replace atomics with stop events in periodic metrics

Author: Pavel Harbanau

apps/services/app_execution_metrics/executor_metrics_manager.h

@@ -52,26 +52,20 @@ class app_executor_metrics_service
     {
       metrics_exec = &metrics_exec_;
 
-      if (stopped.exchange(false, std::memory_order_relaxed)) {
-        sync_event wait_all;
-
-        defer_until_success(*metrics_exec, timers, [this, token = wait_all.get_token()]() mutable {
-          // Start the executor metrics backend.
-          exec_metrics_backend.start(report_period, timers.create_unique_timer(*metrics_exec), notifier);
-        });
-        wait_all.wait();
-      }
+      sync_event wait_all;
+
+      defer_until_success(*metrics_exec, timers, [this, token = wait_all.get_token()]() mutable {
+        // Start the executor metrics backend.
+        exec_metrics_backend.start(report_period, timers.create_unique_timer(*metrics_exec), notifier);
+      });
+      wait_all.wait();
     }
 
     /// Stops the metrics backend.
     void stop()
     {
-      if (not stopped.exchange(true, std::memory_order_relaxed)) {
-        sync_event wait_all;
-        defer_until_success(
-            *metrics_exec, timers, [this, token = wait_all.get_token()]() mutable { exec_metrics_backend.stop(); });
-        wait_all.wait();
-      }
+      // Blocking call.
+      exec_metrics_backend.stop();
     }
 
     /// Application timers manager.
@@ -84,8 +78,6 @@ class app_executor_metrics_service
     executor_metrics_backend exec_metrics_backend;
     /// Notifier used by the backend to notify metrics.
     executor_metrics_notifier& notifier;
-    /// Operation status of this service.
-    std::atomic<bool> stopped{true};
   };
 
   /// Callback called on session destruction.

apps/services/metrics/periodic_metrics_report_controller.h

@@ -45,15 +45,12 @@ class periodic_metrics_report_controller
     if (!report_period.count()) {
       return;
     }
-    if (stopped.exchange(false, std::memory_order_relaxed)) {
-      std::promise<void> exit_signal;
-      auto               fut = exit_signal.get_future();
-      defer_until_success(executor, timers, [this, &exit_signal]() mutable {
-        timer.run();
-        exit_signal.set_value();
-      });
-      fut.wait();
-    }
+    stop_manager.reset();
+
+    sync_event wait_all;
+    defer_until_success(executor, timers, [this, token = wait_all.get_token()]() mutable { timer.run(); });
+    // Block waiting for the controller to start.
+    wait_all.wait();
   }
 
   /// Stops the metrics report timer.
@@ -62,20 +59,23 @@ class periodic_metrics_report_controller
     if (!report_period.count()) {
       return;
     }
-    if (not stopped.exchange(true, std::memory_order_relaxed)) {
-      sync_event wait_all;
-      defer_until_success(executor, timers, [this, token = wait_all.get_token()]() mutable { timer.stop(); });
-      wait_all.wait();
-    }
+
+    // Signal stop to asynchronous timer thread.
+    stop_manager.stop();
+    // Stop the timer.
+    timer.stop();
   }
 
 private:
   /// Trigger metrics report in all registered producers.
   void report_metrics()
   {
-    if (stopped.load(std::memory_order_relaxed)) {
+    auto token = stop_manager.get_token();
+    // Do not rearm the timer and process metrics if stop was requested.
+    if (SRSRAN_UNLIKELY(token.is_stop_requested())) {
       return;
     }
+
     // Rearm the timer.
     timer.run();
 
@@ -92,7 +92,8 @@ class periodic_metrics_report_controller
   unique_timer timer;
   /// Metrics report period.
   std::chrono::milliseconds report_period{0};
-  std::atomic<bool>         stopped{true};
+  /// Manager used for stopping this controller.
+  stop_event_source stop_manager;
   /// List of metrics producers managed by this controller.
   std::vector<metrics_producer*> producers;
 };

include/srsran/support/executors/metrics/executor_metrics_backend.h

@@ -43,7 +43,7 @@ class executor_metrics_backend : public executor_metrics_channel_registry
   // See interface for documentation.
   executor_metrics_channel& add_channel(const std::string& exec_name) override;
 
-  /// Stops periodic metrics reporting.
+  /// Stops periodic metrics reporting. This method is blocking.
   void stop();
 
   /// Start the backend worker using the passed timer and periodically report metrics to the given notifier object.

lib/support/executors/metrics/executor_metrics_backend.cpp

@@ -39,6 +39,7 @@ void executor_metrics_backend::stop()
 {
   // Signal stop to asynchronous timer thread.
   stop_control.stop();
+  // Stop the timer.
   timer.stop();
 
   notifier = nullptr;