FreeRTOS/Demo/Common/Minimal/QPeek.c - third_party/github/FreeRTOS/FreeRTOS-Kernel - Git at Google

 /*
  * FreeRTOS Kernel V10.3.0
  * Copyright (C) 2020 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!
  */


 /*
  * Tests the behaviour when data is peeked from a queue when there are
  * multiple tasks blocked on the queue.
  */


 #include <stdlib.h>

 /* Scheduler include files. */
 #include "FreeRTOS.h"
 #include "task.h"
 #include "queue.h"
 #include "semphr.h"

 /* Demo program include files. */
 #include "QPeek.h"

 #define qpeekQUEUE_LENGTH		( 5 )
 #define qpeekNO_BLOCK			( 0 )
 #define qpeekSHORT_DELAY		( 10 )

 #define qpeekLOW_PRIORITY			( tskIDLE_PRIORITY + 0 )
 #define qpeekMEDIUM_PRIORITY		( tskIDLE_PRIORITY + 1 )
 #define qpeekHIGH_PRIORITY			( tskIDLE_PRIORITY + 2 )
 #define qpeekHIGHEST_PRIORITY		( tskIDLE_PRIORITY + 3 )

 /*-----------------------------------------------------------*/

 /*
  * The following three tasks are used to demonstrate the peeking behaviour.
  * Each task is given a different priority to demonstrate the order in which
  * tasks are woken as data is peeked from a queue.
  */
 static void prvLowPriorityPeekTask( void *pvParameters );
 static void prvMediumPriorityPeekTask( void *pvParameters );
 static void prvHighPriorityPeekTask( void *pvParameters );
 static void prvHighestPriorityPeekTask( void *pvParameters );

 /*-----------------------------------------------------------*/

 /* Flag that will be latched to pdTRUE should any unexpected behaviour be
 detected in any of the tasks. */
 static volatile BaseType_t xErrorDetected = pdFALSE;

 /* Counter that is incremented on each cycle of a test.  This is used to
 detect a stalled task - a test that is no longer running. */
 static volatile uint32_t ulLoopCounter = 0;

 /* Handles to the test tasks. */
 TaskHandle_t xMediumPriorityTask, xHighPriorityTask, xHighestPriorityTask;
 /*-----------------------------------------------------------*/

 void vStartQueuePeekTasks( void )
 {
 QueueHandle_t xQueue;

 	/* Create the queue that we are going to use for the test/demo. */
 	xQueue = xQueueCreate( qpeekQUEUE_LENGTH, sizeof( uint32_t ) );

 	if( xQueue != NULL )
 	{
 		/* vQueueAddToRegistry() adds the queue to the queue registry, if one is
 		in use.  The queue registry is provided as a means for kernel aware
 		debuggers to locate queues and has no purpose if a kernel aware debugger
 		is not being used.  The call to vQueueAddToRegistry() will be removed
 		by the pre-processor if configQUEUE_REGISTRY_SIZE is not defined or is
 		defined to be less than 1. */
 		vQueueAddToRegistry( xQueue, "QPeek_Test_Queue" );

 		/* Create the demo tasks and pass it the queue just created.  We are
 		passing the queue handle by value so it does not matter that it is declared
 		on the stack here. */
 		xTaskCreate( prvLowPriorityPeekTask, "PeekL", configMINIMAL_STACK_SIZE, ( void * ) xQueue, qpeekLOW_PRIORITY, NULL );
 		xTaskCreate( prvMediumPriorityPeekTask, "PeekM", configMINIMAL_STACK_SIZE, ( void * ) xQueue, qpeekMEDIUM_PRIORITY, &xMediumPriorityTask );
 		xTaskCreate( prvHighPriorityPeekTask, "PeekH1", configMINIMAL_STACK_SIZE, ( void * ) xQueue, qpeekHIGH_PRIORITY, &xHighPriorityTask );
 		xTaskCreate( prvHighestPriorityPeekTask, "PeekH2", configMINIMAL_STACK_SIZE, ( void * ) xQueue, qpeekHIGHEST_PRIORITY, &xHighestPriorityTask );
 	}
 }
 /*-----------------------------------------------------------*/

 static void prvHighestPriorityPeekTask( void *pvParameters )
 {
 QueueHandle_t xQueue = ( QueueHandle_t ) pvParameters;
 uint32_t ulValue;

