From 3d4ae360746c7f95b42a685d1254e69d0f0061f4 Mon Sep 17 00:00:00 2001
From: Kun Zhang <zhangkun@google.com>
Date: Mon, 12 Sep 2016 09:58:46 -0700
Subject: [PATCH] Fix a deadlock in TransportSet.

Honor the lock order that transport lock > channel lock.

Resolves #2246
---
 core/src/main/java/io/grpc/internal/TransportSet.java | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/core/src/main/java/io/grpc/internal/TransportSet.java b/core/src/main/java/io/grpc/internal/TransportSet.java
index 025b83276f..d89a8ac49c 100644
--- a/core/src/main/java/io/grpc/internal/TransportSet.java
+++ b/core/src/main/java/io/grpc/internal/TransportSet.java
@@ -249,9 +249,14 @@ final class TransportSet implements WithLogId {
           delayedTransport.endBackoff();
           boolean shutdownDelayedTransport = false;
           Runnable runnable = null;
+          // TransportSet as a channel layer class should not call into transport methods while
+          // holding the lock, thus we call hasPendingStreams() outside of the lock.  It will cause
+          // a _benign_ race where the TransportSet may transition to CONNECTING when there is not
+          // pending stream.
+          boolean hasPendingStreams = delayedTransport.hasPendingStreams();
           synchronized (lock) {
             reconnectTask = null;
-            if (delayedTransport.hasPendingStreams()) {
+            if (hasPendingStreams) {
               // Transition directly to CONNECTING
               runnable = startNewTransport(delayedTransport);
             } else {