Scheduler won’t call tasks while using semaphores

I am having an issue with a project where the scheduler wont call tasks or the tasks are always in blocking state. Below is code and information. I am trying to learn RTOS and can’t figure out the issue. I am using FreeRTOS 10.1. Also if I remove all of the semaphore code the project works as desired and all the LED blink of and on. It only fails with the semaphore code added. This project is being used on a STM32F407 Discovery board. main.c ~~~

include “stm32f4xx_hal.h” // Keil::Device:STM32Cube HAL:Common

include “FreeRTOS.h” // ARM.FreeRTOS::RTOS:Core

include “task.h” // FreeRTOS task header

include “leds.h” // LED control header file

include “semphr.h” // ARM.FreeRTOS::RTOS:Core

xSemaphoreHandle gatekeeper = 0; void vGreenLedControlTask(void *pvParameters); void vRedLedControlTask(void *pvParameters); void vBlueLedControlTask(void *pvParameters); void vOrangeLedControlTask(void *pvParameters); int main() { printf(“starting Main(0)n”); printf(“initialize Ledsn”); LEDs_Init(); printf(“Creante Queue Handlen”); gatekeeper = xSemaphoreCreateMutex(); printf(“Creating Tasksn”);
                        "Blue LED Controller",

                        "Red LED Controller",
xTaskCreate(vOrangeLedControlTask, “Orange LED Controller”, 1024, NULL, 3, NULL); xTaskCreate(vGreenLedControlTask, “Green LED Controller”, 1024, NULL, 4, NULL); printf(“Starting Task Schedulern”);
vTaskStartScheduler(); printf(“Task Scheduler startedn”); while(1){} } void vGreenLedControlTask(void *pvParameters) { printf(“Entering Greenn”); while(1) { if(xSemaphoreTake(gatekeeper, 2500)) { GREEN_toggle(); xSemaphoreGive(gatekeeper); vTaskDelay(500); } else{ printf(“Green did not get the semaphoren”); } } } void vBlueLedControlTask(void *pvParameters) { printf(“Entering Bluen”); while(1) { if(xSemaphoreTake(gatekeeper, 2500)) { BLUE_toggle(); xSemaphoreGive(gatekeeper); vTaskDelay(2000); } else{ printf(“Blue did not receive semaphoren”); } } } void vRedLedControlTask(void *pvParameters) { while(1) { printf(“Entering Redn”); if(xSemaphoreTake(gatekeeper, 2500)) { RED_toggle(); xSemaphoreGive(gatekeeper); vTaskDelay(1500); } else{ printf(“Red did not get the semaphoren”);
} } } void vOrangeLedControlTask(void *pvParameters) { printf(“Entering Orangen”); while(1) { if(xSemaphoreTake(gatekeeper, 2500)) { ORANGE_toggle(); xSemaphoreGive(gatekeeper); vTaskDelay(1000); } else{ printf(“Orange did not get the semaphoren”); } } } ~~~ FreeRTOSConfig.h ~~~



/———————————————————– * Application specific definitions. * * These definitions should be adjusted for your particular hardware and * application requirements. * * THESE PARAMETERS ARE DESCRIBED WITHIN THE ‘CONFIGURATION’ SECTION OF THE * FreeRTOS API DOCUMENTATION AVAILABLE ON THE WEB SITE. * * See *———————————————————-/

include <stdint.h>

extern uint32_t SystemCoreClock;

define configCPUCLOCKHZ (SystemCoreClock)

define configTICKRATEHZ ((TickType_t)1000)

define configTOTALHEAPSIZE ((size_t)(4096))

define configMINIMALSTACKSIZE ((unsigned short)130)


define configMAX_PRIORITIES (5)

define configUSE_PREEMPTION 1

define configIDLESHOULDYIELD 1

define configMAXTASKNAME_LEN (10)

/* Software timer definitions. */

define configUSE_TIMERS 1

define configTIMERTASKPRIORITY (2)



define configUSE_MUTEXES 1



define configUSEQUEUESETS 1

define configUSEIDLEHOOK 0

define configUSETICKHOOK 0


define configUSE16BIT_TICKS 0

/* Set the following definitions to 1 to include the API function, or zero to exclude the API function. */

define INCLUDE_vTaskPrioritySet 1

define INCLUDE_uxTaskPriorityGet 1

define INCLUDE_vTaskDelete 1

define INCLUDE_vTaskSuspend 1

define INCLUDE_vTaskDelayUntil 1

define INCLUDE_vTaskDelay 1

define INCLUDE_eTaskGetState 1

/* Cortex-M specific definitions. */


/* __BVICPRIOBITS will be specified when CMSIS is being used. */ #define configPRIO_BITS __NVIC_PRIO_BITS


