Fixes JCTools#308: Remove useless fences on chunk's prev field accesses

franz1981 · Jun 1, 2020 · cae3e01 · cae3e01
1 parent c0b570d
commit cae3e01
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Showing 2 changed files with 9 additions and 10 deletions.
diff --git a/jctools-core/src/main/java/org/jctools/queues/MpUnboundedXaddArrayQueue.java b/jctools-core/src/main/java/org/jctools/queues/MpUnboundedXaddArrayQueue.java
@@ -308,7 +308,7 @@ final R producerChunkForIndex(
         {
             // prev cannot be null, because the consumer cannot null it without consuming the element for which we are
             // trying to get the chunk.
-            currentChunk = currentChunk.lvPrev();
+            currentChunk = currentChunk.lpPrev();
             assert currentChunk != null;
         }
         assert currentChunk.lvIndex() == requiredChunkIndex;
@@ -355,7 +355,7 @@ private R newOrPooledChunk(R prevChunk, long nextChunkIndex)
         {
             // single-writer: prevChunk::index == nextChunkIndex is protecting it
             assert newChunk.lvIndex() < prevChunk.lvIndex();
-            newChunk.soPrev(prevChunk);
+            newChunk.spPrev(prevChunk);
             // index set is releasing prev, allowing other pending offers to continue
             newChunk.soIndex(nextChunkIndex);
         }
@@ -374,7 +374,7 @@ final void moveToNextConsumerChunk(R cChunk, R next)
     {
         // avoid GC nepotism
         cChunk.soNext(null);
-        next.soPrev(null);
+        next.spPrev(null);
         // no need to cChunk.soIndex(NOT_USED)
         if (cChunk.isPooled())
         {

diff --git a/jctools-core/src/main/java/org/jctools/queues/MpUnboundedXaddChunk.java b/jctools-core/src/main/java/org/jctools/queues/MpUnboundedXaddChunk.java
@@ -11,21 +11,20 @@ class MpUnboundedXaddChunk<R,E>
 {
     final static int NOT_USED = -1;
 
-    private static final long PREV_OFFSET = fieldOffset(MpUnboundedXaddChunk.class, "prev");
     private static final long NEXT_OFFSET = fieldOffset(MpUnboundedXaddChunk.class, "next");
     private static final long INDEX_OFFSET = fieldOffset(MpUnboundedXaddChunk.class, "index");
 
     private final boolean pooled;
     private final E[] buffer;
 
-    private volatile R prev;
+    private R prev;
     private volatile long index;
     private volatile R next;
     MpUnboundedXaddChunk(long index, R prev, int size, boolean pooled)
     {
         buffer = allocateRefArray(size);
         // next is null
-        soPrev(prev);
+        spPrev(prev);
         spIndex(index);
         this.pooled = pooled;
     }
@@ -60,14 +59,14 @@ final void soNext(R value)
         UNSAFE.putOrderedObject(this, NEXT_OFFSET, value);
     }
 
-    final R lvPrev()
+    final R lpPrev()
     {
-        return prev;
+        return this.prev;
     }
 
-    final void soPrev(R value)
+    final void spPrev(R value)
     {
-        UNSAFE.putObject(this, PREV_OFFSET, value);
+        this.prev = value;
     }
 
     final void soElement(int index, E e)