 	#ifdef USE_STDIO
 	{
 		void vPrintDisplayMessage( const char * const * ppcMessageToSend );

 		const char * const pcTaskStartMsg = "Queue peek test started.\r\n";

 		/* Queue a message for printing to say the task has started. */
 		vPrintDisplayMessage( &pcTaskStartMsg );
 	}
 	#endif

 	for( ;; )
 	{
 		/* Try peeking from the queue.  The queue should be empty so we will
 		block, allowing the high priority task to execute. */
 		if( xQueuePeek( xQueue, &ulValue, portMAX_DELAY ) != pdPASS )
 		{
 			/* We expected to have received something by the time we unblock. */
 			xErrorDetected = pdTRUE;
 		}

 		/* When we reach here the high and medium priority tasks should still
 		be blocked on the queue.  We unblocked because the low priority task
 		wrote a value to the queue, which we should have peeked.  Peeking the
 		data (rather than receiving it) will leave the data on the queue, so
 		the high priority task should then have also been unblocked, but not
 		yet executed. */
 		if( ulValue != 0x11223344 )
 		{
 			/* We did not receive the expected value. */
 			xErrorDetected = pdTRUE;
 		}

 		if( uxQueueMessagesWaiting( xQueue ) != 1 )
 		{
 			/* The message should have been left on the queue. */
 			xErrorDetected = pdTRUE;
 		}

 		/* Now we are going to actually receive the data, so when the high
 		priority task runs it will find the queue empty and return to the
 		blocked state. */
 		ulValue = 0;
 		if( xQueueReceive( xQueue, &ulValue, qpeekNO_BLOCK ) != pdPASS )
 		{
 			/* We expected to receive the value. */
 			xErrorDetected = pdTRUE;
 		}

 		if( ulValue != 0x11223344 )
 		{
 			/* We did not receive the expected value - which should have been
 			the same value as was peeked. */
 			xErrorDetected = pdTRUE;
 		}

 		/* Now we will block again as the queue is once more empty.  The low
 		priority task can then execute again. */
 		if( xQueuePeek( xQueue, &ulValue, portMAX_DELAY ) != pdPASS )
 		{
 			/* We expected to have received something by the time we unblock. */
 			xErrorDetected = pdTRUE;
 		}

 		/* When we get here the low priority task should have again written to the
 		queue. */
 		if( ulValue != 0x01234567 )
 		{
 			/* We did not receive the expected value. */
 			xErrorDetected = pdTRUE;
 		}

 		if( uxQueueMessagesWaiting( xQueue ) != 1 )
 		{
 			/* The message should have been left on the queue. */
 			xErrorDetected = pdTRUE;
 		}

 		/* We only peeked the data, so suspending ourselves now should enable
 		the high priority task to also peek the data.  The high priority task
 		will have been unblocked when we peeked the data as we left the data
 		in the queue. */
 		vTaskSuspend( NULL );


 		/* This time we are going to do the same as the above test, but the
 		high priority task is going to receive the data, rather than peek it.
 		This means that the medium priority task should never peek the value. */
 		if( xQueuePeek( xQueue, &ulValue, portMAX_DELAY ) != pdPASS )
 		{
 			xErrorDetected = pdTRUE;
 		}

 		if( ulValue != 0xaabbaabb )
 		{
 			xErrorDetected = pdTRUE;
 		}

 		vTaskSuspend( NULL );
 	}
 }
 /*-----------------------------------------------------------*/

 static void prvHighPriorityPeekTask( void *pvParameters )
 {
 QueueHandle_t xQueue = ( QueueHandle_t ) pvParameters;
 uint32_t ulValue;

 	for( ;; )
 	{
 		/* Try peeking from the queue.  The queue should be empty so we will
 		block, allowing the medium priority task to execute.  Both the high
 		and highest priority tasks will then be blocked on the queue. */
 		if( xQueuePeek( xQueue, &ulValue, portMAX_DELAY ) != pdPASS )
 		{
 			/* We expected to have received something by the time we unblock. */
 			xErrorDetected = pdTRUE;
 		}

