eal/windows: complete queue.h data structures
authorDmitry Kozlyuk <dmitry.kozliuk@gmail.com>
Mon, 15 Jun 2020 00:43:50 +0000 (03:43 +0300)
committerThomas Monjalon <thomas@monjalon.net>
Mon, 15 Jun 2020 17:27:28 +0000 (19:27 +0200)
Limited version imported previously lacks at least SLIST macros.
Import a complete file from FreeBSD, since its license exception is
already approved by Technical Board.

Signed-off-by: Dmitry Kozlyuk <dmitry.kozliuk@gmail.com>
lib/librte_eal/windows/include/sys/queue.h

index a65949a..9756bee 100644 (file)
@@ -8,7 +8,36 @@
 #define        _SYS_QUEUE_H_
 
 /*
- * This file defines tail queues.
+ * This file defines four types of data structures: singly-linked lists,
+ * singly-linked tail queues, lists and tail queues.
+ *
+ * A singly-linked list is headed by a single forward pointer. The elements
+ * are singly linked for minimum space and pointer manipulation overhead at
+ * the expense of O(n) removal for arbitrary elements. New elements can be
+ * added to the list after an existing element or at the head of the list.
+ * Elements being removed from the head of the list should use the explicit
+ * macro for this purpose for optimum efficiency. A singly-linked list may
+ * only be traversed in the forward direction.  Singly-linked lists are ideal
+ * for applications with large datasets and few or no removals or for
+ * implementing a LIFO queue.
+ *
+ * A singly-linked tail queue is headed by a pair of pointers, one to the
+ * head of the list and the other to the tail of the list. The elements are
+ * singly linked for minimum space and pointer manipulation overhead at the
+ * expense of O(n) removal for arbitrary elements. New elements can be added
+ * to the list after an existing element, at the head of the list, or at the
+ * end of the list. Elements being removed from the head of the tail queue
+ * should use the explicit macro for this purpose for optimum efficiency.
+ * A singly-linked tail queue may only be traversed in the forward direction.
+ * Singly-linked tail queues are ideal for applications with large datasets
+ * and few or no removals or for implementing a FIFO queue.
+ *
+ * A list is headed by a single forward pointer (or an array of forward
+ * pointers for a hash table header). The elements are doubly linked
+ * so that an arbitrary element can be removed without a need to
+ * traverse the list. New elements can be added to the list before
+ * or after an existing element or at the head of the list. A list
+ * may be traversed in either direction.
  *
  * A tail queue is headed by a pair of pointers, one to the head of the
  * list and the other to the tail of the list. The elements are doubly
  * after an existing element, at the head of the list, or at the end of
  * the list. A tail queue may be traversed in either direction.
  *
+ * For details on the use of these macros, see the queue(3) manual page.
+ *
  * Below is a summary of implemented functions where:
  *  +  means the macro is available
  *  -  means the macro is not available
  *  s  means the macro is available but is slow (runs in O(n) time)
  *
- *                             TAILQ
- * _HEAD                       +
- * _CLASS_HEAD                 +
- * _HEAD_INITIALIZER           +
- * _ENTRY                      +
- * _CLASS_ENTRY                        +
- * _INIT                       +
- * _EMPTY                      +
- * _FIRST                      +
- * _NEXT                       +
- * _PREV                       +
- * _LAST                       +
- * _LAST_FAST                  +
- * _FOREACH                    +
- * _FOREACH_FROM               +
- * _FOREACH_SAFE               +
- * _FOREACH_FROM_SAFE          +
- * _FOREACH_REVERSE            +
- * _FOREACH_REVERSE_FROM       +
- * _FOREACH_REVERSE_SAFE       +
- * _FOREACH_REVERSE_FROM_SAFE  +
- * _INSERT_HEAD                        +
- * _INSERT_BEFORE              +
- * _INSERT_AFTER               +
- * _INSERT_TAIL                        +
- * _CONCAT                     +
- * _REMOVE_AFTER               -
- * _REMOVE_HEAD                        -
- * _REMOVE                     +
- * _SWAP                       +
+ *                             SLIST   LIST    STAILQ  TAILQ
+ * _HEAD                       +       +       +       +
