FreeRTOS Task should not return - ESP32

Question

I'm using multi-threading on my ESP32. I have created two tasks and pinned them to core 1. With one of them, I get the following error:

E (20426) FreeRTOS: FreeRTOS Task "MeasurementTask" should not return, Aborting now!
abort() was called at PC 0x4008b8f3 on core 1

Backtrace: 0x4008f34c:0x3ffd0a40 0x4008f57d:0x3ffd0a60 0x4008b8f3:0x3ffd0a80

Rebooting...

However, there is no return statement in my "MeasurementTask" (see code below). What's the issue here?

tracker.cpp:

#include "tracker.h"

void threadedLoop(void *pvParameters) {
  Serial.println("Loop task pinned");
  for(;;) {
    checkAPTrigger();
    mqttLoop();
  }
}

void setupTracker() {
  Serial.print("Setup start: ");
  Serial.println(millis());
  Wire.begin();
  setup_sensors();
  if(setupAP()) {
    setupTime();
    setupMQTT();
  }
  Serial.print("Setup done: ");
  Serial.println(millis());

  Serial.println("Pinning measurement");
  TaskHandle_t measureTask;
  xTaskCreatePinnedToCore(
    takeMeasurement,
    "MeasurementTask",
    2048,
    NULL,
    1,
    NULL,
    ARDUINO_RUNNING_CORE
  );

  Serial.println("Pinning loop");
  TaskHandle_t loopTask;
  xTaskCreatePinnedToCore(
    threadedLoop,
    "LoopTask",
    2048,
    NULL,
    1,
    NULL,
    ARDUINO_RUNNING_CORE
  );
}

void loopTracker() {
  //takeMeasurement();
}

void takeMeasurement(void *pvParameters) {
  Serial.println("Measurement task pinned");
  DynamicJsonDocument root(512);
  JsonObject rootObj = root.to<JsonObject>();
  read_sensors(rootObj);

  if(!(settings.mqttUsed && publishData(rootObj))) {
    appendFile("data", root);
  }

  serializeJsonPretty(root, Serial);
  Serial.println("\n---\n");
}

Sketch:

#include <tracker.h>

void setup() {
  Serial.begin(115200);
  // put your setup code here, to run once:
  wm.resetSettings();
  setupTracker();
}

void loop() {
  // put your main code here, to run repeatedly:
  loopTracker();
}

There are quite some files included in the tracker.h, but I don't believe they're relevant to this problem. Some of the functions used in the takeMeasurement do have return values, but I never return them in that function itself.

Answer 1

In FreeRTOS, tasks are started with xTaskCreate... and ended with vTaskDelete. A task function may not simply "end", this is not allowed.

Put vTaskDelete(NULL); at the end of the function to gracefully end the task:

void takeMeasurement(void *pvParameters) {
  // . . . task code . . .
  vTaskDelete(NULL);
}

Having said that, tasks are usually meant to be long-running. For example, the measurement task could be an endless loop that takes the measurement, sleeps for a while, and repeats.

Answer 2

It seems to me that You forgot to add an infinite loop:

void takeMeasurement(void *pvParameters) {
    for(;;){ // ** Start of infinite loop **
        Serial.println("Measurement task pinned");
        DynamicJsonDocument root(512);
        JsonObject rootObj = root.to<JsonObject>();
        read_sensors(rootObj);
    
        if(!(settings.mqttUsed && publishData(rootObj))) {
            appendFile("data", root);
        }
    
        serializeJsonPretty(root, Serial);
        Serial.println("\n---\n");
    }   // ** End of infinite loop **
}