 		/* When we get here the highest priority task should have peeked the data
 		(unblocking this task) then suspended (allowing this task to also peek
 		the data). */
 		if( ulValue != 0x01234567 )
 		{
 			/* We did not receive the expected value. */
 			xErrorDetected = pdTRUE;
 		}

 		if( uxQueueMessagesWaiting( xQueue ) != 1 )
 		{
 			/* The message should have been left on the queue. */
 			xErrorDetected = pdTRUE;
 		}

 		/* We only peeked the data, so suspending ourselves now should enable
 		the medium priority task to also peek the data.  The medium priority task
 		will have been unblocked when we peeked the data as we left the data
 		in the queue. */
 		vTaskSuspend( NULL );


 		/* This time we are going actually receive the value, so the medium
 		priority task will never peek the data - we removed it from the queue. */
 		if( xQueueReceive( xQueue, &ulValue, portMAX_DELAY ) != pdPASS )
 		{
 			xErrorDetected = pdTRUE;
 		}

 		if( ulValue != 0xaabbaabb )
 		{
 			xErrorDetected = pdTRUE;
 		}

 		vTaskSuspend( NULL );
 	}
 }
 /*-----------------------------------------------------------*/

 static void prvMediumPriorityPeekTask( void *pvParameters )
 {
 QueueHandle_t xQueue = ( QueueHandle_t ) pvParameters;
 uint32_t ulValue;

 	for( ;; )
 	{
 		/* Try peeking from the queue.  The queue should be empty so we will
 		block, allowing the low priority task to execute.  The highest, high
 		and medium priority tasks will then all be blocked on the queue. */
 		if( xQueuePeek( xQueue, &ulValue, portMAX_DELAY ) != pdPASS )
 		{
 			/* We expected to have received something by the time we unblock. */
 			xErrorDetected = pdTRUE;
 		}

 		/* When we get here the high priority task should have peeked the data
 		(unblocking this task) then suspended (allowing this task to also peek
 		the data). */
 		if( ulValue != 0x01234567 )
 		{
 			/* We did not receive the expected value. */
 			xErrorDetected = pdTRUE;
 		}

 		if( uxQueueMessagesWaiting( xQueue ) != 1 )
 		{
 			/* The message should have been left on the queue. */
 			xErrorDetected = pdTRUE;
 		}

 		/* Just so we know the test is still running. */
 		ulLoopCounter++;

 		/* Now we can suspend ourselves so the low priority task can execute
 		again. */
 		vTaskSuspend( NULL );
 	}
 }
 /*-----------------------------------------------------------*/

 static void prvLowPriorityPeekTask( void *pvParameters )
 {
 QueueHandle_t xQueue = ( QueueHandle_t ) pvParameters;
 uint32_t ulValue;

 	for( ;; )
 	{
 		/* Write some data to the queue.  This should unblock the highest
 		priority task that is waiting to peek data from the queue. */
 		ulValue = 0x11223344;
 		if( xQueueSendToBack( xQueue, &ulValue, qpeekNO_BLOCK ) != pdPASS )
 		{
 			/* We were expecting the queue to be empty so we should not of
 			had a problem writing to the queue. */
 			xErrorDetected = pdTRUE;
 		}

 		#if configUSE_PREEMPTION == 0
 			taskYIELD();
 		#endif

 		/* By the time we get here the data should have been removed from
 		the queue. */
 		if( uxQueueMessagesWaiting( xQueue ) != 0 )
 		{
 			xErrorDetected = pdTRUE;
 		}

 		/* Write another value to the queue, again waking the highest priority
 		task that is blocked on the queue. */
 		ulValue = 0x01234567;
 		if( xQueueSendToBack( xQueue, &ulValue, qpeekNO_BLOCK ) != pdPASS )
 		{
 			/* We were expecting the queue to be empty so we should not of
 			had a problem writing to the queue. */
 			xErrorDetected = pdTRUE;
 		}

 		#if configUSE_PREEMPTION == 0
 			taskYIELD();
 		#endif

 		/* All the other tasks should now have successfully peeked the data.
 		The data is still in the queue so we should be able to receive it. */
 		ulValue = 0;
 		if( xQueueReceive( xQueue, &ulValue, qpeekNO_BLOCK ) != pdPASS )
 		{
 			/* We expected to receive the data. */
 			xErrorDetected = pdTRUE;
 		}

 		if( ulValue != 0x01234567 )
 		{
 			/* We did not receive the expected value. */
 		}

