2 FreeRTOS.org V5.1.0 - Copyright (C) 2003-2008 Richard Barry.
\r
4 This file is part of the FreeRTOS.org distribution.
\r
6 FreeRTOS.org is free software; you can redistribute it and/or modify
\r
7 it under the terms of the GNU General Public License as published by
\r
8 the Free Software Foundation; either version 2 of the License, or
\r
9 (at your option) any later version.
\r
11 FreeRTOS.org is distributed in the hope that it will be useful,
\r
12 but WITHOUT ANY WARRANTY; without even the implied warranty of
\r
13 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
\r
14 GNU General Public License for more details.
\r
16 You should have received a copy of the GNU General Public License
\r
17 along with FreeRTOS.org; if not, write to the Free Software
\r
18 Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
\r
20 A special exception to the GPL can be applied should you wish to distribute
\r
21 a combined work that includes FreeRTOS.org, without being obliged to provide
\r
22 the source code for any proprietary components. See the licensing section
\r
23 of http://www.FreeRTOS.org for full details of how and when the exception
\r
26 ***************************************************************************
\r
27 ***************************************************************************
\r
29 * SAVE TIME AND MONEY! We can port FreeRTOS.org to your own hardware, *
\r
30 * and even write all or part of your application on your behalf. *
\r
31 * See http://www.OpenRTOS.com for details of the services we provide to *
\r
32 * expedite your project. *
\r
34 ***************************************************************************
\r
35 ***************************************************************************
\r
37 Please ensure to read the configuration and relevant port sections of the
\r
38 online documentation.
\r
40 http://www.FreeRTOS.org - Documentation, latest information, license and
\r
43 http://www.SafeRTOS.com - A version that is certified for use in safety
\r
46 http://www.OpenRTOS.com - Commercial support, development, porting,
\r
47 licensing and training services.
\r
51 * Creates two sets of two tasks. The tasks within a set share a variable, access
\r
52 * to which is guarded by a semaphore.
\r
54 * Each task starts by attempting to obtain the semaphore. On obtaining a
\r
55 * semaphore a task checks to ensure that the guarded variable has an expected
\r
56 * value. It then clears the variable to zero before counting it back up to the
\r
57 * expected value in increments of 1. After each increment the variable is checked
\r
58 * to ensure it contains the value to which it was just set. When the starting
\r
59 * value is again reached the task releases the semaphore giving the other task in
\r
60 * the set a chance to do exactly the same thing. The starting value is high
\r
61 * enough to ensure that a tick is likely to occur during the incrementing loop.
\r
63 * An error is flagged if at any time during the process a shared variable is
\r
64 * found to have a value other than that expected. Such an occurrence would
\r
65 * suggest an error in the mutual exclusion mechanism by which access to the
\r
66 * variable is restricted.
\r
68 * The first set of two tasks poll their semaphore. The second set use blocking
\r
76 /* Scheduler include files. */
\r
77 #include "FreeRTOS.h"
\r
81 /* Demo app include files. */
\r
82 #include "semtest.h"
\r
84 /* The value to which the shared variables are counted. */
\r
85 #define semtstBLOCKING_EXPECTED_VALUE ( ( unsigned portLONG ) 0xfff )
\r
86 #define semtstNON_BLOCKING_EXPECTED_VALUE ( ( unsigned portLONG ) 0xff )
\r
