Remove Intrinsic locking in ChannelImpl.

core/src/main/java/io/grpc/ChannelImpl.java

@@ -62,6 +62,7 @@ public final class ChannelImpl extends Channel {
   private final ClientTransportFactory transportFactory;
   private final ExecutorService executor;
   private final String userAgent;
+  private final Object lock = new Object();
 
   /**
    * Executor that runs deadline timers for requests.
@@ -77,16 +78,16 @@ public final class ChannelImpl extends Channel {
    * present, but previously used transports that still have streams or are stopping may also be
    * present.
    */
-  @GuardedBy("this")
+  @GuardedBy("lock")
   private Collection<ClientTransport> transports = new ArrayList<ClientTransport>();
   /**
    * The transport for new outgoing requests. 'this' lock must be held when assigning to
    * activeTransport.
    */
   private volatile ClientTransport activeTransport;
-  @GuardedBy("this")
+  @GuardedBy("lock")
   private boolean shutdown;
-  @GuardedBy("this")
+  @GuardedBy("lock")
   private boolean terminated;
   private Runnable terminationRunnable;
 
@@ -116,7 +117,8 @@ public final class ChannelImpl extends Channel {
    * Initiates an orderly shutdown in which preexisting calls continue but new calls are immediately
    * cancelled.
    */
-  public synchronized ChannelImpl shutdown() {
+  public ChannelImpl shutdown() {
+    synchronized (lock) {
       if (shutdown) {
         return this;
       }
@@ -129,13 +131,14 @@ public final class ChannelImpl extends Channel {
         activeTransport = null;
       } else if (transports.isEmpty()) {
         terminated = true;
-      notifyAll();
+        lock.notifyAll();
         if (terminationRunnable != null) {
           terminationRunnable.run();
         }
       }
       return this;
     }
+  }
 
   /**
    * Initiates a forceful shutdown in which preexisting and new calls are cancelled. Although
@@ -145,10 +148,12 @@ public final class ChannelImpl extends Channel {
    * <p>NOT YET IMPLEMENTED. This method currently behaves identically to shutdown().
    */
   // TODO(ejona86): cancel preexisting calls.
-  public synchronized ChannelImpl shutdownNow() {
+  public ChannelImpl shutdownNow() {
+    synchronized (lock) {
       shutdown();
       return this;
     }
+  }
 
   /**
    * Returns whether the channel is shutdown. Shutdown channels immediately cancel any new calls,
@@ -157,24 +162,27 @@ public final class ChannelImpl extends Channel {
    * @see #shutdown()
    * @see #isTerminated()
    */
-  public synchronized boolean isShutdown() {
+  public boolean isShutdown() {
+    synchronized (lock) {
       return shutdown;
     }
+  }
 
   /**
    * Waits for the channel to become terminated, giving up if the timeout is reached.
    *
    * @return whether the channel is terminated, as would be done by {@link #isTerminated()}.
    */
-  public synchronized boolean awaitTerminated(long timeout, TimeUnit unit)
-      throws InterruptedException {
+  public boolean awaitTerminated(long timeout, TimeUnit unit) throws InterruptedException {
+    synchronized (lock) {
       long timeoutNanos = unit.toNanos(timeout);
       long endTimeNanos = System.nanoTime() + timeoutNanos;
       while (!terminated && (timeoutNanos = endTimeNanos - System.nanoTime()) > 0) {
-      TimeUnit.NANOSECONDS.timedWait(this, timeoutNanos);
+        TimeUnit.NANOSECONDS.timedWait(lock, timeoutNanos);
       }
       return terminated;
     }
+  }
 
   /**
    * Returns whether the channel is terminated. Terminated channels have no running calls and
@@ -182,9 +190,11 @@ public final class ChannelImpl extends Channel {
    *
    * @see #isShutdown()
    */
-  public synchronized boolean isTerminated() {
+  public boolean isTerminated() {
+    synchronized (lock) {
       return terminated;
     }
+  }
 
   /**
    * Pings the remote endpoint to verify that the transport is still active. When an acknowledgement
@@ -224,7 +234,7 @@ public final class ChannelImpl extends Channel {
     if (savedActiveTransport != null) {
       return savedActiveTransport;
     }
-    synchronized (this) {
+    synchronized (lock) {
       if (shutdown) {
         return null;
       }
@@ -277,7 +287,7 @@ public final class ChannelImpl extends Channel {
 
     @Override
     public void transportShutdown() {
-      synchronized (ChannelImpl.this) {
+      synchronized (lock) {
         if (activeTransport == transport) {
           activeTransport = null;
         }
@@ -286,7 +296,7 @@ public final class ChannelImpl extends Channel {
 
     @Override
     public void transportTerminated() {
-      synchronized (ChannelImpl.this) {
+      synchronized (lock) {
         if (activeTransport == transport) {
           log.warning("transportTerminated called without previous transportShutdown");
           activeTransport = null;
@@ -298,7 +308,7 @@ public final class ChannelImpl extends Channel {
             log.warning("transportTerminated called after already terminated");
           }
           terminated = true;
-          ChannelImpl.this.notifyAll();
+          lock.notifyAll();
           if (terminationRunnable != null) {
             terminationRunnable.run();
           }