 		/* Lets just delay a while as this is an intensive test as we don't
 		want to starve other tests of processing time. */
 		vTaskDelay( qpeekSHORT_DELAY );

 		/* Unsuspend the other tasks so we can repeat the test - this time
 		however not all the other tasks will peek the data as the high
 		priority task is actually going to remove it from the queue.  Send
 		to front is used just to be different.  As the queue is empty it
 		makes no difference to the result. */
 		vTaskResume( xMediumPriorityTask );
 		vTaskResume( xHighPriorityTask );
 		vTaskResume( xHighestPriorityTask );

 		#if( configUSE_PREEMPTION == 0 )
 			taskYIELD();
 		#endif

 		ulValue = 0xaabbaabb;
 		if( xQueueSendToFront( xQueue, &ulValue, qpeekNO_BLOCK ) != pdPASS )
 		{
 			/* We were expecting the queue to be empty so we should not of
 			had a problem writing to the queue. */
 			xErrorDetected = pdTRUE;
 		}

 		#if configUSE_PREEMPTION == 0
 			taskYIELD();
 		#endif

 		/* This time we should find that the queue is empty.  The high priority
 		task actually removed the data rather than just peeking it. */
 		if( xQueuePeek( xQueue, &ulValue, qpeekNO_BLOCK ) != errQUEUE_EMPTY )
 		{
 			/* We expected to receive the data. */
 			xErrorDetected = pdTRUE;
 		}

 		/* Unsuspend the highest and high priority tasks so we can go back
 		and repeat the whole thing.  The medium priority task should not be
 		suspended as it was not able to peek the data in this last case. */
 		vTaskResume( xHighPriorityTask );
 		vTaskResume( xHighestPriorityTask );

 		/* Lets just delay a while as this is an intensive test as we don't
 		want to starve other tests of processing time. */
 		vTaskDelay( qpeekSHORT_DELAY );
 	}
 }
 /*-----------------------------------------------------------*/

 /* This is called to check that all the created tasks are still running. */
 BaseType_t xAreQueuePeekTasksStillRunning( void )
 {
 static uint32_t ulLastLoopCounter = 0;

 	/* If the demo task is still running then we expect the loopcounter to
 	have incremented since this function was last called. */
 	if( ulLastLoopCounter == ulLoopCounter )
 	{
 		xErrorDetected = pdTRUE;
 	}

 	ulLastLoopCounter = ulLoopCounter;

 	/* Errors detected in the task itself will have latched xErrorDetected
 	to true. */

 	return ( BaseType_t ) !xErrorDetected;
 }
	/*
	* FreeRTOS Kernel V10.3.0
	* Copyright (C) 2020 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!
	*/


	/*
	* Tests the behaviour when data is peeked from a queue when there are
	* multiple tasks blocked on the queue.
	*/


	#include <stdlib.h>

	/* Scheduler include files. */
	#include "FreeRTOS.h"
	#include "task.h"
	#include "queue.h"
	#include "semphr.h"

	/* Demo program include files. */
	#include "QPeek.h"

	#define qpeekQUEUE_LENGTH ( 5 )
	#define qpeekNO_BLOCK ( 0 )
	#define qpeekSHORT_DELAY ( 10 )

	#define qpeekLOW_PRIORITY ( tskIDLE_PRIORITY + 0 )
	#define qpeekMEDIUM_PRIORITY ( tskIDLE_PRIORITY + 1 )
	#define qpeekHIGH_PRIORITY ( tskIDLE_PRIORITY + 2 )
	#define qpeekHIGHEST_PRIORITY ( tskIDLE_PRIORITY + 3 )

	/-----------------------------------------------------------/

	/*
	* The following three tasks are used to demonstrate the peeking behaviour.
	* Each task is given a different priority to demonstrate the order in which
	* tasks are woken as data is peeked from a queue.
	*/
	static void prvLowPriorityPeekTask( void *pvParameters );
	static void prvMediumPriorityPeekTask( void *pvParameters );
	static void prvHighPriorityPeekTask( void *pvParameters );
	static void prvHighestPriorityPeekTask( void *pvParameters );

	/-----------------------------------------------------------/

	/* Flag that will be latched to pdTRUE should any unexpected behaviour be
	detected in any of the tasks. */
	static volatile BaseType_t xErrorDetected = pdFALSE;

