typedef struct xLIST
{
listFIRST_LIST_INTEGRITY_CHECK_VALUE    /*< Set to a known value if configUSE_LIST_DATA_INTEGRITY_CHECK_BYTES is set to 1. */
configLIST_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;

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#ifndef configLIST_VOLATILE
#define configLIST_VOLATILE
#endif /

configLIST_VOLATILE在这里有什么用，为什么这么定义变量？

VOLATILE 就是Volatile，在config.h自定义实现的，如果没有就是没有吧，我记得好像是这样子的

* To use volatile list structure members then add the following line to
* FreeRTOSConfig.h (without the quotes):
* "#define configLIST_VOLATILE volatile"

list.h里面已经注释很详细了，至于为啥这么定义，查一下volatile的用法就懂了

volatile还是防止编译器做优化