FreeRTOS/Common/Minimal/death.c

   1 /*
   2     FreeRTOS V6.0.5 - Copyright (C) 2010 Real Time Engineers Ltd.
   3
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  24
  25     This file is part of the FreeRTOS distribution.
  26
  27     FreeRTOS is free software; you can redistribute it and/or modify it under
  28     the terms of the GNU General Public License (version 2) as published by the
  29     Free Software Foundation AND MODIFIED BY the FreeRTOS exception.
  30     ***NOTE*** The exception to the GPL is included to allow you to distribute
  31     a combined work that includes FreeRTOS without being obliged to provide the
  32     source code for proprietary components outside of the FreeRTOS kernel.
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  35     FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
  36     more details. You should have received a copy of the GNU General Public
  37     License and the FreeRTOS license exception along with FreeRTOS; if not it
  38     can be viewed here: http://www.freertos.org/a00114.html and also obtained
  39     by writing to Richard Barry, contact details for whom are available on the
  40     FreeRTOS WEB site.
  41
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  52 */
  53
  54 /**
  55  * Create a single persistent task which periodically dynamically creates another
  56  * two tasks.  The original task is called the creator task, the two tasks it
  57  * creates are called suicidal tasks.
  58  *
  59  * One of the created suicidal tasks kill one other suicidal task before killing
  60  * itself - leaving just the original task remaining.
  61  *
  62  * The creator task must be spawned after all of the other demo application tasks
  63  * as it keeps a check on the number of tasks under the scheduler control.  The
  64  * number of tasks it expects to see running should never be greater than the
  65  * number of tasks that were in existence when the creator task was spawned, plus
  66  * one set of four suicidal tasks.  If this number is exceeded an error is flagged.
  67  *
  68  * \page DeathC death.c
  69  * \ingroup DemoFiles
  70  * <HR>
  71  */
  72
  73 /*
  74 Changes from V3.0.0
  75         + CreationCount sizes changed from unsigned portBASE_TYPE to
  76           unsigned short to minimize the risk of overflowing.
  77
  78         + Reset of usLastCreationCount added
  79
  80 Changes from V3.1.0
  81         + Changed the dummy calculation to use variables of type long, rather than
  82           float.  This allows the file to be used with ports that do not support
  83           floating point.
  84
  85 */
  86
  87 #include <stdlib.h>
  88
  89 /* Scheduler include files. */
  90 #include "FreeRTOS.h"
  91 #include "task.h"
  92
  93 /* Demo program include files. */
  94 #include "death.h"
  95
  96 #define deathSTACK_SIZE         ( configMINIMAL_STACK_SIZE + 60 )
  97
  98 /* The task originally created which is responsible for periodically dynamically
  99 creating another four tasks. */
 100 static portTASK_FUNCTION_PROTO( vCreateTasks, pvParameters );
 101
 102 /* The task function of the dynamically created tasks. */
 103 static portTASK_FUNCTION_PROTO( vSuicidalTask, pvParameters );
 104
 105 /* A variable which is incremented every time the dynamic tasks are created.  This
 106 is used to check that the task is still running. */
 107 static volatile unsigned short usCreationCount = 0;
 108
 109 /* Used to store the number of tasks that were originally running so the creator
 110 task can tell if any of the suicidal tasks have failed to die.
 111 */
 112 static volatile unsigned portBASE_TYPE uxTasksRunningAtStart = 0;
 113
 114 /* Tasks are deleted by the idle task.  Under heavy load the idle task might
 115 not get much processing time, so it would be legitimate for several tasks to
 116 remain undeleted for a short period. */
 117 static const unsigned portBASE_TYPE uxMaxNumberOfExtraTasksRunning = 2;
 118
 119 /* Used to store a handle to the task that should be killed by a suicidal task,
 120 before it kills itself. */
 121 xTaskHandle xCreatedTask;
 122
 123 /*-----------------------------------------------------------*/
 124
 125 void vCreateSuicidalTasks( unsigned portBASE_TYPE uxPriority )
 126 {
 127 unsigned portBASE_TYPE *puxPriority;
 128
 129         /* Create the Creator tasks - passing in as a parameter the priority at which
 130         the suicidal tasks should be created. */
 131         puxPriority = ( unsigned portBASE_TYPE * ) pvPortMalloc( sizeof( unsigned portBASE_TYPE ) );
 132         *puxPriority = uxPriority;
 133
 134         xTaskCreate( vCreateTasks, ( signed char * ) "CREATOR", deathSTACK_SIZE, ( void * ) puxPriority, uxPriority, NULL );
 135
 136         /* Record the number of tasks that are running now so we know if any of the
 137         suicidal tasks have failed to be killed. */
 138         uxTasksRunningAtStart = ( unsigned portBASE_TYPE ) uxTaskGetNumberOfTasks();
 139
 140         /* FreeRTOS.org versions before V3.0 started the idle-task as the very
 141         first task. The idle task was then already included in uxTasksRunningAtStart.
