From 3d090879c6a3291dadf7cf9a2ffdbc90def2e239 Mon Sep 17 00:00:00 2001
From: Henning Andersen <33268011+henningandersen@users.noreply.github.com>
Date: Mon, 18 Feb 2019 18:10:00 +0100
Subject: [PATCH] Fix potential race during TcpTransport close (#39031)

Fixed two potential causes for leaked threads during tests:
1. When adding a channel to serverChannels, we add it under a monitor
that we do not use when reading from it. This is potentially unsafe if
there is no other happens-before relationship ensuring the safety of
this.
2. Long-shot but if the thread pool was shutdown before entering this
code, we would silently forget about closing server channels so added
assert.

Strengthened the locking to ensure that once we stop the transport, no
new server channels can be made.

Relates to CI failure issue: #37543
---
 .../elasticsearch/transport/TcpTransport.java | 37 ++++++++++---------
 1 file changed, 19 insertions(+), 18 deletions(-)

diff --git a/server/src/main/java/org/elasticsearch/transport/TcpTransport.java b/server/src/main/java/org/elasticsearch/transport/TcpTransport.java
index 2ff5ae1583e37..d5a524105dd01 100644
--- a/server/src/main/java/org/elasticsearch/transport/TcpTransport.java
+++ b/server/src/main/java/org/elasticsearch/transport/TcpTransport.java
@@ -388,28 +388,28 @@ private InetSocketAddress bindToPort(final String name, final InetAddress hostAd
         PortsRange portsRange = new PortsRange(port);
         final AtomicReference<Exception> lastException = new AtomicReference<>();
         final AtomicReference<InetSocketAddress> boundSocket = new AtomicReference<>();
-        boolean success = portsRange.iterate(portNumber -> {
-            try {
-                TcpServerChannel channel = bind(name, new InetSocketAddress(hostAddress, portNumber));
-                synchronized (serverChannels) {
-                    List<TcpServerChannel> list = serverChannels.get(name);
-                    if (list == null) {
-                        list = new ArrayList<>();
-                        serverChannels.put(name, list);
-                    }
-                    list.add(channel);
+        closeLock.writeLock().lock();
+        try {
+            if (lifecycle.initialized() == false && lifecycle.started() == false) {
+                throw new IllegalStateException("transport has been stopped");
+            }
+            boolean success = portsRange.iterate(portNumber -> {
+                try {
+                    TcpServerChannel channel = bind(name, new InetSocketAddress(hostAddress, portNumber));
+                    serverChannels.computeIfAbsent(name, k -> new ArrayList<>()).add(channel);
                     boundSocket.set(channel.getLocalAddress());
+                } catch (Exception e) {
+                    lastException.set(e);
+                    return false;
                 }
-            } catch (Exception e) {
-                lastException.set(e);
-                return false;
+                return true;
+            });
+            if (!success) {
+                throw new BindTransportException("Failed to bind to [" + port + "]", lastException.get());
             }
-            return true;
-        });
-        if (!success) {
-            throw new BindTransportException("Failed to bind to [" + port + "]", lastException.get());
+        } finally {
+            closeLock.writeLock().unlock();
         }
-
         if (logger.isDebugEnabled()) {
             logger.debug("Bound profile [{}] to address {{}}", name, NetworkAddress.format(boundSocket.get()));
         }
@@ -553,6 +553,7 @@ protected final void doClose() {
     protected final void doStop() {
         final CountDownLatch latch = new CountDownLatch(1);
         // make sure we run it on another thread than a possible IO handler thread
+        assert threadPool.generic().isShutdown() == false : "Must stop transport before terminating underlying threadpool";
         threadPool.generic().execute(() -> {
             closeLock.writeLock().lock();
             try {