/* 15 priority levels */ #define configPRIO_BITS 4


/* The lowest interrupt priority that can be used in a call to a “set priority” function. */


/* The highest interrupt priority that can be used by any interrupt service routine that makes calls to interrupt safe FreeRTOS API functions. DO NOT CALL INTERRUPT SAFE FREERTOS API FUNCTIONS FROM ANY INTERRUPT THAT HAS A HIGHER PRIORITY THAN THIS! (higher priorities are lower numeric values. */


/* Interrupt priorities used by the kernel port layer itself. These are generic to all Cortex-M ports, and do not rely on any particular library functions. */


/* !!!! configMAXSYSCALLINTERRUPT_PRIORITY must not be set to zero !!!! See */


/* Normal assert() semantics without relying on the provision of an assert.h header file. */

define configASSERT( x ) if( ( x ) == 0 ) { taskDISABLE_INTERRUPTS(); for( ;; ); }

/* Map the FreeRTOS port interrupt handlers to their CMSIS standard names. */

define xPortPendSVHandler PendSV_Handler

define vPortSVCHandler SVC_Handler

define xPortSysTickHandler SysTick_Handler

/* Include debug event definitions */

include “freertos_evr.h”


~~~ Using Keil 5.25 the printf Debug viewer shows that the scheduler is started but no tasks ever execute. from debug window: starting Main() initialize Leds Create Semaphore Handle Creating Tasks Starting Task Scheduler Please let me know what I am doing wrong.

Scheduler won’t call tasks while using semaphores

Nothing is obviously wrong. If you pause the debugger, what is being executed (idle task? something else like a default interrupt handler that is just sitting in a loopo?). If you cut down the code so only one task is created at (configMAX_PRIORITIES – 1) priority, and put a break point on the first line of the task, is the break point ever hit – if not I suspect you just haven’t installed the necessary interrupt handlers as the scheduler is started with an SVC instruction. You can try stepping through the vTaskStartScheduler() function in the debugger to see how far it gets.

Scheduler won’t call tasks while using semaphores

If I pause and then start stepping into the code it keeps looping through the for(;;) loop of portTASKFUNCTION. It keeps calling prvCheckTasksWaitingTermination() function. It then goes to a while loop while(uxDeleteTasksWaitingCleanup > ( UBaseTypet) 0U). It never goes into this while loop because taskswaitingcleanup is always 0. It then goes to this if statement if( listCURRENTLISTLENGTH( &( pxReadyTasksLists[ tskIDLEPRIORITY ] ) ) > ( UBaseTypet ) 1 ) and then back to the prvCheckTasksWaitingTermination(). It does not enter the if statement. I will try the other steps you suggested next.

Scheduler won’t call tasks while using semaphores

This code is the expected behaviour of the idle task – which is the task created by the kernel itself and runs when there are no other application tasks to run.

Scheduler won’t call tasks while using semaphores

I ran the code with only one task as you described above. The single task never gets executed. I also was watching the NVIC register and none of the interrupts fired in the NVIC. What suggestion would you have next to track down this issue?

Scheduler won’t call tasks while using semaphores

Place a break point in prvPortStartFirstTask() within FreeRTOS/Source/portable/GCC/ARM_CM4F/port.c. (assuming GCC, otherwise the equivalent function for whichever compiler you are using). When the break point is hit, set the debugger to single step assembly instructions rather than C code, and step through the code until you execute the “svc 0” instruction – what happens then? The MCU should start executing an SVC handler, and I suspect it is just executing the wrong one.

Scheduler won’t call tasks while using semaphores

I will do as you suggested but just a quick update I was incorrect in my last statement. The NVIC has a 1 for the following interrupts NMI, Hard Fault, SVCALL, PENDSV, and SYSTICK. As I am new to ARM I am having trouble in tracing down exactly what is causing the issue. I will try your suggestion and post the results. Thanks for your help so far!

Scheduler won’t call tasks while using semaphores

I found out what the issue was. I had to increase the configTOTALHEAPSIZE size in the freeRTOSConfig.h file from 4096 to 15360. There was a fine line if I was 2048 less than 15360 it did not work and if I went 1024 above 15360 it would not work.