	/* Counter that is incremented on each cycle of a test. This is used to
	detect a stalled task - a test that is no longer running. */
	static volatile uint32_t ulLoopCounter = 0;

	/* Handles to the test tasks. */
	TaskHandle_t xMediumPriorityTask, xHighPriorityTask, xHighestPriorityTask;
	/-----------------------------------------------------------/

	void vStartQueuePeekTasks( void )
	{
	QueueHandle_t xQueue;

	/* Create the queue that we are going to use for the test/demo. */
	xQueue = xQueueCreate( qpeekQUEUE_LENGTH, sizeof( uint32_t ) );

	if( xQueue != NULL )
	{
	/* vQueueAddToRegistry() adds the queue to the queue registry, if one is
	in use. The queue registry is provided as a means for kernel aware
	debuggers to locate queues and has no purpose if a kernel aware debugger
	is not being used. The call to vQueueAddToRegistry() will be removed
	by the pre-processor if configQUEUE_REGISTRY_SIZE is not defined or is
	defined to be less than 1. */
	vQueueAddToRegistry( xQueue, "QPeek_Test_Queue" );

	/* Create the demo tasks and pass it the queue just created. We are
	passing the queue handle by value so it does not matter that it is declared
	on the stack here. */
	xTaskCreate( prvLowPriorityPeekTask, "PeekL", configMINIMAL_STACK_SIZE, ( void * ) xQueue, qpeekLOW_PRIORITY, NULL );
	xTaskCreate( prvMediumPriorityPeekTask, "PeekM", configMINIMAL_STACK_SIZE, ( void * ) xQueue, qpeekMEDIUM_PRIORITY, &xMediumPriorityTask );
	xTaskCreate( prvHighPriorityPeekTask, "PeekH1", configMINIMAL_STACK_SIZE, ( void * ) xQueue, qpeekHIGH_PRIORITY, &xHighPriorityTask );
	xTaskCreate( prvHighestPriorityPeekTask, "PeekH2", configMINIMAL_STACK_SIZE, ( void * ) xQueue, qpeekHIGHEST_PRIORITY, &xHighestPriorityTask );
	}
	}
	/-----------------------------------------------------------/

	static void prvHighestPriorityPeekTask( void *pvParameters )
	{
	QueueHandle_t xQueue = ( QueueHandle_t ) pvParameters;
	uint32_t ulValue;

	#ifdef USE_STDIO
	{
	void vPrintDisplayMessage( const char * const * ppcMessageToSend );

	const char * const pcTaskStartMsg = "Queue peek test started.\r\n";

	/* Queue a message for printing to say the task has started. */
	vPrintDisplayMessage( &pcTaskStartMsg );
	}
	#endif

	for( ;; )
	{
	/* Try peeking from the queue. The queue should be empty so we will
	block, allowing the high priority task to execute. */
	if( xQueuePeek( xQueue, &ulValue, portMAX_DELAY ) != pdPASS )
	{
	/* We expected to have received something by the time we unblock. */
	xErrorDetected = pdTRUE;
	}

	/* When we reach here the high and medium priority tasks should still
	be blocked on the queue. We unblocked because the low priority task
	wrote a value to the queue, which we should have peeked. Peeking the
	data (rather than receiving it) will leave the data on the queue, so
	the high priority task should then have also been unblocked, but not
	yet executed. */
	if( ulValue != 0x11223344 )
	{
	/* We did not receive the expected value. */
	xErrorDetected = pdTRUE;
	}

	if( uxQueueMessagesWaiting( xQueue ) != 1 )
	{
	/* The message should have been left on the queue. */
	xErrorDetected = pdTRUE;
	}

	/* Now we are going to actually receive the data, so when the high
	priority task runs it will find the queue empty and return to the
	blocked state. */
	ulValue = 0;
	if( xQueueReceive( xQueue, &ulValue, qpeekNO_BLOCK ) != pdPASS )
	{
	/* We expected to receive the value. */
	xErrorDetected = pdTRUE;
	}

	if( ulValue != 0x11223344 )
	{
	/* We did not receive the expected value - which should have been
	the same value as was peeked. */
	xErrorDetected = pdTRUE;
	}

