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/*
* FreeRTOS Kernel <DEVELOPMENT BRANCH>
* Copyright (C) 2021 Amazon.com, Inc. or its affiliates. All Rights Reserved.
*
* SPDX-License-Identifier: MIT
*
* 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.
*
* https://www.FreeRTOS.org
* https://github.com/FreeRTOS
*
*/
/*
* This is the list implementation used by the scheduler. While it is tailored
* heavily for the schedulers needs, it is also available for use by
* application code.
*
* list_ts can only store pointers to list_item_ts. Each ListItem_t contains a
* numeric value (xItemValue). Most of the time the lists are sorted in
* ascending item value order.
*
* Lists are created already containing one list item. The value of this
* item is the maximum possible that can be stored, it is therefore always at
* the end of the list and acts as a marker. The list member pxHead always
* points to this marker - even though it is at the tail of the list. This
* is because the tail contains a wrap back pointer to the true head of
* the list.
*
* In addition to it's value, each list item contains a pointer to the next
* item in the list (pxNext), a pointer to the list it is in (pxContainer)
* and a pointer to back to the object that contains it. These later two
* pointers are included for efficiency of list manipulation. There is
* effectively a two way link between the object containing the list item and
* the list item itself.
*
*
* \page ListIntroduction List Implementation
* \ingroup FreeRTOSIntro
*/
#ifndef LIST_H
#define LIST_H
#ifndef INC_FREERTOS_H
#error "FreeRTOS.h must be included before list.h"
#endif
/*
* The list structure members are modified from within interrupts, and therefore
* by rights should be declared volatile. However, they are only modified in a
* functionally atomic way (within critical sections of with the scheduler
* suspended) and are either passed by reference into a function or indexed via
* a volatile variable. Therefore, in all use cases tested so far, the volatile
* qualifier can be omitted in order to provide a moderate performance
* improvement without adversely affecting functional behaviour. The assembly
* instructions generated by the IAR, ARM and GCC compilers when the respective
* compiler's options were set for maximum optimisation has been inspected and
* deemed to be as intended. That said, as compiler technology advances, and
* especially if aggressive cross module optimisation is used (a use case that
* has not been exercised to any great extend) then it is feasible that the
* volatile qualifier will be needed for correct optimisation. It is expected
* that a compiler removing essential code because, without the volatile
* qualifier on the list structure members and with aggressive cross module
* optimisation, the compiler deemed the code unnecessary will result in
* complete and obvious failure of the scheduler. If this is ever experienced
* then the volatile qualifier can be inserted in the relevant places within the
* list structures by simply defining configLIST_VOLATILE to volatile in
* FreeRTOSConfig.h (as per the example at the bottom of this comment block).
* If configLIST_VOLATILE is not defined then the preprocessor directives below
* will simply #define configLIST_VOLATILE away completely.
*
* To use volatile list structure members then add the following line to
* FreeRTOSConfig.h (without the quotes):
* "#define configLIST_VOLATILE volatile"
*/
#ifndef configLIST_VOLATILE
#define configLIST_VOLATILE
#endif /* configSUPPORT_CROSS_MODULE_OPTIMISATION */
/* *INDENT-OFF* */
#ifdef __cplusplus
extern "C" {
#endif
/* *INDENT-ON* */
/* Macros that can be used to place known values within the list structures,
* then check that the known values do not get corrupted during the execution of
* the application. These may catch the list data structures being overwritten in