+ * _CLASS_HEAD                 +       +       +       +
+ * _HEAD_INITIALIZER           +       +       +       +
+ * _ENTRY                      +       +       +       +
+ * _CLASS_ENTRY                        +       +       +       +
+ * _INIT                       +       +       +       +
+ * _EMPTY                      +       +       +       +
+ * _FIRST                      +       +       +       +
+ * _NEXT                       +       +       +       +
+ * _PREV                       -       +       -       +
+ * _LAST                       -       -       +       +
+ * _LAST_FAST                  -       -       -       +
+ * _FOREACH                    +       +       +       +
+ * _FOREACH_FROM               +       +       +       +
+ * _FOREACH_SAFE               +       +       +       +
+ * _FOREACH_FROM_SAFE          +       +       +       +
+ * _FOREACH_REVERSE            -       -       -       +
+ * _FOREACH_REVERSE_FROM       -       -       -       +
+ * _FOREACH_REVERSE_SAFE       -       -       -       +
+ * _FOREACH_REVERSE_FROM_SAFE  -       -       -       +
+ * _INSERT_HEAD                        +       +       +       +
+ * _INSERT_BEFORE              -       +       -       +
+ * _INSERT_AFTER               +       +       +       +
+ * _INSERT_TAIL                        -       -       +       +
+ * _CONCAT                     s       s       +       +
+ * _REMOVE_AFTER               +       -       +       -
+ * _REMOVE_HEAD                        +       -       +       -
+ * _REMOVE                     s       +       s       +
+ * _SWAP                       +       +       +       +
  *
  */
-
-#ifdef __cplusplus
-extern "C" {
+#ifdef QUEUE_MACRO_DEBUG
+#warn Use QUEUE_MACRO_DEBUG_TRACE and/or QUEUE_MACRO_DEBUG_TRASH
+#define        QUEUE_MACRO_DEBUG_TRACE
+#define        QUEUE_MACRO_DEBUG_TRASH
 #endif
 
-/*
- * List definitions.
- */
-#define        LIST_HEAD(name, type)                                           \
-struct name {                                                          \
-       struct type *lh_first;  /* first element */                     \
-}
+#ifdef QUEUE_MACRO_DEBUG_TRACE
+/* Store the last 2 places the queue element or head was altered */
+struct qm_trace {
+       unsigned long    lastline;
+       unsigned long    prevline;
+       const char      *lastfile;
+       const char      *prevfile;
+};
+
+#define        TRACEBUF        struct qm_trace trace;
+#define        TRACEBUF_INITIALIZER    { __LINE__, 0, __FILE__, NULL } ,
+
+#define        QMD_TRACE_HEAD(head) do {                                       \
+       (head)->trace.prevline = (head)->trace.lastline;                \
+       (head)->trace.prevfile = (head)->trace.lastfile;                \
+       (head)->trace.lastline = __LINE__;                              \
+       (head)->trace.lastfile = __FILE__;                              \
+} while (0)
 
+#define        QMD_TRACE_ELEM(elem) do {                                       \
+       (elem)->trace.prevline = (elem)->trace.lastline;                \
+       (elem)->trace.prevfile = (elem)->trace.lastfile;                \
+       (elem)->trace.lastline = __LINE__;                              \
+       (elem)->trace.lastfile = __FILE__;                              \
+} while (0)
+
+#else  /* !QUEUE_MACRO_DEBUG_TRACE */
 #define        QMD_TRACE_ELEM(elem)
 #define        QMD_TRACE_HEAD(head)
 #define        TRACEBUF
 #define        TRACEBUF_INITIALIZER
+#endif /* QUEUE_MACRO_DEBUG_TRACE */
 
+#ifdef QUEUE_MACRO_DEBUG_TRASH
+#define        QMD_SAVELINK(name, link)        void **name = (void *)&(link)
+#define        TRASHIT(x)              do {(x) = (void *)-1;} while (0)
+#define        QMD_IS_TRASHED(x)       ((x) == (void *)(intptr_t)-1)
+#else  /* !QUEUE_MACRO_DEBUG_TRASH */
+#define        QMD_SAVELINK(name, link)
 #define        TRASHIT(x)
 #define        QMD_IS_TRASHED(x)       0
-
-#define        QMD_SAVELINK(name, link)
+#endif /* QUEUE_MACRO_DEBUG_TRASH */
 
 #ifdef __cplusplus
 /*
@@ -86,6 +143,445 @@ struct name {                                                              \
 #define        QUEUE_TYPEOF(type) struct type
 #endif
 
+/*
+ * Singly-linked List declarations.