	/* Now we will block again as the queue is once more empty. The low
	priority task can then execute again. */
	if( xQueuePeek( xQueue, &ulValue, portMAX_DELAY ) != pdPASS )
	{
	/* We expected to have received something by the time we unblock. */
	xErrorDetected = pdTRUE;
	}

	/* When we get here the low priority task should have again written to the
	queue. */
	if( ulValue != 0x01234567 )
	{
	/* We did not receive the expected value. */
	xErrorDetected = pdTRUE;
	}

	if( uxQueueMessagesWaiting( xQueue ) != 1 )
	{
	/* The message should have been left on the queue. */
	xErrorDetected = pdTRUE;
	}

	/* We only peeked the data, so suspending ourselves now should enable
	the high priority task to also peek the data. The high priority task
	will have been unblocked when we peeked the data as we left the data
	in the queue. */
	vTaskSuspend( NULL );



	/* This time we are going to do the same as the above test, but the
	high priority task is going to receive the data, rather than peek it.
	This means that the medium priority task should never peek the value. */
	if( xQueuePeek( xQueue, &ulValue, portMAX_DELAY ) != pdPASS )
	{
	xErrorDetected = pdTRUE;
	}

	if( ulValue != 0xaabbaabb )
	{
	xErrorDetected = pdTRUE;
	}

	vTaskSuspend( NULL );
	}
	}
	/-----------------------------------------------------------/

	static void prvHighPriorityPeekTask( void *pvParameters )
	{
	QueueHandle_t xQueue = ( QueueHandle_t ) pvParameters;
	uint32_t ulValue;

	for( ;; )
	{
	/* Try peeking from the queue. The queue should be empty so we will
	block, allowing the medium priority task to execute. Both the high
	and highest priority tasks will then be blocked on the queue. */
	if( xQueuePeek( xQueue, &ulValue, portMAX_DELAY ) != pdPASS )
	{
	/* We expected to have received something by the time we unblock. */
	xErrorDetected = pdTRUE;
	}

	/* When we get here the highest priority task should have peeked the data
	(unblocking this task) then suspended (allowing this task to also peek
	the data). */
	if( ulValue != 0x01234567 )
	{
	/* We did not receive the expected value. */
	xErrorDetected = pdTRUE;
	}

	if( uxQueueMessagesWaiting( xQueue ) != 1 )
	{
	/* The message should have been left on the queue. */
	xErrorDetected = pdTRUE;
	}

	/* We only peeked the data, so suspending ourselves now should enable
	the medium priority task to also peek the data. The medium priority task
	will have been unblocked when we peeked the data as we left the data
	in the queue. */
	vTaskSuspend( NULL );


	/* This time we are going actually receive the value, so the medium
	priority task will never peek the data - we removed it from the queue. */
	if( xQueueReceive( xQueue, &ulValue, portMAX_DELAY ) != pdPASS )
	{
	xErrorDetected = pdTRUE;
	}

	if( ulValue != 0xaabbaabb )
	{
	xErrorDetected = pdTRUE;
	}

	vTaskSuspend( NULL );
	}
	}
	/-----------------------------------------------------------/

	static void prvMediumPriorityPeekTask( void *pvParameters )
	{
	QueueHandle_t xQueue = ( QueueHandle_t ) pvParameters;
	uint32_t ulValue;

	for( ;; )
	{
	/* Try peeking from the queue. The queue should be empty so we will
	block, allowing the low priority task to execute. The highest, high
	and medium priority tasks will then all be blocked on the queue. */
	if( xQueuePeek( xQueue, &ulValue, portMAX_DELAY ) != pdPASS )
	{
	/* We expected to have received something by the time we unblock. */
	xErrorDetected = pdTRUE;
	}

	/* When we get here the high priority task should have peeked the data
	(unblocking this task) then suspended (allowing this task to also peek
	the data). */
	if( ulValue != 0x01234567 )
	{
	/* We did not receive the expected value. */
	xErrorDetected = pdTRUE;
	}

	if( uxQueueMessagesWaiting( xQueue ) != 1 )
	{
	/* The message should have been left on the queue. */
	xErrorDetected = pdTRUE;
	}

	/* Just so we know the test is still running. */
	ulLoopCounter++;