88 #define semtstSTACK_SIZE configMINIMAL_STACK_SIZE
\r
90 #define semtstNUM_TASKS ( 4 )
\r
92 #define semtstDELAY_FACTOR ( ( portTickType ) 10 )
\r
94 /* The task function as described at the top of the file. */
\r
95 static portTASK_FUNCTION_PROTO( prvSemaphoreTest, pvParameters );
\r
97 /* Structure used to pass parameters to each task. */
\r
98 typedef struct SEMAPHORE_PARAMETERS
\r
100 xSemaphoreHandle xSemaphore;
\r
101 volatile unsigned portLONG *pulSharedVariable;
\r
102 portTickType xBlockTime;
\r
103 } xSemaphoreParameters;
\r
105 /* Variables used to check that all the tasks are still running without errors. */
\r
106 static volatile portSHORT sCheckVariables[ semtstNUM_TASKS ] = { 0 };
\r
107 static volatile portSHORT sNextCheckVariable = 0;
\r
109 /*-----------------------------------------------------------*/
\r
111 void vStartSemaphoreTasks( unsigned portBASE_TYPE uxPriority )
\r
113 xSemaphoreParameters *pxFirstSemaphoreParameters, *pxSecondSemaphoreParameters;
\r
114 const portTickType xBlockTime = ( portTickType ) 100;
\r
116 /* Create the structure used to pass parameters to the first two tasks. */
\r
117 pxFirstSemaphoreParameters = ( xSemaphoreParameters * ) pvPortMalloc( sizeof( xSemaphoreParameters ) );
\r
119 if( pxFirstSemaphoreParameters != NULL )
\r
121 /* Create the semaphore used by the first two tasks. */
\r
122 vSemaphoreCreateBinary( pxFirstSemaphoreParameters->xSemaphore );
\r
124 if( pxFirstSemaphoreParameters->xSemaphore != NULL )
\r
126 /* Create the variable which is to be shared by the first two tasks. */
\r
127 pxFirstSemaphoreParameters->pulSharedVariable = ( unsigned portLONG * ) pvPortMalloc( sizeof( unsigned portLONG ) );
\r
129 /* Initialise the share variable to the value the tasks expect. */
\r
130 *( pxFirstSemaphoreParameters->pulSharedVariable ) = semtstNON_BLOCKING_EXPECTED_VALUE;
\r
132 /* The first two tasks do not block on semaphore calls. */
\r
133 pxFirstSemaphoreParameters->xBlockTime = ( portTickType ) 0;
\r
135 /* Spawn the first two tasks. As they poll they operate at the idle priority. */
\r
136 xTaskCreate( prvSemaphoreTest, ( signed portCHAR * ) "PolSEM1", semtstSTACK_SIZE, ( void * ) pxFirstSemaphoreParameters, tskIDLE_PRIORITY, ( xTaskHandle * ) NULL );
\r
137 xTaskCreate( prvSemaphoreTest, ( signed portCHAR * ) "PolSEM2", semtstSTACK_SIZE, ( void * ) pxFirstSemaphoreParameters, tskIDLE_PRIORITY, ( xTaskHandle * ) NULL );
\r
141 /* Do exactly the same to create the second set of tasks, only this time
\r
142 provide a block time for the semaphore calls. */
\r
143 pxSecondSemaphoreParameters = ( xSemaphoreParameters * ) pvPortMalloc( sizeof( xSemaphoreParameters ) );
\r
144 if( pxSecondSemaphoreParameters != NULL )
\r
146 vSemaphoreCreateBinary( pxSecondSemaphoreParameters->xSemaphore );
\r
148 if( pxSecondSemaphoreParameters->xSemaphore != NULL )
\r
150 pxSecondSemaphoreParameters->pulSharedVariable = ( unsigned portLONG * ) pvPortMalloc( sizeof( unsigned portLONG ) );
\r
151 *( pxSecondSemaphoreParameters->pulSharedVariable ) = semtstBLOCKING_EXPECTED_VALUE;
\r
152 pxSecondSemaphoreParameters->xBlockTime = xBlockTime / portTICK_RATE_MS;
\r
154 xTaskCreate( prvSemaphoreTest, ( signed portCHAR * ) "BlkSEM1", semtstSTACK_SIZE, ( void * ) pxSecondSemaphoreParameters, uxPriority, ( xTaskHandle * ) NULL );
\r
155 xTaskCreate( prvSemaphoreTest, ( signed portCHAR * ) "BlkSEM2", semtstSTACK_SIZE, ( void * ) pxSecondSemaphoreParameters, uxPriority, ( xTaskHandle * ) NULL );
\r
159 /* vQueueAddToRegistry() adds the semaphore to the registry, if one is
\r
160 in use. The registry is provided as a means for kernel aware
\r
161 debuggers to locate semaphores and has no purpose if a kernel aware debugger