+ */
+#define        SLIST_HEAD(name, type)                                          \
+struct name {                                                          \
+       struct type *slh_first; /* first element */                     \
+}
+
+#define        SLIST_CLASS_HEAD(name, type)                                    \
+struct name {                                                          \
+       class type *slh_first;  /* first element */                     \
+}
+
+#define        SLIST_HEAD_INITIALIZER(head)                                    \
+       { NULL }
+
+#define        SLIST_ENTRY(type)                                               \
+struct {                                                               \
+       struct type *sle_next;  /* next element */                      \
+}
+
+#define        SLIST_CLASS_ENTRY(type)                                         \
+struct {                                                               \
+       class type *sle_next;           /* next element */              \
+}
+
+/*
+ * Singly-linked List functions.
+ */
+#if (defined(_KERNEL) && defined(INVARIANTS))
+#define        QMD_SLIST_CHECK_PREVPTR(prevp, elm) do {                        \
+       if (*(prevp) != (elm))                                          \
+               panic("Bad prevptr *(%p) == %p != %p",                  \
+                   (prevp), *(prevp), (elm));                          \
+} while (0)
+#else
+#define        QMD_SLIST_CHECK_PREVPTR(prevp, elm)
+#endif
+
+#define SLIST_CONCAT(head1, head2, type, field) do {                   \
+       QUEUE_TYPEOF(type) *curelm = SLIST_FIRST(head1);                \
+       if (curelm == NULL) {                                           \
+               if ((SLIST_FIRST(head1) = SLIST_FIRST(head2)) != NULL)  \
+                       SLIST_INIT(head2);                              \
+       } else if (SLIST_FIRST(head2) != NULL) {                        \
+               while (SLIST_NEXT(curelm, field) != NULL)               \
+                       curelm = SLIST_NEXT(curelm, field);             \
+               SLIST_NEXT(curelm, field) = SLIST_FIRST(head2);         \
+               SLIST_INIT(head2);                                      \
+       }                                                               \
+} while (0)
+
+#define        SLIST_EMPTY(head)       ((head)->slh_first == NULL)
+
+#define        SLIST_FIRST(head)       ((head)->slh_first)
+
+#define        SLIST_FOREACH(var, head, field)                                 \
+       for ((var) = SLIST_FIRST((head));                               \
+           (var);                                                      \
+           (var) = SLIST_NEXT((var), field))
+
+#define        SLIST_FOREACH_FROM(var, head, field)                            \
+       for ((var) = ((var) ? (var) : SLIST_FIRST((head)));             \
+           (var);                                                      \
+           (var) = SLIST_NEXT((var), field))
+
+#define        SLIST_FOREACH_SAFE(var, head, field, tvar)                      \
+       for ((var) = SLIST_FIRST((head));                               \
+           (var) && ((tvar) = SLIST_NEXT((var), field), 1);            \
+           (var) = (tvar))
+
+#define        SLIST_FOREACH_FROM_SAFE(var, head, field, tvar)                 \
+       for ((var) = ((var) ? (var) : SLIST_FIRST((head)));             \
+           (var) && ((tvar) = SLIST_NEXT((var), field), 1);            \
+           (var) = (tvar))
+
+#define        SLIST_FOREACH_PREVPTR(var, varp, head, field)                   \
+       for ((varp) = &SLIST_FIRST((head));                             \
+           ((var) = *(varp)) != NULL;                                  \
+           (varp) = &SLIST_NEXT((var), field))
+
+#define        SLIST_INIT(head) do {                                           \
