representation of the current value.
+     * @return the String representation of the current value
      */
     public String toString() {
         return Integer.toString(get());
--- a/jdk/src/share/classes/java/util/concurrent/atomic/AtomicIntegerArray.java	Thu Jan 10 15:09:45 2013 -0500
+++ b/jdk/src/share/classes/java/util/concurrent/atomic/AtomicIntegerArray.java	Thu Jan 10 21:52:38 2013 +0000
@@ -145,12 +145,7 @@
      * @return the previous value
      */
     public final int getAndSet(int i, int newValue) {
-        long offset = checkedByteOffset(i);
-        while (true) {
-            int current = getRaw(offset);
-            if (compareAndSetRaw(offset, current, newValue))
-                return current;
-        }
+        return unsafe.getAndSetInt(array, checkedByteOffset(i), newValue);
     }
 
     /**
@@ -182,7 +177,7 @@
      * @param i the index
      * @param expect the expected value
      * @param update the new value
-     * @return true if successful.
+     * @return true if successful
      */
     public final boolean weakCompareAndSet(int i, int expect, int update) {
         return compareAndSet(i, expect, update);
@@ -216,12 +211,7 @@
      * @return the previous value
      */
     public final int getAndAdd(int i, int delta) {
-        long offset = checkedByteOffset(i);
-        while (true) {
-            int current = getRaw(offset);
-            if (compareAndSetRaw(offset, current, current + delta))
-                return current;
-        }
+        return unsafe.getAndAddInt(array, checkedByteOffset(i), delta);
     }
 
     /**
@@ -231,7 +221,7 @@
      * @return the updated value
      */
     public final int incrementAndGet(int i) {
-        return addAndGet(i, 1);
+        return getAndAdd(i, 1) + 1;
     }
 
     /**
@@ -241,7 +231,7 @@
      * @return the updated value
      */
     public final int decrementAndGet(int i) {
-        return addAndGet(i, -1);
+        return getAndAdd(i, -1) - 1;
     }
 
     /**
@@ -252,13 +242,7 @@
      * @return the updated value
      */
     public final int addAndGet(int i, int delta) {
-        long offset = checkedByteOffset(i);
-        while (true) {
-            int current = getRaw(offset);
-            int next = current + delta;
-            if (compareAndSetRaw(offset, current, next))
-                return next;
-        }
+        return getAndAdd(i, delta) + delta;
     }
 
     /**
--- a/jdk/src/share/classes/java/util/concurrent/atomic/AtomicIntegerFieldUpdater.java	Thu Jan 10 15:09:45 2013 -0500
+++ b/jdk/src/share/classes/java/util/concurrent/atomic/AtomicIntegerFieldUpdater.java	Thu Jan 10 21:52:38 2013 +0000
@@ -159,11 +159,11 @@
      * @return the previous value
      */
     public int getAndSet(T obj, int newValue) {
-        for (;;) {
-            int current = get(obj);
-            if (compareAndSet(obj, current, newValue))
-                return current;
-        }
+        int prev;
+        do {
+            prev = get(obj);
+        } while (!compareAndSet(obj, prev, newValue));
+        return prev;
     }
 
     /**
@@ -174,12 +174,12 @@
      * @return the previous value
      */
     public int getAndIncrement(T obj) {
-        for (;;) {
-            int current = get(obj);
-            int next = current + 1;
-            if (compareAndSet(obj, current, next))
-                return current;
-        }
+        int prev, next;
+        do {
+            prev = get(obj);
+            next = prev + 1;
+        } while (!compareAndSet(obj, prev, next));
+        return prev;
     }
 
     /**
@@ -190,12 +190,12 @@
      * @return the previous value
      */
     public int getAndDecrement(T obj) {
-        for (;;) {
-            int current = get(obj);
-            int next = current - 1;
-            if (compareAndSet(obj, current, next))
-                return current;
-        }
+        int prev, next;
+        do {
+            prev = get(obj);
+            next = prev - 1;
+        } while (!compareAndSet(obj, prev, next));
+        return prev;
     }
 
     /**
@@ -207,12 +207,12 @@
      * @return the previous value
      */
     public int getAndAdd(T obj, int delta) {
-        for (;;) {
-            int current = get(obj);
-            int next = current + delta;
-            if (compareAndSet(obj, current, next))
-                return current;
-        }
+        int prev, next;
+        do {
+            prev = get(obj);
+            next = prev + delta;
+        } while (!compareAndSet(obj, prev, next));
+        return prev;
     }
 