* memory. They will not catch data errors caused by incorrect configuration or
* use of FreeRTOS.*/
#if ( configUSE_LIST_DATA_INTEGRITY_CHECK_BYTES == 0 )
/* Define the macros to do nothing. */
#define listFIRST_LIST_ITEM_INTEGRITY_CHECK_VALUE
#define listSECOND_LIST_ITEM_INTEGRITY_CHECK_VALUE
#define listFIRST_LIST_INTEGRITY_CHECK_VALUE
#define listSECOND_LIST_INTEGRITY_CHECK_VALUE
#define listSET_FIRST_LIST_ITEM_INTEGRITY_CHECK_VALUE( pxItem )
#define listSET_SECOND_LIST_ITEM_INTEGRITY_CHECK_VALUE( pxItem )
#define listSET_LIST_INTEGRITY_CHECK_1_VALUE( pxList )
#define listSET_LIST_INTEGRITY_CHECK_2_VALUE( pxList )
#define listTEST_LIST_ITEM_INTEGRITY( pxItem )
#define listTEST_LIST_INTEGRITY( pxList )
#else /* if ( configUSE_LIST_DATA_INTEGRITY_CHECK_BYTES == 0 ) */
/* Define macros that add new members into the list structures. */
#define listFIRST_LIST_ITEM_INTEGRITY_CHECK_VALUE TickType_t xListItemIntegrityValue1;
#define listSECOND_LIST_ITEM_INTEGRITY_CHECK_VALUE TickType_t xListItemIntegrityValue2;
#define listFIRST_LIST_INTEGRITY_CHECK_VALUE TickType_t xListIntegrityValue1;
#define listSECOND_LIST_INTEGRITY_CHECK_VALUE TickType_t xListIntegrityValue2;
/* Define macros that set the new structure members to known values. */
#define listSET_FIRST_LIST_ITEM_INTEGRITY_CHECK_VALUE( pxItem ) ( pxItem )->xListItemIntegrityValue1 = pdINTEGRITY_CHECK_VALUE
#define listSET_SECOND_LIST_ITEM_INTEGRITY_CHECK_VALUE( pxItem ) ( pxItem )->xListItemIntegrityValue2 = pdINTEGRITY_CHECK_VALUE
#define listSET_LIST_INTEGRITY_CHECK_1_VALUE( pxList ) ( pxList )->xListIntegrityValue1 = pdINTEGRITY_CHECK_VALUE
#define listSET_LIST_INTEGRITY_CHECK_2_VALUE( pxList ) ( pxList )->xListIntegrityValue2 = pdINTEGRITY_CHECK_VALUE
/* Define macros that will assert if one of the structure members does not
* contain its expected value. */
#define listTEST_LIST_ITEM_INTEGRITY( pxItem ) configASSERT( ( ( pxItem )->xListItemIntegrityValue1 == pdINTEGRITY_CHECK_VALUE ) && ( ( pxItem )->xListItemIntegrityValue2 == pdINTEGRITY_CHECK_VALUE ) )
#define listTEST_LIST_INTEGRITY( pxList ) configASSERT( ( ( pxList )->xListIntegrityValue1 == pdINTEGRITY_CHECK_VALUE ) && ( ( pxList )->xListIntegrityValue2 == pdINTEGRITY_CHECK_VALUE ) )
#endif /* configUSE_LIST_DATA_INTEGRITY_CHECK_BYTES */
/*
* Definition of the only type of object that a list can contain.
*/
struct xLIST;
struct xLIST_ITEM
{
listFIRST_LIST_ITEM_INTEGRITY_CHECK_VALUE /*< Set to a known value if configUSE_LIST_DATA_INTEGRITY_CHECK_BYTES is set to 1. */
configLIST_VOLATILE TickType_t xItemValue; /*< The value being listed. In most cases this is used to sort the list in ascending order. */
struct xLIST_ITEM * configLIST_VOLATILE pxNext; /*< Pointer to the next ListItem_t in the list. */
struct xLIST_ITEM * configLIST_VOLATILE pxPrevious; /*< Pointer to the previous ListItem_t in the list. */
void * pvOwner; /*< Pointer to the object (normally a TCB) that contains the list item. There is therefore a two way link between the object containing the list item and the list item itself. */
struct xLIST * configLIST_VOLATILE pxContainer; /*< Pointer to the list in which this list item is placed (if any). */
listSECOND_LIST_ITEM_INTEGRITY_CHECK_VALUE /*< Set to a known value if configUSE_LIST_DATA_INTEGRITY_CHECK_BYTES is set to 1. */
};
typedef struct xLIST_ITEM ListItem_t; /* For some reason lint wants this as two separate definitions. */
struct xMINI_LIST_ITEM
{
listFIRST_LIST_ITEM_INTEGRITY_CHECK_VALUE /*< Set to a known value if configUSE_LIST_DATA_INTEGRITY_CHECK_BYTES is set to 1. */
configLIST_VOLATILE TickType_t xItemValue;
struct xLIST_ITEM * configLIST_VOLATILE pxNext;
struct xLIST_ITEM * configLIST_VOLATILE pxPrevious;
};
typedef struct xMINI_LIST_ITEM MiniListItem_t;
/*
* Definition of the type of queue used by the scheduler.