+       SLIST_FIRST((head)) = NULL;                                     \
+} while (0)
+
+#define        SLIST_INSERT_AFTER(slistelm, elm, field) do {                   \
+       SLIST_NEXT((elm), field) = SLIST_NEXT((slistelm), field);       \
+       SLIST_NEXT((slistelm), field) = (elm);                          \
+} while (0)
+
+#define        SLIST_INSERT_HEAD(head, elm, field) do {                        \
+       SLIST_NEXT((elm), field) = SLIST_FIRST((head));                 \
+       SLIST_FIRST((head)) = (elm);                                    \
+} while (0)
+
+#define        SLIST_NEXT(elm, field)  ((elm)->field.sle_next)
+
+#define        SLIST_REMOVE(head, elm, type, field) do {                       \
+       QMD_SAVELINK(oldnext, (elm)->field.sle_next);                   \
+       if (SLIST_FIRST((head)) == (elm)) {                             \
+               SLIST_REMOVE_HEAD((head), field);                       \
+       }                                                               \
+       else {                                                          \
+               QUEUE_TYPEOF(type) *curelm = SLIST_FIRST(head);         \
+               while (SLIST_NEXT(curelm, field) != (elm))              \
+                       curelm = SLIST_NEXT(curelm, field);             \
+               SLIST_REMOVE_AFTER(curelm, field);                      \
+       }                                                               \
+       TRASHIT(*oldnext);                                              \
+} while (0)
+
+#define SLIST_REMOVE_AFTER(elm, field) do {                            \
+       SLIST_NEXT(elm, field) =                                        \
+           SLIST_NEXT(SLIST_NEXT(elm, field), field);                  \
+} while (0)
+
+#define        SLIST_REMOVE_HEAD(head, field) do {                             \
+       SLIST_FIRST((head)) = SLIST_NEXT(SLIST_FIRST((head)), field);   \
+} while (0)
+
+#define        SLIST_REMOVE_PREVPTR(prevp, elm, field) do {                    \
+       QMD_SLIST_CHECK_PREVPTR(prevp, elm);                            \
+       *(prevp) = SLIST_NEXT(elm, field);                              \
+       TRASHIT((elm)->field.sle_next);                                 \
+} while (0)
+
+#define SLIST_SWAP(head1, head2, type) do {                            \
+       QUEUE_TYPEOF(type) *swap_first = SLIST_FIRST(head1);            \
+       SLIST_FIRST(head1) = SLIST_FIRST(head2);                        \
+       SLIST_FIRST(head2) = swap_first;                                \
+} while (0)
+
+/*
+ * Singly-linked Tail queue declarations.
+ */
+#define        STAILQ_HEAD(name, type)                                         \
+struct name {                                                          \
+       struct type *stqh_first;/* first element */                     \
+       struct type **stqh_last;/* addr of last next element */         \
+}
+
+#define        STAILQ_CLASS_HEAD(name, type)                                   \
+struct name {                                                          \
+       class type *stqh_first; /* first element */                     \
+       class type **stqh_last; /* addr of last next element */         \
+}
+
+#define        STAILQ_HEAD_INITIALIZER(head)                                   \
+       { NULL, &(head).stqh_first }
+
+#define        STAILQ_ENTRY(type)                                              \
+struct {                                                               \
+       struct type *stqe_next; /* next element */                      \
+}
+
+#define        STAILQ_CLASS_ENTRY(type)                                        \
+struct {                                                               \
+       class type *stqe_next;  /* next element */                      \
+}
+
+/*
+ * Singly-linked Tail queue functions.