     /**
@@ -223,12 +223,12 @@
      * @return the updated value
      */
     public int incrementAndGet(T obj) {
-        for (;;) {
-            int current = get(obj);
-            int next = current + 1;
-            if (compareAndSet(obj, current, next))
-                return next;
-        }
+        int prev, next;
+        do {
+            prev = get(obj);
+            next = prev + 1;
+        } while (!compareAndSet(obj, prev, next));
+        return next;
     }
 
     /**
@@ -239,12 +239,12 @@
      * @return the updated value
      */
     public int decrementAndGet(T obj) {
-        for (;;) {
-            int current = get(obj);
-            int next = current - 1;
-            if (compareAndSet(obj, current, next))
-                return next;
-        }
+        int prev, next;
+        do {
+            prev = get(obj);
+            next = prev - 1;
+        } while (!compareAndSet(obj, prev, next));
+        return next;
     }
 
     /**
@@ -256,12 +256,12 @@
      * @return the updated value
      */
     public int addAndGet(T obj, int delta) {
-        for (;;) {
-            int current = get(obj);
-            int next = current + delta;
-            if (compareAndSet(obj, current, next))
-                return next;
-        }
+        int prev, next;
+        do {
+            prev = get(obj);
+            next = prev + delta;
+        } while (!compareAndSet(obj, prev, next));
+        return next;
     }
 
     /**
@@ -361,6 +361,36 @@
             return unsafe.getIntVolatile(obj, offset);
         }
 
+        public int getAndSet(T obj, int newValue) {
+            if (obj == null || obj.getClass() != tclass || cclass != null) fullCheck(obj);
+            return unsafe.getAndSetInt(obj, offset, newValue);
+        }
+
+        public int getAndIncrement(T obj) {
+            return getAndAdd(obj, 1);
+        }
+
+        public int getAndDecrement(T obj) {
+            return getAndAdd(obj, -1);
+        }
+
+        public int getAndAdd(T obj, int delta) {
+            if (obj == null || obj.getClass() != tclass || cclass != null) fullCheck(obj);
+            return unsafe.getAndAddInt(obj, offset, delta);
+        }
+
+        public int incrementAndGet(T obj) {
+            return getAndAdd(obj, 1) + 1;
+        }
+
+        public int decrementAndGet(T obj) {
+             return getAndAdd(obj, -1) - 1;
+        }
+
+        public int addAndGet(T obj, int delta) {
+            return getAndAdd(obj, delta) + delta;
+        }
+
         private void ensureProtectedAccess(T obj) {
             if (cclass.isInstance(obj)) {
                 return;
--- a/jdk/src/share/classes/java/util/concurrent/atomic/AtomicLong.java	Thu Jan 10 15:09:45 2013 -0500
+++ b/jdk/src/share/classes/java/util/concurrent/atomic/AtomicLong.java	Thu Jan 10 21:52:38 2013 +0000
@@ -129,11 +129,7 @@
      * @return the previous value
      */
     public final long getAndSet(long newValue) {
-        while (true) {
-            long current = get();
-            if (compareAndSet(current, newValue))
-                return current;
-        }
+        return unsafe.getAndSetLong(this, valueOffset, newValue);
     }
 
     /**
@@ -159,7 +155,7 @@
      *
      * @param expect the expected value
      * @param update the new value
-     * @return true if successful.
+     * @return true if successful
      */
     public final boolean weakCompareAndSet(long expect, long update) {
         return unsafe.compareAndSwapLong(this, valueOffset, expect, update);
@@ -171,12 +167,7 @@
      * @return the previous value
      */
     public final long getAndIncrement() {
-        while (true) {
-            long current = get();
-            long next = current + 1;
-            if (compareAndSet(current, next))
-                return current;
-        }
+        return getAndAdd(1);
     }
 
     /**
@@ -185,12 +176,7 @@
      * @return the previous value
      */
     public final long getAndDecrement() {
-        while (true) {
-            long current = get();
-            long next = current - 1;
-            if (compareAndSet(current, next))
-                return current;
-        }
+        return getAndAdd(-1);
     }
 
     /**
@@ -200,12 +186,7 @@
      * @return the previous value
      */
     public final long getAndAdd(long delta) {
-        while (true) {
-            long current = get();
-            long next = current + delta;
-            if (compareAndSet(current, next))
-                return current;
-        }
+        return unsafe.getAndAddLong(this, valueOffset, delta);
     }
 