*/
typedef struct xLIST
{
listFIRST_LIST_INTEGRITY_CHECK_VALUE /*< Set to a known value if configUSE_LIST_DATA_INTEGRITY_CHECK_BYTES is set to 1. */
volatile UBaseType_t uxNumberOfItems;
ListItem_t * configLIST_VOLATILE pxIndex; /*< Used to walk through the list. Points to the last item returned by a call to listGET_OWNER_OF_NEXT_ENTRY (). */
MiniListItem_t xListEnd; /*< List item that contains the maximum possible item value meaning it is always at the end of the list and is therefore used as a marker. */
listSECOND_LIST_INTEGRITY_CHECK_VALUE /*< Set to a known value if configUSE_LIST_DATA_INTEGRITY_CHECK_BYTES is set to 1. */
} List_t;
/*
* Access macro to set the owner of a list item. The owner of a list item
* is the object (usually a TCB) that contains the list item.
*
* \page listSET_LIST_ITEM_OWNER listSET_LIST_ITEM_OWNER
* \ingroup LinkedList
*/
#define listSET_LIST_ITEM_OWNER( pxListItem, pxOwner ) ( ( pxListItem )->pvOwner = ( void * ) ( pxOwner ) )
/*
* Access macro to get the owner of a list item. The owner of a list item
* is the object (usually a TCB) that contains the list item.
*
* \page listGET_LIST_ITEM_OWNER listSET_LIST_ITEM_OWNER
* \ingroup LinkedList
*/
#define listGET_LIST_ITEM_OWNER( pxListItem ) ( ( pxListItem )->pvOwner )
/*
* Access macro to set the value of the list item. In most cases the value is
* used to sort the list in ascending order.
*
* \page listSET_LIST_ITEM_VALUE listSET_LIST_ITEM_VALUE
* \ingroup LinkedList
*/
#define listSET_LIST_ITEM_VALUE( pxListItem, xValue ) ( ( pxListItem )->xItemValue = ( xValue ) )
/*
* Access macro to retrieve the value of the list item. The value can
* represent anything - for example the priority of a task, or the time at
* which a task should be unblocked.
*
* \page listGET_LIST_ITEM_VALUE listGET_LIST_ITEM_VALUE
* \ingroup LinkedList
*/
#define listGET_LIST_ITEM_VALUE( pxListItem ) ( ( pxListItem )->xItemValue )
/*
* Access macro to retrieve the value of the list item at the head of a given
* list.
*
* \page listGET_LIST_ITEM_VALUE listGET_LIST_ITEM_VALUE
* \ingroup LinkedList
*/
#define listGET_ITEM_VALUE_OF_HEAD_ENTRY( pxList ) ( ( ( pxList )->xListEnd ).pxNext->xItemValue )
/*
* Return the list item at the head of the list.
*
* \page listGET_HEAD_ENTRY listGET_HEAD_ENTRY
* \ingroup LinkedList
*/
#define listGET_HEAD_ENTRY( pxList ) ( ( ( pxList )->xListEnd ).pxNext )
/*
* Return the next list item.
*
* \page listGET_NEXT listGET_NEXT
* \ingroup LinkedList
*/
#define listGET_NEXT( pxListItem ) ( ( pxListItem )->pxNext )
/*
* Return the list item that marks the end of the list
*
* \page listGET_END_MARKER listGET_END_MARKER
* \ingroup LinkedList
*/
#define listGET_END_MARKER( pxList ) ( ( ListItem_t const * ) ( &( ( pxList )->xListEnd ) ) )
/*
* Access macro to determine if a list contains any items. The macro will
* only have the value true if the list is empty.
*
* \page listLIST_IS_EMPTY listLIST_IS_EMPTY
* \ingroup LinkedList
*/
#define listLIST_IS_EMPTY( pxList ) ( ( ( pxList )->uxNumberOfItems == ( UBaseType_t ) 0 ) ? pdTRUE : pdFALSE )
/*
* Access macro to return the number of items in the list.
*/
#define listCURRENT_LIST_LENGTH( pxList ) ( ( pxList )->uxNumberOfItems )
/*
* Access function to obtain the owner of the next entry in a list.
*
* The list member pxIndex is used to walk through a list. Calling
* listGET_OWNER_OF_NEXT_ENTRY increments pxIndex to the next item in the list
* and returns that entry's pxOwner parameter. Using multiple calls to this
* function it is therefore possible to move through every item contained in
* a list.
*
* The pxOwner parameter of a list item is a pointer to the object that owns
* the list item. In the scheduler this is normally a task control block.
* The pxOwner parameter effectively creates a two way link between the list
* item and its owner.
*
* @param pxTCB pxTCB is set to the address of the owner of the next list item.