+ */
+#define        STAILQ_CONCAT(head1, head2) do {                                \
+       if (!STAILQ_EMPTY((head2))) {                                   \
+               *(head1)->stqh_last = (head2)->stqh_first;              \
+               (head1)->stqh_last = (head2)->stqh_last;                \
+               STAILQ_INIT((head2));                                   \
+       }                                                               \
+} while (0)
+
+#define        STAILQ_EMPTY(head)      ((head)->stqh_first == NULL)
+
+#define        STAILQ_FIRST(head)      ((head)->stqh_first)
+
+#define        STAILQ_FOREACH(var, head, field)                                \
+       for((var) = STAILQ_FIRST((head));                               \
+          (var);                                                       \
+          (var) = STAILQ_NEXT((var), field))
+
+#define        STAILQ_FOREACH_FROM(var, head, field)                           \
+       for ((var) = ((var) ? (var) : STAILQ_FIRST((head)));            \
+          (var);                                                       \
+          (var) = STAILQ_NEXT((var), field))
+
+#define        STAILQ_FOREACH_SAFE(var, head, field, tvar)                     \
+       for ((var) = STAILQ_FIRST((head));                              \
+           (var) && ((tvar) = STAILQ_NEXT((var), field), 1);           \
+           (var) = (tvar))
+
+#define        STAILQ_FOREACH_FROM_SAFE(var, head, field, tvar)                \
+       for ((var) = ((var) ? (var) : STAILQ_FIRST((head)));            \
+           (var) && ((tvar) = STAILQ_NEXT((var), field), 1);           \
+           (var) = (tvar))
+
+#define        STAILQ_INIT(head) do {                                          \
+       STAILQ_FIRST((head)) = NULL;                                    \
+       (head)->stqh_last = &STAILQ_FIRST((head));                      \
+} while (0)
+
+#define        STAILQ_INSERT_AFTER(head, tqelm, elm, field) do {               \
+       if ((STAILQ_NEXT((elm), field) = STAILQ_NEXT((tqelm), field)) == NULL)\
+               (head)->stqh_last = &STAILQ_NEXT((elm), field);         \
+       STAILQ_NEXT((tqelm), field) = (elm);                            \
+} while (0)
+
+#define        STAILQ_INSERT_HEAD(head, elm, field) do {                       \
+       if ((STAILQ_NEXT((elm), field) = STAILQ_FIRST((head))) == NULL) \
+               (head)->stqh_last = &STAILQ_NEXT((elm), field);         \
+       STAILQ_FIRST((head)) = (elm);                                   \
+} while (0)
+
+#define        STAILQ_INSERT_TAIL(head, elm, field) do {                       \
+       STAILQ_NEXT((elm), field) = NULL;                               \
+       *(head)->stqh_last = (elm);                                     \
+       (head)->stqh_last = &STAILQ_NEXT((elm), field);                 \
+} while (0)
+
+#define        STAILQ_LAST(head, type, field)                          \
+       (STAILQ_EMPTY((head)) ? NULL :                          \
+           __containerof((head)->stqh_last,                    \
+           QUEUE_TYPEOF(type), field.stqe_next))
+
+#define        STAILQ_NEXT(elm, field) ((elm)->field.stqe_next)
+
+#define        STAILQ_REMOVE(head, elm, type, field) do {                      \
+       QMD_SAVELINK(oldnext, (elm)->field.stqe_next);                  \
+       if (STAILQ_FIRST((head)) == (elm)) {                            \
+               STAILQ_REMOVE_HEAD((head), field);                      \
+       }                                                               \
+       else {                                                          \
+               QUEUE_TYPEOF(type) *curelm = STAILQ_FIRST(head);        \
+               while (STAILQ_NEXT(curelm, field) != (elm))             \
+                       curelm = STAILQ_NEXT(curelm, field);            \
+               STAILQ_REMOVE_AFTER(head, curelm, field);               \
+       }                                                               \
+       TRASHIT(*oldnext);                                              \
+} while (0)
+
+#define STAILQ_REMOVE_AFTER(head, elm, field) do {                     \
+       if ((STAILQ_NEXT(elm, field) =                                  \
+            STAILQ_NEXT(STAILQ_NEXT(elm, field), field)) == NULL)      \
+               (head)->stqh_last = &STAILQ_NEXT((elm), field);         \
+} while (0)
+
+#define        STAILQ_REMOVE_HEAD(head, field) do {                            \
+       if ((STAILQ_FIRST((head)) =                                     \
+            STAILQ_NEXT(STAILQ_FIRST((head)), field)) == NULL)         \
+               (head)->stqh_last = &STAILQ_FIRST((head));              \
+} while (0)
+
+#define STAILQ_SWAP(head1, head2, type) do {                           \
+       QUEUE_TYPEOF(type) *swap_first = STAILQ_FIRST(head1);           \
+       QUEUE_TYPEOF(type) **swap_last = (head1)->stqh_last;            \
+       STAILQ_FIRST(head1) = STAILQ_FIRST(head2);                      \
+       (head1)->stqh_last = (head2)->stqh_last;                        \
+       STAILQ_FIRST(head2) = swap_first;                               \
+       (head2)->stqh_last = swap_last;                                 \
+       if (STAILQ_EMPTY(head1))                                        \
+               (head1)->stqh_last = &STAILQ_FIRST(head1);              \
+       if (STAILQ_EMPTY(head2))                                        \
+               (head2)->stqh_last = &STAILQ_FIRST(head2);              \
+} while (0)
+
+
+/*
+ * List declarations.