     /**
@@ -214,12 +195,7 @@
      * @return the updated value
      */
     public final long incrementAndGet() {
-        for (;;) {
-            long current = get();
-            long next = current + 1;
-            if (compareAndSet(current, next))
-                return next;
-        }
+        return getAndAdd(1) + 1;
     }
 
     /**
@@ -228,12 +204,7 @@
      * @return the updated value
      */
     public final long decrementAndGet() {
-        for (;;) {
-            long current = get();
-            long next = current - 1;
-            if (compareAndSet(current, next))
-                return next;
-        }
+        return getAndAdd(-1) - 1;
     }
 
     /**
@@ -243,17 +214,12 @@
      * @return the updated value
      */
     public final long addAndGet(long delta) {
-        for (;;) {
-            long current = get();
-            long next = current + delta;
-            if (compareAndSet(current, next))
-                return next;
-        }
+        return getAndAdd(delta) + delta;
     }
 
     /**
      * Returns the String representation of the current value.
-     * @return the String representation of the current value.
+     * @return the String representation of the current value
      */
     public String toString() {
         return Long.toString(get());
--- a/jdk/src/share/classes/java/util/concurrent/atomic/AtomicLongArray.java	Thu Jan 10 15:09:45 2013 -0500
+++ b/jdk/src/share/classes/java/util/concurrent/atomic/AtomicLongArray.java	Thu Jan 10 21:52:38 2013 +0000
@@ -144,12 +144,7 @@
      * @return the previous value
      */
     public final long getAndSet(int i, long newValue) {
-        long offset = checkedByteOffset(i);
-        while (true) {
-            long current = getRaw(offset);
-            if (compareAndSetRaw(offset, current, newValue))
-                return current;
-        }
+        return unsafe.getAndSetLong(array, checkedByteOffset(i), newValue);
     }
 
     /**
@@ -181,7 +176,7 @@
      * @param i the index
      * @param expect the expected value
      * @param update the new value
-     * @return true if successful.
+     * @return true if successful
      */
     public final boolean weakCompareAndSet(int i, long expect, long update) {
         return compareAndSet(i, expect, update);
@@ -215,12 +210,7 @@
      * @return the previous value
      */
     public final long getAndAdd(int i, long delta) {
-        long offset = checkedByteOffset(i);
-        while (true) {
-            long current = getRaw(offset);
-            if (compareAndSetRaw(offset, current, current + delta))
-                return current;
-        }
+        return unsafe.getAndAddLong(array, checkedByteOffset(i), delta);
     }
 
     /**
@@ -230,7 +220,7 @@
      * @return the updated value
      */
     public final long incrementAndGet(int i) {
-        return addAndGet(i, 1);
+        return getAndAdd(i, 1) + 1;
     }
 
     /**
@@ -240,7 +230,7 @@
      * @return the updated value
      */
     public final long decrementAndGet(int i) {
-        return addAndGet(i, -1);
+        return getAndAdd(i, -1) - 1;
     }
 
     /**
@@ -251,13 +241,7 @@
      * @return the updated value
      */
     public long addAndGet(int i, long delta) {
-        long offset = checkedByteOffset(i);
-        while (true) {
-            long current = getRaw(offset);
-            long next = current + delta;
-            if (compareAndSetRaw(offset, current, next))
-                return next;
-        }
+        return getAndAdd(i, delta) + delta;
     }
 
     /**
--- a/jdk/src/share/classes/java/util/concurrent/atomic/AtomicLongFieldUpdater.java	Thu Jan 10 15:09:45 2013 -0500
+++ b/jdk/src/share/classes/java/util/concurrent/atomic/AtomicLongFieldUpdater.java	Thu Jan 10 21:52:38 2013 +0000
@@ -98,7 +98,7 @@
      * @param obj An object whose field to conditionally set
      * @param expect the expected value
      * @param update the new value
-     * @return true if successful.
+     * @return true if successful
      * @throws ClassCastException if {@code obj} is not an instance
      * of the class possessing the field established in the constructor.
      */
@@ -118,7 +118,7 @@
      * @param obj An object whose field to conditionally set
      * @param expect the expected value
      * @param update the new value
-     * @return true if successful.
+     * @return true if successful
      * @throws ClassCastException if {@code obj} is not an instance
      * of the class possessing the field established in the constructor.
      */
@@ -162,11 +162,11 @@
      * @return the previous value
      */
     public long getAndSet(T obj, long newValue) {
-        for (;;) {
-            long current = get(obj);
-            if (compareAndSet(obj, current, newValue))
-                return current;
-        }
+        long prev;
+        do {
+            prev = get(obj);
+        } while (!compareAndSet(obj, prev, newValue));
+        return prev;
     }
 
