server: keep most recent GetFieldRequester alive

src/server/pv/serverChannelImpl.h

@@ -47,6 +47,9 @@ public:
 
     void unregisterRequest(pvAccessID id);
 
+    void installGetField(const GetFieldRequester::shared_pointer& gf);
+    void completeGetField();
+
     //! may return NULL
     Destroyable::shared_pointer getRequest(pvAccessID id);
 
@@ -56,15 +59,15 @@ public:
 
     void printInfo(FILE *fd) const;
 private:
-    /**
-     * Local channel.
-     */
     const Channel::shared_pointer _channel;
 
     const ChannelRequester::shared_pointer _requester;
 
     const pvAccessID _cid, _sid;
 
+    //! keep alive in-progress GetField()
+    GetFieldRequester::shared_pointer _active_requester;
+
     typedef std::map<pvAccessID, Destroyable::shared_pointer> _requests_t;
     _requests_t _requests;
 

src/server/responseHandlers.cpp

@@ -2754,20 +2754,24 @@ void ServerGetFieldHandler::handleResponse(osiSockAddr* responseFrom,
     string subField = SerializeHelper::deserializeString(payloadBuffer, transport.get());
 
     // issue request
-    // TODO use std::make_shared
-    std::tr1::shared_ptr<ServerGetFieldRequesterImpl> tp(new ServerGetFieldRequesterImpl(_context, channel, ioid, transport));
-    GetFieldRequester::shared_pointer gfr = tp;
+    GetFieldRequester::shared_pointer req;
+    {
+        std::tr1::shared_ptr<ServerGetFieldRequesterImpl> tp(new ServerGetFieldRequesterImpl(_context, channel, ioid, transport));
+        req = tp;
+    }
 
     // asCheck
     Status asStatus = channel->getChannelSecuritySession()->authorizeGetField(ioid, subField);
     if (!asStatus.isSuccess())
     {
-        gfr->getDone(asStatus, FieldConstPtr());
+        req->getDone(asStatus, FieldConstPtr());
         return;
     }
 
+    channel->installGetField(req);
+
     // TODO exception check
-    channel->getChannel()->getField(gfr, subField);
+    channel->getChannel()->getField(req, subField);
 }
 
 void ServerGetFieldHandler::getFieldFailureResponse(Transport::shared_pointer const & transport, const pvAccessID ioid, const Status& errorStatus)
@@ -2792,6 +2796,7 @@ void ServerGetFieldRequesterImpl::getDone(const Status& status, FieldConstPtr co
     }
     TransportSender::shared_pointer thisSender = shared_from_this();
     _transport->enqueueSendRequest(thisSender);
+    _channel->completeGetField();
 }
 
 void ServerGetFieldRequesterImpl::destroy()

src/server/serverChannelImpl.cpp

@@ -108,5 +108,27 @@ void ServerChannel::printInfo(FILE *fd) const
     fprintf(fd,"CHANNEL      : %s\n", typeid(*_channel).name());
 }
 
+void ServerChannel::installGetField(const GetFieldRequester::shared_pointer& gf)
+{
+    GetFieldRequester::shared_pointer prev;
+    {
+        epicsGuard<epicsMutex> G(_mutex);
+        prev.swap(_active_requester);
+        _active_requester = gf;
+    }
+    if(prev) {
+        prev->getDone(Status::error("Aborted"), FieldConstPtr());
+    }
+}
+
+void ServerChannel::completeGetField()
+{
+    GetFieldRequester::shared_pointer prev;
+    {
+        epicsGuard<epicsMutex> G(_mutex);
+        prev.swap(_active_requester);
+    }
+}
+
 }
 }