 142         From FreeRTOS V3.0 on, the idle task is started when the scheduler is
 143         started. Therefore the idle task is not yet accounted for. We correct
 144         this by increasing uxTasksRunningAtStart by 1. */
 145         uxTasksRunningAtStart++;
 146 }
 147 /*-----------------------------------------------------------*/
 148
 149 static portTASK_FUNCTION( vSuicidalTask, pvParameters )
 150 {
 151 volatile long l1, l2;
 152 xTaskHandle xTaskToKill;
 153 const portTickType xDelay = ( portTickType ) 200 / portTICK_RATE_MS;
 154
 155         if( pvParameters != NULL )
 156         {
 157                 /* This task is periodically created four times.  Two created tasks are
 158                 passed a handle to the other task so it can kill it before killing itself.
 159                 The other task is passed in null. */
 160                 xTaskToKill = *( xTaskHandle* )pvParameters;
 161         }
 162         else
 163         {
 164                 xTaskToKill = NULL;
 165         }
 166
 167         for( ;; )
 168         {
 169                 /* Do something random just to use some stack and registers. */
 170                 l1 = 2;
 171                 l2 = 89;
 172                 l2 *= l1;
 173                 vTaskDelay( xDelay );
 174
 175                 if( xTaskToKill != NULL )
 176                 {
 177                         /* Make sure the other task has a go before we delete it. */
 178                         vTaskDelay( ( portTickType ) 0 );
 179
 180                         /* Kill the other task that was created by vCreateTasks(). */
 181                         vTaskDelete( xTaskToKill );
 182
 183                         /* Kill ourselves. */
 184                         vTaskDelete( NULL );
 185                 }
 186         }
 187 }/*lint !e818 !e550 Function prototype must be as per standard for task functions. */
 188 /*-----------------------------------------------------------*/
 189
 190 static portTASK_FUNCTION( vCreateTasks, pvParameters )
 191 {
 192 const portTickType xDelay = ( portTickType ) 1000 / portTICK_RATE_MS;
 193 unsigned portBASE_TYPE uxPriority;
 194
 195         uxPriority = *( unsigned portBASE_TYPE * ) pvParameters;
 196         vPortFree( pvParameters );
 197
 198         for( ;; )
 199         {
 200                 /* Just loop round, delaying then creating the four suicidal tasks. */
 201                 vTaskDelay( xDelay );
 202
 203                 xCreatedTask = NULL;
 204
 205                 xTaskCreate( vSuicidalTask, ( signed char * ) "SUICID1", configMINIMAL_STACK_SIZE, NULL, uxPriority, &xCreatedTask );
 206                 xTaskCreate( vSuicidalTask, ( signed char * ) "SUICID2", configMINIMAL_STACK_SIZE, &xCreatedTask, uxPriority, NULL );
 207
 208                 ++usCreationCount;
 209         }
 210 }
 211 /*-----------------------------------------------------------*/
 212
 213 /* This is called to check that the creator task is still running and that there
 214 are not any more than four extra tasks. */
 215 portBASE_TYPE xIsCreateTaskStillRunning( void )
 216 {
 217 static unsigned short usLastCreationCount = 0xfff;
 218 portBASE_TYPE xReturn = pdTRUE;
 219 static unsigned portBASE_TYPE uxTasksRunningNow;
 220
 221         if( usLastCreationCount == usCreationCount )
 222         {
 223                 xReturn = pdFALSE;
 224         }
 225         else
 226         {
 227                 usLastCreationCount = usCreationCount;
 228         }
 229
 230         uxTasksRunningNow = ( unsigned portBASE_TYPE ) uxTaskGetNumberOfTasks();
 231
 232         if( uxTasksRunningNow < uxTasksRunningAtStart )
 233         {
 234                 xReturn = pdFALSE;
 235         }
 236         else if( ( uxTasksRunningNow - uxTasksRunningAtStart ) > uxMaxNumberOfExtraTasksRunning )
 237         {
 238                 xReturn = pdFALSE;
 239         }
 240         else
 241         {
 242                 /* Everything is okay. */
 243         }
 244
 245         return xReturn;
 246 }
 247
 248