From f6f72c871cd93e7f2673efea1c9cf353acc3106e Mon Sep 17 00:00:00 2001
From: HarunTeper <harun.teper@tu-dortmund.de>
Date: Mon, 9 Dec 2024 14:35:06 +0100
Subject: [PATCH 1/2] Added test for starvation in the multi-threaded executor

Signed-off-by: HarunTeper <harun.teper@tu-dortmund.de>
---
 .../test_multi_threaded_executor.cpp          | 63 +++++++++++++++++++
 1 file changed, 63 insertions(+)

diff --git a/rclcpp/test/rclcpp/executors/test_multi_threaded_executor.cpp b/rclcpp/test/rclcpp/executors/test_multi_threaded_executor.cpp
index 09dfa03f90..32872482c4 100644
--- a/rclcpp/test/rclcpp/executors/test_multi_threaded_executor.cpp
+++ b/rclcpp/test/rclcpp/executors/test_multi_threaded_executor.cpp
@@ -102,3 +102,66 @@ TEST_F(TestMultiThreadedExecutor, timer_over_take) {
   executor.add_node(node);
   executor.spin();
 }
+
+/*
+   Test that no tasks are starved
+ */
+TEST_F(TestMultiThreadedExecutor, starvation) {
+  rclcpp::executors::MultiThreadedExecutor executor(rclcpp::ExecutorOptions(),
+                                                    2u);
+
+  std::shared_ptr<rclcpp::Node> node =
+      std::make_shared<rclcpp::Node>("test_multi_threaded_executor_starvation");
+
+  std::atomic_int timer_one_count{0};
+  std::atomic_int timer_two_count{0};
+
+  rclcpp::TimerBase::SharedPtr timer_one;
+  rclcpp::TimerBase::SharedPtr timer_two;
+
+  auto timer_one_callback = [&timer_one_count, &timer_two_count]() {
+    std::cout << "Timer one callback executed. Count: "
+              << timer_one_count.load() << std::endl;
+
+    auto start_time = std::chrono::steady_clock::now();
+    while (std::chrono::steady_clock::now() - start_time < 100ms) {
+    }
+
+    timer_one_count++;
+
+    auto diff = std::abs(timer_one_count - timer_two_count);
+
+    std::cout << "Difference in counts: " << diff << std::endl;
+
+    if (diff > 1) {
+      rclcpp::shutdown();
+      ASSERT_LE(diff, 1);
+    }
+  };
+
+  auto timer_two_callback = [&timer_one_count, &timer_two_count]() {
+    std::cout << "Timer two callback executed. Count: "
+              << timer_two_count.load() << std::endl;
+
+    auto start_time = std::chrono::steady_clock::now();
+    while (std::chrono::steady_clock::now() - start_time < 100ms) {
+    }
+
+    timer_two_count++;
+
+    auto diff = std::abs(timer_one_count - timer_two_count);
+
+    std::cout << "Difference in counts: " << diff << std::endl;
+
+    if (diff > 1) {
+      rclcpp::shutdown();
+      ASSERT_LE(diff, 1);
+    }
+  };
+
+  timer_one = node->create_wall_timer(0ms, timer_one_callback);
+  timer_two = node->create_wall_timer(0ms, timer_two_callback);
+
+  executor.add_node(node);
+  executor.spin();
+}

From af9b7c8f6a112f21cf1c6849231e7c4d75d65a95 Mon Sep 17 00:00:00 2001
From: HarunTeper <harun.teper@tu-dortmund.de>
Date: Mon, 6 Jan 2025 12:24:02 +0000
Subject: [PATCH 2/2] Refactor starvation test in multi-threaded executor to
 use sleep instead of busy wait

Signed-off-by: HarunTeper <harun.teper@tu-dortmund.de>
---
 .../test_multi_threaded_executor.cpp          | 24 +++++--------------
 1 file changed, 6 insertions(+), 18 deletions(-)

diff --git a/rclcpp/test/rclcpp/executors/test_multi_threaded_executor.cpp b/rclcpp/test/rclcpp/executors/test_multi_threaded_executor.cpp
index 32872482c4..59c9735458 100644
--- a/rclcpp/test/rclcpp/executors/test_multi_threaded_executor.cpp
+++ b/rclcpp/test/rclcpp/executors/test_multi_threaded_executor.cpp
@@ -120,12 +120,7 @@ TEST_F(TestMultiThreadedExecutor, starvation) {
   rclcpp::TimerBase::SharedPtr timer_two;
 
   auto timer_one_callback = [&timer_one_count, &timer_two_count]() {
-    std::cout << "Timer one callback executed. Count: "
-              << timer_one_count.load() << std::endl;
-
-    auto start_time = std::chrono::steady_clock::now();
-    while (std::chrono::steady_clock::now() - start_time < 100ms) {
-    }
+    std::this_thread::sleep_for(100ms);
 
     timer_one_count++;
 
@@ -133,34 +128,27 @@ TEST_F(TestMultiThreadedExecutor, starvation) {
 
     std::cout << "Difference in counts: " << diff << std::endl;
 
-    if (diff > 1) {
+    if (timer_one_count > 10 || timer_two_count > 10) {
       rclcpp::shutdown();
       ASSERT_LE(diff, 1);
     }
   };
 
   auto timer_two_callback = [&timer_one_count, &timer_two_count]() {
-    std::cout << "Timer two callback executed. Count: "
-              << timer_two_count.load() << std::endl;
-
-    auto start_time = std::chrono::steady_clock::now();
-    while (std::chrono::steady_clock::now() - start_time < 100ms) {
-    }
+    std::this_thread::sleep_for(100ms);
 
     timer_two_count++;
 
     auto diff = std::abs(timer_one_count - timer_two_count);
 
-    std::cout << "Difference in counts: " << diff << std::endl;
-
-    if (diff > 1) {
+    if (timer_one_count > 10 || timer_two_count > 10) {
       rclcpp::shutdown();
       ASSERT_LE(diff, 1);
     }
   };
 
-  timer_one = node->create_wall_timer(0ms, timer_one_callback);
-  timer_two = node->create_wall_timer(0ms, timer_two_callback);
+  timer_one = node->create_wall_timer(10ms, timer_one_callback);
+  timer_two = node->create_wall_timer(10ms, timer_two_callback);
 
   executor.add_node(node);
   executor.spin();