+ */
+#define        LIST_HEAD(name, type)                                           \
+struct name {                                                          \
+       struct type *lh_first;  /* first element */                     \
+}
+
+#define        LIST_CLASS_HEAD(name, type)                                     \
+struct name {                                                          \
+       class type *lh_first;   /* first element */                     \
+}
+
+#define        LIST_HEAD_INITIALIZER(head)                                     \
+       { NULL }
+
+#define        LIST_ENTRY(type)                                                \
+struct {                                                               \
+       struct type *le_next;   /* next element */                      \
+       struct type **le_prev;  /* address of previous next element */  \
+}
+
+#define        LIST_CLASS_ENTRY(type)                                          \
+struct {                                                               \
+       class type *le_next;    /* next element */                      \
+       class type **le_prev;   /* address of previous next element */  \
+}
+
+/*
+ * List functions.
+ */
+
+#if (defined(_KERNEL) && defined(INVARIANTS))
+/*
+ * QMD_LIST_CHECK_HEAD(LIST_HEAD *head, LIST_ENTRY NAME)
+ *
+ * If the list is non-empty, validates that the first element of the list
+ * points back at 'head.'
+ */
+#define        QMD_LIST_CHECK_HEAD(head, field) do {                           \
+       if (LIST_FIRST((head)) != NULL &&                               \
+           LIST_FIRST((head))->field.le_prev !=                        \
+            &LIST_FIRST((head)))                                       \
+               panic("Bad list head %p first->prev != head", (head));  \
+} while (0)
+
+/*
+ * QMD_LIST_CHECK_NEXT(TYPE *elm, LIST_ENTRY NAME)
+ *
+ * If an element follows 'elm' in the list, validates that the next element
+ * points back at 'elm.'
+ */
+#define        QMD_LIST_CHECK_NEXT(elm, field) do {                            \
+       if (LIST_NEXT((elm), field) != NULL &&                          \
+           LIST_NEXT((elm), field)->field.le_prev !=                   \
+            &((elm)->field.le_next))                                   \
+               panic("Bad link elm %p next->prev != elm", (elm));      \
+} while (0)
+
+/*
+ * QMD_LIST_CHECK_PREV(TYPE *elm, LIST_ENTRY NAME)
+ *
+ * Validates that the previous element (or head of the list) points to 'elm.'