     /**
@@ -177,12 +177,12 @@
      * @return the previous value
      */
     public long getAndIncrement(T obj) {
-        for (;;) {
-            long current = get(obj);
-            long next = current + 1;
-            if (compareAndSet(obj, current, next))
-                return current;
-        }
+        long prev, next;
+        do {
+            prev = get(obj);
+            next = prev + 1;
+        } while (!compareAndSet(obj, prev, next));
+        return prev;
     }
 
     /**
@@ -193,12 +193,12 @@
      * @return the previous value
      */
     public long getAndDecrement(T obj) {
-        for (;;) {
-            long current = get(obj);
-            long next = current - 1;
-            if (compareAndSet(obj, current, next))
-                return current;
-        }
+        long prev, next;
+        do {
+            prev = get(obj);
+            next = prev - 1;
+        } while (!compareAndSet(obj, prev, next));
+        return prev;
     }
 
     /**
@@ -210,12 +210,12 @@
      * @return the previous value
      */
     public long getAndAdd(T obj, long delta) {
-        for (;;) {
-            long current = get(obj);
-            long next = current + delta;
-            if (compareAndSet(obj, current, next))
-                return current;
-        }
+        long prev, next;
+        do {
+            prev = get(obj);
+            next = prev + delta;
+        } while (!compareAndSet(obj, prev, next));
+        return prev;
     }
 
     /**
@@ -226,12 +226,12 @@
      * @return the updated value
      */
     public long incrementAndGet(T obj) {
-        for (;;) {
-            long current = get(obj);
-            long next = current + 1;
-            if (compareAndSet(obj, current, next))
-                return next;
-        }
+        long prev, next;
+        do {
+            prev = get(obj);
+            next = prev + 1;
+        } while (!compareAndSet(obj, prev, next));
+        return next;
     }
 
     /**
@@ -242,12 +242,12 @@
      * @return the updated value
      */
     public long decrementAndGet(T obj) {
-        for (;;) {
-            long current = get(obj);
-            long next = current - 1;
-            if (compareAndSet(obj, current, next))
-                return next;
-        }
+        long prev, next;
+        do {
+            prev = get(obj);
+            next = prev - 1;
+        } while (!compareAndSet(obj, prev, next));
+        return next;
     }
 
     /**
@@ -259,12 +259,12 @@
      * @return the updated value
      */
     public long addAndGet(T obj, long delta) {
-        for (;;) {
-            long current = get(obj);
-            long next = current + delta;
-            if (compareAndSet(obj, current, next))
-                return next;
-        }
+        long prev, next;
+        do {
+            prev = get(obj);
+            next = prev + delta;
+        } while (!compareAndSet(obj, prev, next));
+        return next;
     }
 
     private static class CASUpdater<T> extends AtomicLongFieldUpdater<T> {
@@ -345,6 +345,36 @@
             return unsafe.getLongVolatile(obj, offset);
         }
 