	/* Now we can suspend ourselves so the low priority task can execute
	again. */
	vTaskSuspend( NULL );
	}
	}
	/-----------------------------------------------------------/

	static void prvLowPriorityPeekTask( void *pvParameters )
	{
	QueueHandle_t xQueue = ( QueueHandle_t ) pvParameters;
	uint32_t ulValue;

	for( ;; )
	{
	/* Write some data to the queue. This should unblock the highest
	priority task that is waiting to peek data from the queue. */
	ulValue = 0x11223344;
	if( xQueueSendToBack( xQueue, &ulValue, qpeekNO_BLOCK ) != pdPASS )
	{
	/* We were expecting the queue to be empty so we should not of
	had a problem writing to the queue. */
	xErrorDetected = pdTRUE;
	}

	#if configUSE_PREEMPTION == 0
	taskYIELD();
	#endif

	/* By the time we get here the data should have been removed from
	the queue. */
	if( uxQueueMessagesWaiting( xQueue ) != 0 )
	{
	xErrorDetected = pdTRUE;
	}

	/* Write another value to the queue, again waking the highest priority
	task that is blocked on the queue. */
	ulValue = 0x01234567;
	if( xQueueSendToBack( xQueue, &ulValue, qpeekNO_BLOCK ) != pdPASS )
	{
	/* We were expecting the queue to be empty so we should not of
	had a problem writing to the queue. */
	xErrorDetected = pdTRUE;
	}

	#if configUSE_PREEMPTION == 0
	taskYIELD();
	#endif

	/* All the other tasks should now have successfully peeked the data.
	The data is still in the queue so we should be able to receive it. */
	ulValue = 0;
	if( xQueueReceive( xQueue, &ulValue, qpeekNO_BLOCK ) != pdPASS )
	{
	/* We expected to receive the data. */
	xErrorDetected = pdTRUE;
	}

	if( ulValue != 0x01234567 )
	{
	/* We did not receive the expected value. */
	}

	/* Lets just delay a while as this is an intensive test as we don't
	want to starve other tests of processing time. */
	vTaskDelay( qpeekSHORT_DELAY );

	/* Unsuspend the other tasks so we can repeat the test - this time
	however not all the other tasks will peek the data as the high
	priority task is actually going to remove it from the queue. Send
	to front is used just to be different. As the queue is empty it
	makes no difference to the result. */
	vTaskResume( xMediumPriorityTask );
	vTaskResume( xHighPriorityTask );
	vTaskResume( xHighestPriorityTask );

	#if( configUSE_PREEMPTION == 0 )
	taskYIELD();
	#endif

	ulValue = 0xaabbaabb;
	if( xQueueSendToFront( xQueue, &ulValue, qpeekNO_BLOCK ) != pdPASS )
	{
	/* We were expecting the queue to be empty so we should not of
	had a problem writing to the queue. */
	xErrorDetected = pdTRUE;
	}

	#if configUSE_PREEMPTION == 0
	taskYIELD();
	#endif

	/* This time we should find that the queue is empty. The high priority
	task actually removed the data rather than just peeking it. */
	if( xQueuePeek( xQueue, &ulValue, qpeekNO_BLOCK ) != errQUEUE_EMPTY )
	{
	/* We expected to receive the data. */
	xErrorDetected = pdTRUE;
	}

	/* Unsuspend the highest and high priority tasks so we can go back
	and repeat the whole thing. The medium priority task should not be
	suspended as it was not able to peek the data in this last case. */
	vTaskResume( xHighPriorityTask );
	vTaskResume( xHighestPriorityTask );

	/* Lets just delay a while as this is an intensive test as we don't
	want to starve other tests of processing time. */
	vTaskDelay( qpeekSHORT_DELAY );
	}
	}
	/-----------------------------------------------------------/

	/* This is called to check that all the created tasks are still running. */
	BaseType_t xAreQueuePeekTasksStillRunning( void )
	{
	static uint32_t ulLastLoopCounter = 0;

	/* If the demo task is still running then we expect the loopcounter to
	have incremented since this function was last called. */
	if( ulLastLoopCounter == ulLoopCounter )
	{
	xErrorDetected = pdTRUE;
	}

	ulLastLoopCounter = ulLoopCounter;

	/* Errors detected in the task itself will have latched xErrorDetected
	to true. */

	return ( BaseType_t ) !xErrorDetected;
	}