+ */
+#define        QMD_LIST_CHECK_PREV(elm, field) do {                            \
+       if (*(elm)->field.le_prev != (elm))                             \
+               panic("Bad link elm %p prev->next != elm", (elm));      \
+} while (0)
+#else
+#define        QMD_LIST_CHECK_HEAD(head, field)
+#define        QMD_LIST_CHECK_NEXT(elm, field)
+#define        QMD_LIST_CHECK_PREV(elm, field)
+#endif /* (_KERNEL && INVARIANTS) */
+
+#define LIST_CONCAT(head1, head2, type, field) do {                          \
+       QUEUE_TYPEOF(type) *curelm = LIST_FIRST(head1);                       \
+       if (curelm == NULL) {                                                 \
+               if ((LIST_FIRST(head1) = LIST_FIRST(head2)) != NULL) {        \
+                       LIST_FIRST(head2)->field.le_prev =                    \
+                           &LIST_FIRST((head1));                             \
+                       LIST_INIT(head2);                                     \
+               }                                                             \
+       } else if (LIST_FIRST(head2) != NULL) {                               \
+               while (LIST_NEXT(curelm, field) != NULL)                      \
+                       curelm = LIST_NEXT(curelm, field);                    \
+               LIST_NEXT(curelm, field) = LIST_FIRST(head2);                 \
+               LIST_FIRST(head2)->field.le_prev = &LIST_NEXT(curelm, field); \
+               LIST_INIT(head2);                                             \
+       }                                                                     \
+} while (0)
+
+#define        LIST_EMPTY(head)        ((head)->lh_first == NULL)
+
+#define        LIST_FIRST(head)        ((head)->lh_first)
+
+#define        LIST_FOREACH(var, head, field)                                  \
+       for ((var) = LIST_FIRST((head));                                \
+           (var);                                                      \
+           (var) = LIST_NEXT((var), field))
+
+#define        LIST_FOREACH_FROM(var, head, field)                             \
+       for ((var) = ((var) ? (var) : LIST_FIRST((head)));              \
+           (var);                                                      \
+           (var) = LIST_NEXT((var), field))
+
+#define        LIST_FOREACH_SAFE(var, head, field, tvar)                       \
+       for ((var) = LIST_FIRST((head));                                \
+           (var) && ((tvar) = LIST_NEXT((var), field), 1);             \
+           (var) = (tvar))
+
+#define        LIST_FOREACH_FROM_SAFE(var, head, field, tvar)                  \
+       for ((var) = ((var) ? (var) : LIST_FIRST((head)));              \
+           (var) && ((tvar) = LIST_NEXT((var), field), 1);             \
+           (var) = (tvar))
+
+#define        LIST_INIT(head) do {                                            \
+       LIST_FIRST((head)) = NULL;                                      \
+} while (0)
+
+#define        LIST_INSERT_AFTER(listelm, elm, field) do {                     \
+       QMD_LIST_CHECK_NEXT(listelm, field);                            \
+       if ((LIST_NEXT((elm), field) = LIST_NEXT((listelm), field)) != NULL)\
+               LIST_NEXT((listelm), field)->field.le_prev =            \
+                   &LIST_NEXT((elm), field);                           \
+       LIST_NEXT((listelm), field) = (elm);                            \
+       (elm)->field.le_prev = &LIST_NEXT((listelm), field);            \
+} while (0)
+
+#define        LIST_INSERT_BEFORE(listelm, elm, field) do {                    \
+       QMD_LIST_CHECK_PREV(listelm, field);                            \
+       (elm)->field.le_prev = (listelm)->field.le_prev;                \
+       LIST_NEXT((elm), field) = (listelm);                            \
+       *(listelm)->field.le_prev = (elm);                              \
+       (listelm)->field.le_prev = &LIST_NEXT((elm), field);            \
+} while (0)
+
+#define        LIST_INSERT_HEAD(head, elm, field) do {                         \
+       QMD_LIST_CHECK_HEAD((head), field);                             \
+       if ((LIST_NEXT((elm), field) = LIST_FIRST((head))) != NULL)     \
+               LIST_FIRST((head))->field.le_prev = &LIST_NEXT((elm), field);\
+       LIST_FIRST((head)) = (elm);                                     \
+       (elm)->field.le_prev = &LIST_FIRST((head));                     \
+} while (0)
+
+#define        LIST_NEXT(elm, field)   ((elm)->field.le_next)
+
+#define        LIST_PREV(elm, head, type, field)                       \
+       ((elm)->field.le_prev == &LIST_FIRST((head)) ? NULL :   \
+           __containerof((elm)->field.le_prev,                 \
+           QUEUE_TYPEOF(type), field.le_next))
+
+#define        LIST_REMOVE(elm, field) do {                                    \
+       QMD_SAVELINK(oldnext, (elm)->field.le_next);                    \
+       QMD_SAVELINK(oldprev, (elm)->field.le_prev);                    \
+       QMD_LIST_CHECK_NEXT(elm, field);                                \
+       QMD_LIST_CHECK_PREV(elm, field);                                \
+       if (LIST_NEXT((elm), field) != NULL)                            \
+               LIST_NEXT((elm), field)->field.le_prev =                \
+                   (elm)->field.le_prev;                               \
+       *(elm)->field.le_prev = LIST_NEXT((elm), field);                \
+       TRASHIT(*oldnext);                                              \
+       TRASHIT(*oldprev);                                              \
+} while (0)
+
+#define LIST_SWAP(head1, head2, type, field) do {                      \
+       QUEUE_TYPEOF(type) *swap_tmp = LIST_FIRST(head1);               \
+       LIST_FIRST((head1)) = LIST_FIRST((head2));                      \
+       LIST_FIRST((head2)) = swap_tmp;                                 \
+       if ((swap_tmp = LIST_FIRST((head1))) != NULL)                   \
+               swap_tmp->field.le_prev = &LIST_FIRST((head1));         \
+       if ((swap_tmp = LIST_FIRST((head2))) != NULL)                   \
+               swap_tmp->field.le_prev = &LIST_FIRST((head2));         \
+} while (0)
+
 /*
  * Tail queue declarations.
