I have 2 Tasks, both will give turns in printing a string (shared resource) on the serial monitor. I’m using a ESP-32 microcontroller and FreeRTOS, also the Arduino IDE.

I’m trying to use binary semaphores for mutual exclusion as practice (instead of mutexes)

Here is my work in an emulator:
https://wokwi.com/projects/403426133978368001

I implemented the binary semaphores, but for some reason I’m not achieving mutual exclusion.

Here’s my code:

// Choose the core, if this macro (found in sdkconfig of ESP-32 configuration system files) 
#if CONFIG_FREERTOS_UNICORE  //this will return false (reading from config in freertos.h file), so we’ll set it to run on the second core app_cpu=1
static const BaseType_t app_cpu = 0;
#else
static const BaseType_t app_cpu = 1;
#endif

// Global variables

// Message
char buffer[] = "Mary had a little lamb";

// Binary semaphore
SemaphoreHandle_t bin_sem;

// Task1
void Task1_Function(void *params)
{
    uint8_t i;
    uint8_t msg_len = strlen(buffer);
  
    while (1)
    {
        // Take the binary semaphore, value of bin_sem now 0
        xSemaphoreTake(bin_sem, portMAX_DELAY);
       
        /******* CRITICAL SECTION START *******/
        // Read (print) whatever is in the buffer
        Serial.print("Task1: ");
        for (i = 0; i < msg_len; i++)
        {
            Serial.print(buffer[i]);
        }
        Serial.println();
        /******* CRITICAL SECTION END *******/

        // Give the semaphore, value of bin_sem now back to 1
        xSemaphoreGive(bin_sem);

        vTaskDelay(pdMS_TO_TICKS(1000)); // Adjust the delay as necessary
    }
}

// Task2
void Task2_Function(void *params)
{
    uint8_t i;
    uint8_t msg_len = strlen(buffer);
  
    while (1)
    {
        // Take the binary semaphore, value of bin_sem now 0
        xSemaphoreTake(bin_sem, portMAX_DELAY);
       
        /******* CRITICAL SECTION START *******/
        // Read (print) whatever is in the buffer
        Serial.print("Task2: ");
        for (i = 0; i < msg_len; i++)
        {
            Serial.print(buffer[i]);
        }
        Serial.println();
        /******* CRITICAL SECTION END *******/
        
        // Give the semaphore, value of bin_sem now back to 1
        xSemaphoreGive(bin_sem);

        vTaskDelay(pdMS_TO_TICKS(1000)); // Adjust the delay as necessary
    }
}

void setup() 
{
    // Initialize Serial monitor
    Serial.begin(9600);

    BaseType_t status;
    TaskHandle_t task1_handler, task2_handler;

    // Create binary semaphore
    bin_sem = xSemaphoreCreateBinary(); // Note this is initialized to 0
    xSemaphoreGive(bin_sem);     // bin sem now 1, ready to be taken
    
    // Task 1 Creation 
    status = xTaskCreatePinnedToCore(Task1_Function,
                                     "Task-1-Function",
                                     1024,  // This is stack size in words, in bytes for a 32bit miccrocontroller each word is 4 bytes. so 1024*4 = 4096 bytes
                                     NULL,  // No parameters passed
                                     1,     // Priority
                                     &task1_handler,
                                     app_cpu
                                    );

    // Check if task creation, memory allocation was successful
    if (status != pdTRUE)
    {
        Serial.println("Error Task1 creation failed");     // Using Arduino IDE
    }
    // Or you can use the assert
    // configASSERT(status == pdTRUE);

    // Task 2 Creation 
    status = xTaskCreatePinnedToCore(Task2_Function,
                                     "Task-2-Function",
                                     1024,  // This is stack size in words, in bytes for a 32bit miccrocontroller each word is 4 bytes. so 1024*4 = 4096 bytes
                                     NULL,  // No parameters passed
                                     1,     // Priority
                                     &task2_handler,
                                     app_cpu
                                    );

    // Check if task creation, memory allocation was successful
    if (status != pdTRUE)
    {
        Serial.println("Error Task2 creation failed");     // Using Arduino IDE
    }
    // Or you can use the assert
    // configASSERT(status == pdTRUE);
}

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

The output:

mode:DIO, clock div:2
load:0x3fff0030,len:1156
load:0x40078000,len:11456
ho 0 tail 12 room 4
load:0x40080400,len:2972
entry 0x400805dc
Task1: Mary had a little lamb
Task2: Mary had a little lamb
Task1: Mary had a little lamb

The tasks execute fine at first but then they get stuck, there’s also sometimes where a message while printing gets interrupted.
I honestly don’t know why the code is wrong, so any help is greatly appreciated.