+        public long getAndSet(T obj, long newValue) {
+            if (obj == null || obj.getClass() != tclass || cclass != null) fullCheck(obj);
+            return unsafe.getAndSetLong(obj, offset, newValue);
+        }
+
+        public long getAndIncrement(T obj) {
+            return getAndAdd(obj, 1);
+        }
+
+        public long getAndDecrement(T obj) {
+            return getAndAdd(obj, -1);
+        }
+
+        public long getAndAdd(T obj, long delta) {
+            if (obj == null || obj.getClass() != tclass || cclass != null) fullCheck(obj);
+            return unsafe.getAndAddLong(obj, offset, delta);
+        }
+
+        public long incrementAndGet(T obj) {
+            return getAndAdd(obj, 1) + 1;
+        }
+
+        public long decrementAndGet(T obj) {
+             return getAndAdd(obj, -1) - 1;
+        }
+
+        public long addAndGet(T obj, long delta) {
+            return getAndAdd(obj, delta) + delta;
+        }
+
         private void ensureProtectedAccess(T obj) {
             if (cclass.isInstance(obj)) {
                 return;
--- a/jdk/src/share/classes/java/util/concurrent/atomic/AtomicReference.java	Thu Jan 10 15:09:45 2013 -0500
+++ b/jdk/src/share/classes/java/util/concurrent/atomic/AtomicReference.java	Thu Jan 10 21:52:38 2013 +0000
@@ -124,7 +124,7 @@
      *
      * @param expect the expected value
      * @param update the new value
-     * @return true if successful.
+     * @return true if successful
      */
     public final boolean weakCompareAndSet(V expect, V update) {
         return unsafe.compareAndSwapObject(this, valueOffset, expect, update);
@@ -136,17 +136,14 @@
      * @param newValue the new value
      * @return the previous value
      */
+    @SuppressWarnings("unchecked")
     public final V getAndSet(V newValue) {
-        while (true) {
-            V x = get();
-            if (compareAndSet(x, newValue))
-                return x;
-        }
+        return (V)unsafe.getAndSetObject(this, valueOffset, newValue);
     }
 
     /**
      * Returns the String representation of the current value.
-     * @return the String representation of the current value.
+     * @return the String representation of the current value
      */
     public String toString() {
         return String.valueOf(get());
--- a/jdk/src/share/classes/java/util/concurrent/atomic/AtomicReferenceArray.java	Thu Jan 10 15:09:45 2013 -0500
+++ b/jdk/src/share/classes/java/util/concurrent/atomic/AtomicReferenceArray.java	Thu Jan 10 21:52:38 2013 +0000
@@ -159,13 +159,9 @@
      * @param newValue the new value
      * @return the previous value
      */
+    @SuppressWarnings("unchecked")
     public final E getAndSet(int i, E newValue) {
-        long offset = checkedByteOffset(i);
-        while (true) {
-            E current = getRaw(offset);
-            if (compareAndSetRaw(offset, current, newValue))
-                return current;
-        }
+        return (E)unsafe.getAndSetObject(array, checkedByteOffset(i), newValue);
     }
 
     /**
@@ -197,7 +193,7 @@
      * @param i the index
      * @param expect the expected value
      * @param update the new value
-     * @return true if successful.
+     * @return true if successful
      */
     public final boolean weakCompareAndSet(int i, E expect, E update) {
         return compareAndSet(i, expect, update);
--- a/jdk/src/share/classes/java/util/concurrent/atomic/AtomicReferenceFieldUpdater.java	Thu Jan 10 15:09:45 2013 -0500
+++ b/jdk/src/share/classes/java/util/concurrent/atomic/AtomicReferenceFieldUpdater.java	Thu Jan 10 21:52:38 2013 +0000
@@ -116,7 +116,7 @@
      * @param obj An object whose field to conditionally set
      * @param expect the expected value
      * @param update the new value
-     * @return true if successful.
+     * @return true if successful
      */
     public abstract boolean compareAndSet(T obj, V expect, V update);
 
@@ -134,7 +134,7 @@
      * @param obj An object whose field to conditionally set
      * @param expect the expected value
      * @param update the new value
-     * @return true if successful.
+     * @return true if successful
      */
     public abstract boolean weakCompareAndSet(T obj, V expect, V update);
 
@@ -176,11 +176,11 @@
      * @return the previous value
      */
     public V getAndSet(T obj, V newValue) {
-        for (;;) {
-            V current = get(obj);
-            if (compareAndSet(obj, current, newValue))
-                return current;
-        }
+        V prev;
+        do {
+            prev = get(obj);
+        } while (!compareAndSet(obj, prev, newValue));
+        return prev;
     }
 
     private static final class AtomicReferenceFieldUpdaterImpl<T,V>
@@ -321,6 +321,15 @@
             return (V)unsafe.getObjectVolatile(obj, offset);
         }
 
+        @SuppressWarnings("unchecked")
+        public V getAndSet(T obj, V newValue) {
+            if (obj == null || obj.getClass() != tclass || cclass != null ||
+                (newValue != null && vclass != null &&
+                 vclass != newValue.getClass()))
+                updateCheck(obj, newValue);
+            return (V)unsafe.getAndSetObject(obj, offset, newValue);
+        }
+
         private void ensureProtectedAccess(T obj) {
             if (cclass.isInstance(obj)) {
                 return;