Why are tasks not firing in FreeRTOS when using semaphores

[Paul Leslie]

I have a project that I am trying to do to learn using RTOS on STM32F407 Discovery board. I am trying to use semaphores on 4 tasks but after the scheduler starts none of the tasks are firing. Below is the code:

#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()\n");
	printf("initialize Leds\n");
	LEDs_Init();
	printf("Create Semaphore Handle\n");
	gatekeeper = xSemaphoreCreateMutex();
	printf("Creating Tasks\n");
	
	xTaskCreate(vBlueLedControlTask,
							"Blue LED Controller",
							1024,
							NULL,
							1,
							NULL);
	
	xTaskCreate(vRedLedControlTask,
							"Red LED Controller",
							1024,
							NULL,
							2,
							NULL);
 
 
xTaskCreate(vOrangeLedControlTask,
							"Orange LED Controller",
							1024,
							NULL,
							3,
							NULL);
 
xTaskCreate(vGreenLedControlTask,
							"Green LED Controller",
							1024,
							NULL,
							4,
							NULL);
			printf("Starting Task Scheduler\n");												
vTaskStartScheduler();
 
 
while(1){}
}
 
 
void vGreenLedControlTask(void *pvParameters)
{
	printf("Entering Green\n");
	while(1)
	{
		if(xSemaphoreTake(gatekeeper, 2500))
		{
			GREEN_toggle();
			xSemaphoreGive(gatekeeper);
			vTaskDelay(500);
		}
		else{
			printf("Green did not get the semaphore\n");
		}
	}
}
 
void vBlueLedControlTask(void *pvParameters)
{
	printf("Entering Blue\n");
	while(1)
	{
		if(xSemaphoreTake(gatekeeper, 2500))
		{
			BLUE_toggle();
			xSemaphoreGive(gatekeeper);
			vTaskDelay(2000);
		}
		else{
			printf("Blue did not receive semaphore\n");
		}
	}
}
 
void vRedLedControlTask(void *pvParameters)
{
	while(1)
	{
		printf("Entering Red\n");
		if(xSemaphoreTake(gatekeeper, 2500))
		{
			RED_toggle();
			xSemaphoreGive(gatekeeper);
			vTaskDelay(1500);
		}
		else{
		printf("Red did not get the semaphore\n");	
		}
	}
}
 
void vOrangeLedControlTask(void *pvParameters)
{
	printf("Entering Orange\n");
	while(1)
	{
		if(xSemaphoreTake(gatekeeper, 2500))
		{
			ORANGE_toggle();
			xSemaphoreGive(gatekeeper);
			vTaskDelay(1000);
		}
		else{
			printf("Orange did not get the semaphore\n");
		}
  }
}
 

FreeRTOSConfig.h file:

/*
 * FreeRTOS Kernel V10.0.1
 * Copyright (C) 2017 Amazon.com, Inc. or its affiliates.  All Rights Reserved.
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy of
 * this software and associated documentation files (the "Software"), to deal in
 * the Software without restriction, including without limitation the rights to
 * use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of
 * the Software, and to permit persons to whom the Software is furnished to do so,
 * subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in all
 * copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS
 * FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR
 * COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER
 * IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
 * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
 *
 * http://www.FreeRTOS.org
 * http://aws.amazon.com/freertos
 *
 * 1 tab == 4 spaces!
 */
 
 
#ifndef FREERTOS_CONFIG_H
#define FREERTOS_CONFIG_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 FreeRTOS.org WEB SITE.
 *
 * See http://www.freertos.org/a00110.html.
 *----------------------------------------------------------*/
 
#include <stdint.h>
 
extern uint32_t SystemCoreClock;
 
#define configCPU_CLOCK_HZ                    (SystemCoreClock)
#define configTICK_RATE_HZ                    ((TickType_t)1000)
#define configTOTAL_HEAP_SIZE                 ((size_t)(4096))
#define configMINIMAL_STACK_SIZE              ((unsigned short)130)
#define configCHECK_FOR_STACK_OVERFLOW        0
#define configMAX_PRIORITIES                  (5)
#define configUSE_PREEMPTION                  1
#define configIDLE_SHOULD_YIELD               1
#define configMAX_TASK_NAME_LEN               (10)
 
/* Software timer definitions. */
#define configUSE_TIMERS                      1
#define configTIMER_TASK_PRIORITY             (2)
#define configTIMER_QUEUE_LENGTH              5
#define configTIMER_TASK_STACK_DEPTH          (configMINIMAL_STACK_SIZE * 2)
 
#define configUSE_MUTEXES                     1
#define configUSE_RECURSIVE_MUTEXES           1
#define configUSE_COUNTING_SEMAPHORES         1
#define configUSE_QUEUE_SETS                  1
#define configUSE_IDLE_HOOK                   0
#define configUSE_TICK_HOOK                   0
#define configUSE_MALLOC_FAILED_HOOK          0
#define configUSE_16_BIT_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. */
#ifdef __NVIC_PRIO_BITS
  /* __BVIC_PRIO_BITS will be specified when CMSIS is being used. */
  #define configPRIO_BITS                     __NVIC_PRIO_BITS
#else
  /* 15 priority levels */
  #define configPRIO_BITS                     4
#endif
 
/* The lowest interrupt priority that can be used in a call to a "set priority"
function. */
#define configLIBRARY_LOWEST_INTERRUPT_PRIORITY       0xff
 
/* 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. */
#define configLIBRARY_MAX_SYSCALL_INTERRUPT_PRIORITY  10
 
/* 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. */
#define configKERNEL_INTERRUPT_PRIORITY               (configLIBRARY_LOWEST_INTERRUPT_PRIORITY << (8 - configPRIO_BITS))
/* !!!! configMAX_SYSCALL_INTERRUPT_PRIORITY must not be set to zero !!!!
See http://www.FreeRTOS.org/RTOS-Cortex-M3-M4.html. */
#define configMAX_SYSCALL_INTERRUPT_PRIORITY          (configLIBRARY_MAX_SYSCALL_INTERRUPT_PRIORITY << (8 - configPRIO_BITS))
 
/* 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"
 
#endif /* FREERTOS_CONFIG_H */

Below is what I get in the Debug printf window when I run the application:

starting Main() initialize Leds Create Semaphore Handle Creating Tasks Starting Task Scheduler

So to me it appears that the task scheduler is starting but none of the tasks are firing. I am thinking the tasks are in a blocking state for some reason but can't figure out why. Also if I remove all the semaphore code the application works as desired. All the Leds blink. As soon as I add the semaphore code it is broke again. Please help me figure out why? Thank you!

[David Littell]

gatekeeper's type should be SemaphoreHandle_t, right? Consider that someone might need to do an initial give...

[David Littell]

You probably need to get the system tick going.

[Paul Leslie]

Thanks I will try your suggestions

[Paul Leslie]

I changed gatekeeper to SemaphoreHandle_t and it still will not run any of the tasks. As for the system tick if that was the issue then my code should not work with all code related to Semaphore removed correct? You may have missed it in my original post but with all semaphore code removed the code works as desired. It appears as the Task scheduler is starting because if I pause the code in debug and start stepping through it then it keeps going through the idle task function. So for some reason all the tasks are blocking for some reason, I think. As I said I am still learning so any input would be appreciated.

[Aasee.2]

I will try and mirror this and dig thru the C books - in the imply time I observe you aren't using the modern model of GCC, and the model you're the usage of is marked as pre-launch (i.E. Now not necessarily a strong launch) and review. Please attempt the same experiment with the modern day solid GCC launch (5.2?) and document again your findings. I will do likewise.