\r
162 is not being used. The call to vQueueAddToRegistry() will be removed
\r
163 by the pre-processor if configQUEUE_REGISTRY_SIZE is not defined or is
\r
164 defined to be less than 1. */
\r
165 vQueueAddToRegistry( ( xQueueHandle ) pxFirstSemaphoreParameters->xSemaphore, ( signed portCHAR * ) "Counting_Sem_1" );
\r
166 vQueueAddToRegistry( ( xQueueHandle ) pxSecondSemaphoreParameters->xSemaphore, ( signed portCHAR * ) "Counting_Sem_2" );
\r
168 /*-----------------------------------------------------------*/
\r
170 static portTASK_FUNCTION( prvSemaphoreTest, pvParameters )
\r
172 xSemaphoreParameters *pxParameters;
\r
173 volatile unsigned portLONG *pulSharedVariable, ulExpectedValue;
\r
174 unsigned portLONG ulCounter;
\r
175 portSHORT sError = pdFALSE, sCheckVariableToUse;
\r
177 /* See which check variable to use. sNextCheckVariable is not semaphore
\r
179 portENTER_CRITICAL();
\r
180 sCheckVariableToUse = sNextCheckVariable;
\r
181 sNextCheckVariable++;
\r
182 portEXIT_CRITICAL();
\r
184 /* A structure is passed in as the parameter. This contains the shared
\r
185 variable being guarded. */
\r
186 pxParameters = ( xSemaphoreParameters * ) pvParameters;
\r
187 pulSharedVariable = pxParameters->pulSharedVariable;
\r
189 /* If we are blocking we use a much higher count to ensure loads of context
\r
190 switches occur during the count. */
\r
191 if( pxParameters->xBlockTime > ( portTickType ) 0 )
\r
193 ulExpectedValue = semtstBLOCKING_EXPECTED_VALUE;
\r
197 ulExpectedValue = semtstNON_BLOCKING_EXPECTED_VALUE;
\r
202 /* Try to obtain the semaphore. */
\r
203 if( xSemaphoreTake( pxParameters->xSemaphore, pxParameters->xBlockTime ) == pdPASS )
\r
205 /* We have the semaphore and so expect any other tasks using the
\r
206 shared variable to have left it in the state we expect to find
\r
208 if( *pulSharedVariable != ulExpectedValue )
\r
213 /* Clear the variable, then count it back up to the expected value
\r
214 before releasing the semaphore. Would expect a context switch or
\r
215 two during this time. */
\r
216 for( ulCounter = ( unsigned portLONG ) 0; ulCounter <= ulExpectedValue; ulCounter++ )
\r
218 *pulSharedVariable = ulCounter;
\r
219 if( *pulSharedVariable != ulCounter )
\r
225 /* Release the semaphore, and if no errors have occurred increment the check
\r
227 if( xSemaphoreGive( pxParameters->xSemaphore ) == pdFALSE )
\r
232 if( sError == pdFALSE )
\r
234 if( sCheckVariableToUse < semtstNUM_TASKS )
\r
236 ( sCheckVariables[ sCheckVariableToUse ] )++;
\r
240 /* If we have a block time then we are running at a priority higher
\r
241 than the idle priority. This task takes a long time to complete
\r
242 a cycle (deliberately so to test the guarding) so will be starving
\r
243 out lower priority tasks. Block for some time to allow give lower
\r
244 priority tasks some processor time. */
\r
245 vTaskDelay( pxParameters->xBlockTime * semtstDELAY_FACTOR );
\r
249 if( pxParameters->xBlockTime == ( portTickType ) 0 )
\r
251 /* We have not got the semaphore yet, so no point using the
\r
252 processor. We are not blocking when attempting to obtain the
\r
259 /*-----------------------------------------------------------*/
\r
261 /* This is called to check that all the created tasks are still running. */
\r
262 portBASE_TYPE xAreSemaphoreTasksStillRunning( void )
\r
264 static portSHORT sLastCheckVariables[ semtstNUM_TASKS ] = { 0 };
\r
265 portBASE_TYPE xTask, xReturn = pdTRUE;
\r
267 for( xTask = 0; xTask < semtstNUM_TASKS; xTask++ )
\r
269 if( sLastCheckVariables[ xTask ] == sCheckVariables[ xTask ] )
\r
274 sLastCheckVariables[ xTask ] = sCheckVariables[ xTask ];
\r