From 6fcfd60bd50092e2263dd00c1cb1cbce68c0f7fd Mon Sep 17 00:00:00 2001
From: Michael Davidsaver <mdavidsaver@gmail.com>
Date: Fri, 2 Jun 2017 12:32:12 +0200
Subject: [PATCH] BlockingUDPTransport wrap close() to break ref. loop

---
 src/remote/blockingUDPConnector.cpp | 21 ++++++++++++++++++++-
 src/remote/pv/blockingUDP.h         |  5 +++++
 src/server/serverContext.cpp        |  1 +
 3 files changed, 26 insertions(+), 1 deletion(-)

diff --git a/src/remote/blockingUDPConnector.cpp b/src/remote/blockingUDPConnector.cpp
index 44a447c..818c082 100644
--- a/src/remote/blockingUDPConnector.cpp
+++ b/src/remote/blockingUDPConnector.cpp
@@ -16,6 +16,22 @@
 using namespace std;
 using namespace epics::pvData;
 
+namespace {
+struct closer {
+    epics::pvAccess::Transport::shared_pointer P;
+    closer(const epics::pvAccess::Transport::shared_pointer& P) :P(P) {}
+    void operator()(epics::pvAccess::Transport*) {
+        try{
+            P->close();
+        }catch(...){
+            P.reset();
+            throw;
+        }
+        P.reset();
+    }
+};
+}
+
 namespace epics {
 namespace pvAccess {
 
@@ -72,7 +88,10 @@ Transport::shared_pointer BlockingUDPConnector::connect(TransportClient::shared_
     BlockingUDPTransport::shared_pointer transport(new BlockingUDPTransport(_serverFlag, responseHandler,
             socket, bindAddress, transportRevision));
 
-    return Transport::shared_pointer(transport);
+    // the worker thread holds a strong ref, which is released by transport->close()
+    Transport::shared_pointer ret(transport.get(), closer(transport));
+
+    return ret;
 }
 
 }
diff --git a/src/remote/pv/blockingUDP.h b/src/remote/pv/blockingUDP.h
index ba3d79a..dbbd310 100644
--- a/src/remote/pv/blockingUDP.h
+++ b/src/remote/pv/blockingUDP.h
@@ -35,6 +35,8 @@
 namespace epics {
 namespace pvAccess {
 
+class BlockingUDPConnector;
+
 enum InetAddressType { inetAddressType_all, inetAddressType_unicast, inetAddressType_broadcast_multicast };
 
 class BlockingUDPTransport : public epics::pvData::NoDefaultMethods,
@@ -46,10 +48,13 @@ class BlockingUDPTransport : public epics::pvData::NoDefaultMethods,
 public:
     POINTER_DEFINITIONS(BlockingUDPTransport);
 
+private:
+    friend class BlockingUDPConnector;
     BlockingUDPTransport(bool serverFlag,
                          ResponseHandler::shared_pointer const & responseHandler,
                          SOCKET channel, osiSockAddr &bindAddress,
                          short remoteTransportRevision);
+public:
 
     static shared_pointer create(bool serverFlag,
                                  ResponseHandler::shared_pointer const & responseHandler,
diff --git a/src/server/serverContext.cpp b/src/server/serverContext.cpp
index 5c49cd3..9b128ce 100644
--- a/src/server/serverContext.cpp
+++ b/src/server/serverContext.cpp
@@ -263,6 +263,7 @@ void ServerContextImpl::initialize()
     _timer.reset(new Timer("pvAccess-server timer", lowerPriority));
 
     ServerContextImpl::shared_pointer thisServerContext = shared_from_this();
+    // we create reference cycles here which are broken by our shutdown() method,
     _responseHandler.reset(new ServerResponseHandler(thisServerContext));
 
     _acceptor.reset(new BlockingTCPAcceptor(thisServerContext, _responseHandler, _ifaceAddr, _receiveBufferSize));