use the volatile global enabled flag

protocol/esta/sacn/universesender.cpp

@@ -43,7 +43,7 @@ UniverseSender::UniverseSender(Source * source, Universe * universe)
     , minimum_update_time(22700)
     , retransmission_count(0)
     , keep_alive_interval(800)
-    , enable_(true)
+    , enabled_(true)
     , last_data_({0})
     , dmp_(std::make_shared<ACN::DMP::Pdu>())
     , frame_(std::make_shared<DATA::Pdu>())
@@ -115,7 +115,7 @@ void UniverseSender::kill()
 {
   {
     std::unique_lock lk_ctl(mtx_control);
-    enable_ = false;
+    enabled_ = false;
   }
   flush();
 }
@@ -126,7 +126,6 @@ void UniverseSender::kill()
  */
 void UniverseSender::loop_()
 {
-  bool enabled = true; // at least 1 loop
   bool new_data;
   std::chrono::nanoseconds elapsed;
   std::chrono::microseconds sleep;
@@ -134,20 +133,14 @@ void UniverseSender::loop_()
 
   update_dmp_(); // initial data segment
 
-  while (enabled || terminated_resend > 0)
+  while (enabled_ || terminated_resend > 0)
     {
       // enforce strict minimum update times
       elapsed = std::chrono::system_clock::now() - mUniverse->last_updated_;
       if (elapsed < minimum_update_time)
         std::this_thread::sleep_for(minimum_update_time - elapsed);
 
-      // check for control permission to continue looping
-      {
-          std::shared_lock lk_ctl(mtx_control);
-          enabled = enable_;
-      }
-
-      if (enable_)
+      if (enabled_)
         {
           mUniverse->setStatus(Universe::DMX_ACTIVE);
           std::shared_lock lk_data(mUniverse->mtx_data);

protocol/esta/sacn/universesender.h

@@ -81,7 +81,7 @@ private:
     /// > intervals of between 800mS and 1000mS.
     const std::chrono::milliseconds keep_alive_interval;
 
-    bool enable_;
+    volatile bool enabled_;
     mutable std::shared_mutex mtx_control;
     mutable std::mutex mtx_thread_;
     std::condition_variable_any request_;