* @param pxList The list from which the next item owner is to be returned.
*
* \page listGET_OWNER_OF_NEXT_ENTRY listGET_OWNER_OF_NEXT_ENTRY
* \ingroup LinkedList
*/
#define listGET_OWNER_OF_NEXT_ENTRY( pxTCB, pxList ) \
{ \
List_t * const pxConstList = ( pxList ); \
/* Increment the index to the next item and return the item, ensuring */ \
/* we don't return the marker used at the end of the list. */ \
( pxConstList )->pxIndex = ( pxConstList )->pxIndex->pxNext; \
if( ( void * ) ( pxConstList )->pxIndex == ( void * ) &( ( pxConstList )->xListEnd ) ) \
{ \
( pxConstList )->pxIndex = ( pxConstList )->pxIndex->pxNext; \
} \
( pxTCB ) = ( pxConstList )->pxIndex->pvOwner; \
}
/*
* Version of uxListRemove() that does not return a value. Provided as a slight
* optimisation for xTaskIncrementTick() by being inline.
*
* Remove an item from a list. The list item has a pointer to the list that
* it is in, so only the list item need be passed into the function.
*
* @param uxListRemove The item to be removed. The item will remove itself from
* the list pointed to by it's pxContainer parameter.
*
* @return The number of items that remain in the list after the list item has
* been removed.
*
* \page listREMOVE_ITEM listREMOVE_ITEM
* \ingroup LinkedList
*/
#define listREMOVE_ITEM( pxItemToRemove ) \
{ \
/* The list item knows which list it is in. Obtain the list from the list \
* item. */ \
List_t * const pxList = ( pxItemToRemove )->pxContainer; \
\
( pxItemToRemove )->pxNext->pxPrevious = ( pxItemToRemove )->pxPrevious; \
( pxItemToRemove )->pxPrevious->pxNext = ( pxItemToRemove )->pxNext; \
/* Make sure the index is left pointing to a valid item. */ \
if( pxList->pxIndex == ( pxItemToRemove ) ) \
{ \
pxList->pxIndex = ( pxItemToRemove )->pxPrevious; \
} \
\
( pxItemToRemove )->pxContainer = NULL; \
( pxList->uxNumberOfItems )--; \
}
/*
* Inline version of vListInsertEnd() to provide slight optimisation for
* xTaskIncrementTick().
*
* Insert a list item into a list. The item will be inserted in a position
* such that it will be the last item within the list returned by multiple
* calls to listGET_OWNER_OF_NEXT_ENTRY.
*
* The list member pxIndex is used to walk through a list. Calling
* listGET_OWNER_OF_NEXT_ENTRY increments pxIndex to the next item in the list.
* Placing an item in a list using vListInsertEnd effectively places the item
* in the list position pointed to by pxIndex. This means that every other
* item within the list will be returned by listGET_OWNER_OF_NEXT_ENTRY before
* the pxIndex parameter again points to the item being inserted.
*
* @param pxList The list into which the item is to be inserted.
*
* @param pxNewListItem The list item to be inserted into the list.
*
* \page listINSERT_END listINSERT_END
* \ingroup LinkedList
*/
#define listINSERT_END( pxList, pxNewListItem ) \
{ \
ListItem_t * const pxIndex = ( pxList )->pxIndex; \
\
/* Only effective when configASSERT() is also defined, these tests may catch \
* the list data structures being overwritten in memory. They will not catch \
* data errors caused by incorrect configuration or use of FreeRTOS. */ \
listTEST_LIST_INTEGRITY( ( pxList ) ); \
listTEST_LIST_ITEM_INTEGRITY( ( pxNewListItem ) ); \
\
/* Insert a new list item into ( pxList ), but rather than sort the list, \
* makes the new list item the last item to be removed by a call to \
* listGET_OWNER_OF_NEXT_ENTRY(). */ \
( pxNewListItem )->pxNext = pxIndex; \
( pxNewListItem )->pxPrevious = pxIndex->pxPrevious; \
\
pxIndex->pxPrevious->pxNext = ( pxNewListItem ); \
pxIndex->pxPrevious = ( pxNewListItem ); \
\
/* Remember which list the item is in. */ \
( pxNewListItem )->pxContainer = ( pxList ); \
\
( ( pxList )->uxNumberOfItems )++; \
}
/*
* Access function to obtain the owner of the first entry in a list. Lists
* are normally sorted in ascending item value order.
*
* This function returns the pxOwner member of the first item in the list.
