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FreeRTOS V5.4.2 - Copyright (C) 2009 Real Time Engineers Ltd.
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FreeRTOS is free software; you can redistribute it and/or modify it under
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**NOTE** The exception to the GPL is included to allow you to distribute a
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* *
* Looking for a quick start? Then check out the FreeRTOS eBook! *
* See for details *
* *
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* Create a single persistent task which periodically dynamically creates another
* four tasks. The original task is called the creator task, the four tasks it
* creates are called suicidal tasks.
* Two of the created suicidal tasks kill one other suicidal task before killing
* themselves - leaving just the original task remaining.
* The creator task must be spawned after all of the other demo application tasks
* as it keeps a check on the number of tasks under the scheduler control. The
* number of tasks it expects to see running should never be greater than the
* number of tasks that were in existence when the creator task was spawned, plus
* one set of four suicidal tasks. If this number is exceeded an error is flagged.
* \page DeathC death.c
* \ingroup DemoFiles
* <HR>
Changes from V2.0.0
+ Delay periods are now specified using variables and constants of
portTickType rather than unsigned portLONG.
#include <stdlib.h>
/* Scheduler include files. */
#include "FreeRTOS.h"
#include "task.h"
/* Demo program include files. */
#include "death.h"
#include "print.h"
#define deathSTACK_SIZE ( ( unsigned portSHORT ) 512 )
/* The task originally created which is responsible for periodically dynamically
creating another four tasks. */
static void vCreateTasks( void *pvParameters );
/* The task function of the dynamically created tasks. */
static void vSuicidalTask( void *pvParameters );
/* A variable which is incremented every time the dynamic tasks are created. This
is used to check that the task is still running. */
static volatile portSHORT sCreationCount = 0;
/* Used to store the number of tasks that were originally running so the creator
task can tell if any of the suicidal tasks have failed to die. */
static volatile unsigned portBASE_TYPE uxTasksRunningAtStart = 0;
static const unsigned portBASE_TYPE uxMaxNumberOfExtraTasksRunning = 5;
/* Used to store a handle to the tasks that should be killed by a suicidal task,
before it kills itself. */
xTaskHandle xCreatedTask1, xCreatedTask2;
void vCreateSuicidalTasks( unsigned portBASE_TYPE uxPriority )
unsigned portBASE_TYPE *puxPriority;
/* Create the Creator tasks - passing in as a parameter the priority at which
the suicidal tasks should be created. */
puxPriority = ( unsigned portBASE_TYPE * ) pvPortMalloc( sizeof( unsigned portBASE_TYPE ) );
*puxPriority = uxPriority;
xTaskCreate( vCreateTasks, "CREATOR", deathSTACK_SIZE, ( void * ) puxPriority, uxPriority, NULL );
/* Record the number of tasks that are running now so we know if any of the
suicidal tasks have failed to be killed. */
uxTasksRunningAtStart = uxTaskGetNumberOfTasks();
static void vSuicidalTask( void *pvParameters )
portDOUBLE d1, d2;
xTaskHandle xTaskToKill;
const portTickType xDelay = ( portTickType ) 500 / portTICK_RATE_MS;
if( pvParameters != NULL )
/* This task is periodically created four times. Tow created tasks are
passed a handle to the other task so it can kill it before killing itself.
The other task is passed in null. */
xTaskToKill = *( xTaskHandle* )pvParameters;
xTaskToKill = NULL;
for( ;; )
/* Do something random just to use some stack and registers. */
d1 = 2.4;
d2 = 89.2;
d2 *= d1;
vTaskDelay( xDelay );
if( xTaskToKill != NULL )
/* Make sure the other task has a go before we delete it. */
vTaskDelay( ( portTickType ) 0 );
/* Kill the other task that was created by vCreateTasks(). */
vTaskDelete( xTaskToKill );
/* Kill ourselves. */
vTaskDelete( NULL );
}/*lint !e818 !e550 Function prototype must be as per standard for task functions. */
static void vCreateTasks( void *pvParameters )
const portTickType xDelay = ( portTickType ) 1000 / portTICK_RATE_MS;
unsigned portBASE_TYPE uxPriority;
const portCHAR * const pcTaskStartMsg = "Create task started.\r\n";
/* Queue a message for printing to say the task has started. */
vPrintDisplayMessage( &pcTaskStartMsg );
uxPriority = *( unsigned portBASE_TYPE * ) pvParameters;
vPortFree( pvParameters );
for( ;; )
/* Just loop round, delaying then creating the four suicidal tasks. */
vTaskDelay( xDelay );
xTaskCreate( vSuicidalTask, "SUICIDE1", deathSTACK_SIZE, NULL, uxPriority, &xCreatedTask1 );
xTaskCreate( vSuicidalTask, "SUICIDE2", deathSTACK_SIZE, &xCreatedTask1, uxPriority, NULL );
xTaskCreate( vSuicidalTask, "SUICIDE1", deathSTACK_SIZE, NULL, uxPriority, &xCreatedTask2 );
xTaskCreate( vSuicidalTask, "SUICIDE2", deathSTACK_SIZE, &xCreatedTask2, uxPriority, NULL );
/* This is called to check that the creator task is still running and that there
are not any more than four extra tasks. */
portBASE_TYPE xIsCreateTaskStillRunning( void )
static portSHORT sLastCreationCount = 0;
portSHORT sReturn = pdTRUE;
unsigned portBASE_TYPE uxTasksRunningNow;
if( sLastCreationCount == sCreationCount )
sReturn = pdFALSE;
uxTasksRunningNow = uxTaskGetNumberOfTasks();
if( uxTasksRunningNow < uxTasksRunningAtStart )
sReturn = pdFALSE;
else if( ( uxTasksRunningNow - uxTasksRunningAtStart ) > uxMaxNumberOfExtraTasksRunning )
sReturn = pdFALSE;
/* Everything is okay. */
return sReturn;