8345181: (ch) Windows asynchronous channels may return temporary direct buffers to the buffer cache twice (win)

Reviewed-by: alanb, michaelm

Author: Brian Burkhalter

src/java.base/windows/classes/sun/nio/ch/WindowsAsynchronousFileChannelImpl.java

@@ -25,6 +25,8 @@
 
 package sun.nio.ch;
 
+import java.lang.invoke.MethodHandles;
+import java.lang.invoke.VarHandle;
 import java.nio.channels.*;
 import java.util.concurrent.*;
 import java.nio.ByteBuffer;
@@ -34,6 +36,7 @@
 import jdk.internal.access.SharedSecrets;
 import jdk.internal.access.JavaIOFileDescriptorAccess;
 import jdk.internal.event.FileForceEvent;
+import jdk.internal.invoke.MhUtil;
 
 /**
  * Windows implementation of AsynchronousFileChannel using overlapped I/O.
@@ -383,10 +386,13 @@ protected void implRelease(FileLockImpl fli) throws IOException {
      * Task that initiates read operation and handles completion result.
      */
     private class ReadTask<A> implements Runnable, Iocp.ResultHandler {
+        private static final VarHandle RELEASED = MhUtil.findVarHandle(MethodHandles.lookup(),
+                "released", boolean.class);
         private final ByteBuffer dst;
         private final int pos, rem;     // buffer position/remaining
         private final long position;    // file position
         private final PendingFuture<Integer,A> result;
+        private volatile boolean released;
 
         // set to dst if direct; otherwise set to substituted direct buffer
         private volatile ByteBuffer buf;
@@ -405,8 +411,9 @@ private class ReadTask<A> implements Runnable, Iocp.ResultHandler {
         }
 
         void releaseBufferIfSubstituted() {
-            if (buf != dst)
+            if (buf != dst && RELEASED.compareAndSet(this, false, true)) {
                 Util.releaseTemporaryDirectBuffer(buf);
+            }
         }
 
         void updatePosition(int bytesTransferred) {
@@ -569,10 +576,13 @@ <A> Future<Integer> implRead(ByteBuffer dst,
      * Task that initiates write operation and handles completion result.
      */
     private class WriteTask<A> implements Runnable, Iocp.ResultHandler {
+        private static final VarHandle RELEASED = MhUtil.findVarHandle(MethodHandles.lookup(),
+                "released", boolean.class);
         private final ByteBuffer src;
         private final int pos, rem;     // buffer position/remaining
         private final long position;    // file position
         private final PendingFuture<Integer,A> result;
+        private volatile boolean released;
 
         // set to src if direct; otherwise set to substituted direct buffer
         private volatile ByteBuffer buf;
@@ -591,8 +601,9 @@ private class WriteTask<A> implements Runnable, Iocp.ResultHandler {
         }
 
         void releaseBufferIfSubstituted() {
-            if (buf != src)
+            if (buf != src && RELEASED.compareAndSet(this, false, true)) {
                 Util.releaseTemporaryDirectBuffer(buf);
+            }
         }
 
         void updatePosition(int bytesTransferred) {

src/java.base/windows/classes/sun/nio/ch/WindowsAsynchronousSocketChannelImpl.java

@@ -25,12 +25,15 @@
 
 package sun.nio.ch;
 
+import java.lang.invoke.MethodHandles;
+import java.lang.invoke.VarHandle;
 import java.nio.channels.*;
 import java.nio.ByteBuffer;
 import java.nio.BufferOverflowException;
 import java.net.*;
 import java.util.concurrent.*;
 import java.io.IOException;
+import jdk.internal.invoke.MhUtil;
 import jdk.internal.misc.Unsafe;
 import sun.net.util.SocketExceptions;
 
@@ -367,10 +370,13 @@ <A> Future<Void> implConnect(SocketAddress remote,
      * result when the read completes.
      */
     private class ReadTask<V,A> implements Runnable, Iocp.ResultHandler {
+        private static final VarHandle RELEASED = MhUtil.findVarHandle(MethodHandles.lookup(),
+                "released", boolean.class);
         private final ByteBuffer[] bufs;
         private final int numBufs;
         private final boolean scatteringRead;
         private final PendingFuture<V,A> result;
+        private volatile boolean released;
 
         // set by run method
         private ByteBuffer[] shadow;
@@ -461,12 +467,14 @@ void updateBuffers(int bytesRead) {
         }
 
         void releaseBuffers() {
-            for (int i=0; i<numBufs; i++) {
-                if (!(bufs[i] instanceof DirectBuffer)) {
-                    Util.releaseTemporaryDirectBuffer(shadow[i]);
+            if (RELEASED.compareAndSet(this, false, true)) {
+                for (int i = 0; i < numBufs; i++) {
+                    if (!(bufs[i] instanceof DirectBuffer)) {
+                        Util.releaseTemporaryDirectBuffer(shadow[i]);
+                    }
                 }
+                IOUtil.releaseScopes(scopeHandleReleasers);
             }
-            IOUtil.releaseScopes(scopeHandleReleasers);
         }
 
         @Override
@@ -641,10 +649,13 @@ public void run() {
      * result when the write completes.
      */
     private class WriteTask<V,A> implements Runnable, Iocp.ResultHandler {
+        private static final VarHandle RELEASED = MhUtil.findVarHandle(MethodHandles.lookup(),
+                "released", boolean.class);
         private final ByteBuffer[] bufs;
         private final int numBufs;
         private final boolean gatheringWrite;
         private final PendingFuture<V,A> result;
+        private volatile boolean released;
 
         // set by run method
         private ByteBuffer[] shadow;
@@ -728,12 +739,14 @@ void updateBuffers(int bytesWritten) {
         }
 
         void releaseBuffers() {
-            for (int i=0; i<numBufs; i++) {
-                if (!(bufs[i] instanceof DirectBuffer)) {
-                    Util.releaseTemporaryDirectBuffer(shadow[i]);
+            if (RELEASED.compareAndSet(this, false, true)) {
+                for (int i = 0; i < numBufs; i++) {
+                    if (!(bufs[i] instanceof DirectBuffer)) {
+                        Util.releaseTemporaryDirectBuffer(shadow[i]);
+                    }
                 }
+                IOUtil.releaseScopes(scopeHandleReleasers);
             }
-            IOUtil.releaseScopes(scopeHandleReleasers);
         }
 
         @Override