Prevent multiple wakeup events on loop overrun

src/cactus_rt/cyclic_thread.cc

@@ -37,29 +37,42 @@ void CyclicThread::Run() noexcept {
     loop_latency = loop_end - loop_start;
     TrackLatency(wakeup_latency, loop_latency);
 
-    if (tracer_config.trace_overrun && static_cast<uint64_t>(wakeup_latency + loop_latency) >= period_ns_) {
-      Tracer().InstantEvent("LoopOverrun", "cactusrt");
-
-      LOG_WARNING_LIMIT(
-        std::chrono::milliseconds(100),
-        this->Logger(),
-        "At least 1 loop overrun detected in the last 100ms: latency ({}ns) > period ({}ns)",
-        loop_latency,
-        period_ns_
-      );
+    if (static_cast<uint64_t>(wakeup_latency + loop_latency) >= period_ns_) {
+      if (tracer_config.trace_overrun) {
+        Tracer().InstantEvent("LoopOverrun", "cactusrt", loop_end);
+
+        LOG_WARNING_LIMIT(
+          std::chrono::milliseconds(100),
+          this->Logger(),
+          "At least 1 loop overrun detected in the last 100ms: wakeup latency ({}ns) + loop latency ({}ns) > period ({}ns)",
+          wakeup_latency,
+          loop_latency,
+          period_ns_
+        );
+      }
+      // Loop has overrun - reset next wakeup time to now to ensure only one wakeup latency trace event is emitted
+      clock_gettime(CLOCK_MONOTONIC, &next_wakeup_time_);
+      next_wakeup_time_ns = next_wakeup_time_.tv_sec * 1'000'000'000 + next_wakeup_time_.tv_nsec;
+    } else {
+      next_wakeup_time_ = AddTimespecByNs(next_wakeup_time_, static_cast<int64_t>(period_ns_));
+      next_wakeup_time_ns = next_wakeup_time_.tv_sec * 1'000'000'000 + next_wakeup_time_.tv_nsec;
     }
 
     if (should_stop) {
       break;
     }
 
-    next_wakeup_time_ = AddTimespecByNs(next_wakeup_time_, static_cast<int64_t>(period_ns_));
-    next_wakeup_time_ns = next_wakeup_time_.tv_sec * 1'000'000'000 + next_wakeup_time_.tv_nsec;
+    if (tracer_config.trace_sleep) {
+      Tracer().StartSpan("Sleep", "cactusrt", loop_end);
+    }
+
+    // TODO: maybe track busy wait latency? That feature is not even enabled.
+    this->Config().scheduler->Sleep(next_wakeup_time_);
 
-    {
-      auto span = Tracer().WithSpan("Sleep", "cactusrt", tracer_config.trace_sleep);
-      // TODO: maybe track busy wait latency? That feature is not even enabled.
-      this->Config().scheduler->Sleep(next_wakeup_time_);
+    if (tracer_config.trace_sleep) {
+      // Ideally this should be next iteration's loop_start, but that may cause readability and runtime performance challenges
+      // Thus, the end of the sleep event may be after the end of the wakeup event by a small amount
+      Tracer().EndSpan(NowNs());
     }
   }
 }