From dcc8bfcd10d19176ee9d06dbd6cea1c1383e7e74 Mon Sep 17 00:00:00 2001
From: Simone Bordet <simone.bordet@gmail.com>
Date: Sat, 2 Aug 2014 00:01:56 +0200
Subject: [PATCH] Fixed a reentrancy issue that caused a stack overflow.

The case was that shutdown was called, ShutdownFlusherEntry called
flusher.close(), which called super.close(), which called
onCompleteFailure(), which looped over the active items to fail them,
calling again ShutdownFlusherEntry, which called again flusher.close(),
etc.
---
 .../org/eclipse/jetty/http2/HTTP2Session.java | 34 ++++++++++++++-----
 1 file changed, 26 insertions(+), 8 deletions(-)

diff --git a/jetty-http2/http2-common/src/main/java/org/eclipse/jetty/http2/HTTP2Session.java b/jetty-http2/http2-common/src/main/java/org/eclipse/jetty/http2/HTTP2Session.java
index 0b98d5c2b7d..dfdc4adc20f 100644
--- a/jetty-http2/http2-common/src/main/java/org/eclipse/jetty/http2/HTTP2Session.java
+++ b/jetty-http2/http2-common/src/main/java/org/eclipse/jetty/http2/HTTP2Session.java
@@ -588,11 +588,13 @@ public abstract class HTTP2Session implements ISession, Parser.Listener
         private final ByteBufferPool.Lease lease = new ByteBufferPool.Lease(generator.getByteBufferPool());
         private final int maxGather;
         private final List<FlusherEntry> active;
+        private final Queue<FlusherEntry> complete;
 
         private Flusher(int maxGather)
         {
             this.maxGather = maxGather;
             this.active = new ArrayList<>(maxGather);
+            this.complete = new ArrayDeque<>(maxGather);
         }
 
         private void append(FlusherEntry entry)
@@ -731,12 +733,19 @@ public abstract class HTTP2Session implements ISession, Parser.Listener
         public void succeeded()
         {
             lease.recycle();
+
+            // Transfer active items to avoid reentrancy.
             for (int i = 0; i < active.size(); ++i)
+                complete.add(active.get(i));
+            active.clear();
+
+            // Drain the queue one by one to avoid reentrancy.
+            while (!complete.isEmpty())
             {
-                FlusherEntry entry = active.get(i);
+                FlusherEntry entry = complete.poll();
                 entry.succeeded();
             }
-            active.clear();
+
             super.succeeded();
         }
 
@@ -749,31 +758,40 @@ public abstract class HTTP2Session implements ISession, Parser.Listener
         @Override
         protected void onCompleteFailure(Throwable x)
         {
-            LOG.debug(x);
+            if (LOG.isDebugEnabled())
+                LOG.debug(x);
+
             lease.recycle();
+
+            // Transfer active items to avoid reentrancy.
             for (int i = 0; i < active.size(); ++i)
+                complete.add(active.get(i));
+            active.clear();
+
+            // Drain the queue one by one to avoid reentrancy.
+            while (!complete.isEmpty())
             {
-                FlusherEntry entry = active.get(i);
+                FlusherEntry entry = complete.poll();
                 entry.failed(x);
             }
-            active.clear();
         }
 
         public void close()
         {
+            super.close();
+
             Queue<FlusherEntry> queued;
             synchronized (queue)
             {
-                super.close();
                 queued = new ArrayDeque<>(queue);
+                queue.clear();
             }        
 
             if (LOG.isDebugEnabled())
                 LOG.debug("Closing, queued={}", queued.size());
             
-            for (FlusherEntry item: queued)
+            for (FlusherEntry item : queued)
                 closed(item);
-
         }
 
         protected void closed(FlusherEntry item)