* The pxOwner parameter of a list item is a pointer to the object that owns
* the list item. In the scheduler this is normally a task control block.
* The pxOwner parameter effectively creates a two way link between the list
* item and its owner.
*
* @param pxList The list from which the owner of the head item is to be
* returned.
*
* \page listGET_OWNER_OF_HEAD_ENTRY listGET_OWNER_OF_HEAD_ENTRY
* \ingroup LinkedList
*/
#define listGET_OWNER_OF_HEAD_ENTRY( pxList ) ( ( &( ( pxList )->xListEnd ) )->pxNext->pvOwner )
/*
* Check to see if a list item is within a list. The list item maintains a
* "container" pointer that points to the list it is in. All this macro does
* is check to see if the container and the list match.
*
* @param pxList The list we want to know if the list item is within.
* @param pxListItem The list item we want to know if is in the list.
* @return pdTRUE if the list item is in the list, otherwise pdFALSE.
*/
#define listIS_CONTAINED_WITHIN( pxList, pxListItem ) ( ( ( pxListItem )->pxContainer == ( pxList ) ) ? ( pdTRUE ) : ( pdFALSE ) )
/*
* Return the list a list item is contained within (referenced from).
*
* @param pxListItem The list item being queried.
* @return A pointer to the List_t object that references the pxListItem
*/
#define listLIST_ITEM_CONTAINER( pxListItem ) ( ( pxListItem )->pxContainer )
/*
* This provides a crude means of knowing if a list has been initialised, as
* pxList->xListEnd.xItemValue is set to portMAX_DELAY by the vListInitialise()
* function.
*/
#define listLIST_IS_INITIALISED( pxList ) ( ( pxList )->xListEnd.xItemValue == portMAX_DELAY )
/*
* Must be called before a list is used! This initialises all the members
* of the list structure and inserts the xListEnd item into the list as a
* marker to the back of the list.
*
* @param pxList Pointer to the list being initialised.
*
* \page vListInitialise vListInitialise
* \ingroup LinkedList
*/
void vListInitialise( List_t * const pxList ) PRIVILEGED_FUNCTION;
/*
* Must be called before a list item is used. This sets the list container to
* null so the item does not think that it is already contained in a list.
*
* @param pxItem Pointer to the list item being initialised.
*
* \page vListInitialiseItem vListInitialiseItem
* \ingroup LinkedList
*/
void vListInitialiseItem( ListItem_t * const pxItem ) PRIVILEGED_FUNCTION;
/*
* Insert a list item into a list. The item will be inserted into the list in
* a position determined by its item value (ascending item value order).
*
* @param pxList The list into which the item is to be inserted.
*
* @param pxNewListItem The item that is to be placed in the list.
*
* \page vListInsert vListInsert
* \ingroup LinkedList
*/
void vListInsert( List_t * const pxList,
ListItem_t * const pxNewListItem ) PRIVILEGED_FUNCTION;
/*
* Insert a list item into a list. The item will be inserted in a position
* such that it will be the last item within the list returned by multiple
* calls to listGET_OWNER_OF_NEXT_ENTRY.
*
* The list member pxIndex is used to walk through a list. Calling
* listGET_OWNER_OF_NEXT_ENTRY increments pxIndex to the next item in the list.
* Placing an item in a list using vListInsertEnd effectively places the item
* in the list position pointed to by pxIndex. This means that every other
* item within the list will be returned by listGET_OWNER_OF_NEXT_ENTRY before
* the pxIndex parameter again points to the item being inserted.
*
* @param pxList The list into which the item is to be inserted.
*
* @param pxNewListItem The list item to be inserted into the list.
*
* \page vListInsertEnd vListInsertEnd
* \ingroup LinkedList
*/
void vListInsertEnd( List_t * const pxList,
ListItem_t * const pxNewListItem ) PRIVILEGED_FUNCTION;
/*
* Remove an item from a list. The list item has a pointer to the list that
* it is in, so only the list item need be passed into the function.
*
* @param uxListRemove The item to be removed. The item will remove itself from
* the list pointed to by it's pxContainer parameter.
*
* @return The number of items that remain in the list after the list item has
* been removed.
*
* \page uxListRemove uxListRemove
* \ingroup LinkedList
*/
UBaseType_t uxListRemove( ListItem_t * const pxItemToRemove ) PRIVILEGED_FUNCTION;
/* *INDENT-OFF* */
#ifdef __cplusplus
}
#endif
/* *INDENT-ON* */
#endif /* ifndef LIST_H */