feat(task): Allow task thread to call stop(); add support for getting task thread id (#309)

* feat(task): Allow task thread to call stop(); add support for getting task thread id

* update to ensure task_handle_ is unset when joined

* fix printing of id on other platforms

* update how id is managed for cleaner / more maintainable code

* only use task_handle_ on esp

Author: finger563

Diff for: components/task/example/main/task_example.cpp

@@ -367,8 +367,9 @@ extern "C" void app_main(void) {
     task.start();
     auto stop_fn = [&task]() {
       std::this_thread::sleep_for(1s);
-      auto thread = xTaskGetCurrentTaskHandle();
-      fmt::print("Stopping task from thread {}...\n", fmt::ptr(thread));
+      // NOTE: on ESP-IDF, this is the same as xTaskGetCurrentTaskHandle();
+      auto thread = espp::Task::get_current_id();
+      fmt::print("Stopping task from thread {}...\n", thread);
       task.stop();
     };
     // make vector of threads to stop the task
@@ -387,6 +388,47 @@ extern "C" void app_main(void) {
     //! [Task Request Stop From Multiple Threads example]
   }
 
+  /**
+    * Show an example of a task which calls stop on itself from within the task
+    */
+  test_start = std::chrono::high_resolution_clock::now();
+  {
+    fmt::print("Task Request Stop From Within Task example\n");
+    //! [Task Request Stop From Within Task example]
+    espp::Task task = espp::Task({.name = "Self Stopping Task",
+                            .callback =
+          [&num_seconds_to_run, &task](std::mutex &m, std::condition_variable &cv) {
+            static auto begin = std::chrono::high_resolution_clock::now();
+            auto now = std::chrono::high_resolution_clock::now();
+            auto elapsed = std::chrono::duration<float>(now - begin).count();
+            fmt::print("Task has run for {:.03f} seconds\n", elapsed);
+            // NOTE: sleeping in this way allows the sleep to exit early when the
+            // task is being stopped / destroyed
+            {
+              std::unique_lock<std::mutex> lk(m);
+              cv.wait_for(lk, 100ms);
+            }
+            if (elapsed > num_seconds_to_run) {
+              fmt::print("Stopping task from within task...\n");
+              task.stop();
+            }
+            // do some other work here which can't be preempted, this helps force the
+            // stopping threads to try to contend on the thread join within the stop
+            // call
+            std::this_thread::sleep_for(50ms);
+            // we don't want to stop yet, so return false
+            return false;
+          },
+
+                            .log_level = espp::Logger::Verbosity::DEBUG});
+    task.start();
+    while (task.is_started()) {
+      std::this_thread::sleep_for(50ms);
+    }
+    fmt::print("Task successfully stopped by itself!\n");
+    //! [Task Request Stop From Within Task example]
+  }
+
   {
     //! [run on core example]
     fmt::print("Example main running on core {}\n", xPortGetCoreID());

Diff for: components/task/include/task.hpp

@@ -44,6 +44,12 @@ namespace espp {
  */
 class Task : public espp::BaseComponent {
 public:
+  #if defined(ESP_PLATFORM)
+  typedef void* task_id_t;
+  #else
+  typedef std::thread::id task_id_t;
+  #endif
+
   /**
    * @brief Task callback function signature.
    *
@@ -191,10 +197,12 @@ class Task : public espp::BaseComponent {
   bool start();
 
   /**
-   * @brief Stop the task execution, blocking until it stops.
-   *
+   * @brief Stop the task execution.
+   * @details This will request the task to stop, notify the condition variable,
+   *          and (if this calling context is not the task context) join the
+   *          thread.
    * @return true if the task stopped, false if it was not started / already
-   * stopped.
+   *         stopped.
    */
   bool stop();
 
@@ -231,6 +239,30 @@ class Task : public espp::BaseComponent {
   static std::string get_info(const Task &task);
 #endif
 
+  /**
+   * @brief Get the ID for this Task's thread / task context.
+   * @return ID for this Task's thread / task context.
+   */
+  task_id_t get_id() const {
+    #if defined(ESP_PLATFORM)
+    return task_handle_;
+    #else
+    return thread_.get_id();
+    #endif
+  }
+
+  /**
+   * @brief Get the ID for the current thread / task context.
+   * @return ID for the current thread / task context.
+   */
+  static task_id_t get_current_id() {
+    #if defined(ESP_PLATFORM)
+    return static_cast<task_id_t>(xTaskGetCurrentTaskHandle());
+    #else
+    return std::this_thread::get_id();
+    #endif
+  }
+
 protected:
   /**
    * @brief Function that is run in the task thread.
@@ -256,6 +288,9 @@ class Task : public espp::BaseComponent {
   std::mutex cv_m_;
   std::mutex thread_mutex_;
   std::thread thread_;
+  #if defined(ESP_PLATFORM)
+  task_id_t task_handle_;
+  #endif
 };
 } // namespace espp
 

Diff for: components/task/src/task.cpp

@@ -108,11 +108,16 @@ void Task::notify_and_join() {
     std::lock_guard<std::mutex> lock(cv_m_);
     cv_.notify_all();
   }
-  {
-    std::lock_guard<std::mutex> lock(thread_mutex_);
-    if (thread_.joinable()) {
-      thread_.join();
-    }
+  auto thread_id = get_id();
+  auto current_id = get_current_id();
+  logger_.debug("Thread id: {}, current id: {}", thread_id, current_id);
+  // check to ensure we're not the same thread
+  std::lock_guard<std::mutex> lock(thread_mutex_);
+  if (thread_.joinable() && current_id != thread_id) {
+    thread_.join();
+#if defined(ESP_PLATFORM)
+    task_handle_ = nullptr;
+#endif
   }
 }
 
@@ -127,14 +132,17 @@ std::string Task::get_info() {
 }
 
 std::string Task::get_info(const Task &task) {
-  TaskHandle_t freertos_handle = xTaskGetHandle(task.name_.c_str());
+  TaskHandle_t freertos_handle = static_cast<TaskHandle_t>(task.get_id());
   return fmt::format("[T] '{}',{},{},{}\n", pcTaskGetName(freertos_handle), xPortGetCoreID(),
                      uxTaskPriorityGet(freertos_handle),
                      uxTaskGetStackHighWaterMark(freertos_handle));
 }
 #endif
 
 void Task::thread_function() {
+#if defined(ESP_PLATFORM)
+  task_handle_ = get_current_id();
+#endif
   while (started_) {
     if (callback_) {
       bool should_stop = callback_(cv_m_, cv_);