server: op->error() dispatch

Avoid blocking in error()

src/pvxs/source.h

@@ -30,6 +30,7 @@ public:
     //! @throws std::runtime_error if the client pvRequest() field mask does not select any fields of prototype.
     virtual void connect(const Value& prototype) =0;
     //! Indicate that this operation can not be setup
+    //! @since UNRELEASED Does not block
     virtual void error(const std::string& msg) =0;
 
     ConnectOp(const std::string& name,
@@ -145,6 +146,7 @@ public:
     virtual std::unique_ptr<MonitorControlOp> connect(const Value& prototype) =0;
 
     //! Indicate that this operation can not be setup
+    //! @since UNRELEASED Does not block
     virtual void error(const std::string& msg) =0;
 
     MonitorSetupOp(const std::string& name,

src/pvxs/srvcommon.h

@@ -94,6 +94,7 @@ struct PVXS_API ExecOp : public OpBase {
     //! Issue a reply with data.  For a GET or RPC  (or PUT/Get)
     virtual void reply(const Value& val) =0;
     //! Indicate the request has resulted in an error.
+    //! @since UNRELEASED Does not block
     virtual void error(const std::string& msg) =0;
 
     //! Callback invoked if the peer cancels the operation before reply() or error() is called.

src/serverget.cpp

@@ -203,7 +203,8 @@ struct ServerGPRConnect : public server::ConnectOp
         auto serv = server.lock();
         if(!serv)
             return;
-        serv->acceptor_loop.call([this, &msg](){
+        auto op(this->op);
+        serv->acceptor_loop.dispatch([op, msg](){
             if(auto oper = op.lock()) {
                 if(oper->state==ServerOp::Creating)
                     oper->doReply(Value(), msg);
@@ -273,7 +274,8 @@ struct ServerGPRExec : public server::ExecOp
         auto serv = server.lock();
         if(!serv)
             return;
-        serv->acceptor_loop.call([this, &val](){
+        auto op(this->op);
+        serv->acceptor_loop.dispatch([op, val](){
             if(auto oper = op.lock()) {
                 oper->doReply(val, std::string());
             }
@@ -287,7 +289,8 @@ struct ServerGPRExec : public server::ExecOp
         auto serv = server.lock();
         if(!serv)
             return;
-        serv->acceptor_loop.call([this, &msg](){
+        auto op(this->op);
+        serv->acceptor_loop.dispatch([op, msg](){
             if(auto oper = op.lock()) {
                 oper->doReply(Value(), msg);
             }

src/servermon.cpp

@@ -399,10 +399,11 @@ struct ServerMonitorSetup : public server::MonitorSetupOp
         auto serv = server.lock();
         if(!serv)
             return;
-        serv->acceptor_loop.call([this, &msg](){
+        auto op(this->op);
+        serv->acceptor_loop.dispatch([op, msg]() mutable {
             if(auto oper = op.lock()) {
                 if(oper->state==ServerOp::Creating) {
-                    oper->msg = msg;
+                    oper->msg = std::move(msg);
                     oper->doReply();
                 }
             }