  */
@@ -123,10 +619,58 @@ struct {                                                          \
 /*
  * Tail queue functions.
  */
+#if (defined(_KERNEL) && defined(INVARIANTS))
+/*
+ * QMD_TAILQ_CHECK_HEAD(TAILQ_HEAD *head, TAILQ_ENTRY NAME)
+ *
+ * If the tailq is non-empty, validates that the first element of the tailq
+ * points back at 'head.'
+ */
+#define        QMD_TAILQ_CHECK_HEAD(head, field) do {                          \
+       if (!TAILQ_EMPTY(head) &&                                       \
+           TAILQ_FIRST((head))->field.tqe_prev !=                      \
+            &TAILQ_FIRST((head)))                                      \
+               panic("Bad tailq head %p first->prev != head", (head)); \
+} while (0)
+
+/*
+ * QMD_TAILQ_CHECK_TAIL(TAILQ_HEAD *head, TAILQ_ENTRY NAME)
+ *
+ * Validates that the tail of the tailq is a pointer to pointer to NULL.
+ */
+#define        QMD_TAILQ_CHECK_TAIL(head, field) do {                          \
+       if (*(head)->tqh_last != NULL)                                  \
+               panic("Bad tailq NEXT(%p->tqh_last) != NULL", (head));  \
+} while (0)
+
+/*
+ * QMD_TAILQ_CHECK_NEXT(TYPE *elm, TAILQ_ENTRY NAME)
+ *
+ * If an element follows 'elm' in the tailq, validates that the next element
+ * points back at 'elm.'
+ */
+#define        QMD_TAILQ_CHECK_NEXT(elm, field) do {                           \
+       if (TAILQ_NEXT((elm), field) != NULL &&                         \
+           TAILQ_NEXT((elm), field)->field.tqe_prev !=                 \
+            &((elm)->field.tqe_next))                                  \
+               panic("Bad link elm %p next->prev != elm", (elm));      \
+} while (0)
+
+/*
+ * QMD_TAILQ_CHECK_PREV(TYPE *elm, TAILQ_ENTRY NAME)
+ *
+ * Validates that the previous element (or head of the tailq) points to 'elm.'
+ */
+#define        QMD_TAILQ_CHECK_PREV(elm, field) do {                           \
+       if (*(elm)->field.tqe_prev != (elm))                            \
+               panic("Bad link elm %p prev->next != elm", (elm));      \
+} while (0)
+#else
 #define        QMD_TAILQ_CHECK_HEAD(head, field)
 #define        QMD_TAILQ_CHECK_TAIL(head, headname)
 #define        QMD_TAILQ_CHECK_NEXT(elm, field)
 #define        QMD_TAILQ_CHECK_PREV(elm, field)
+#endif /* (_KERNEL && INVARIANTS) */
 
 #define        TAILQ_CONCAT(head1, head2, field) do {                          \
        if (!TAILQ_EMPTY(head2)) {                                      \
@@ -191,9 +735,8 @@ struct {                                                            \
 
 #define        TAILQ_INSERT_AFTER(head, listelm, elm, field) do {              \
        QMD_TAILQ_CHECK_NEXT(listelm, field);                           \
-       TAILQ_NEXT((elm), field) = TAILQ_NEXT((listelm), field);        \
-       if (TAILQ_NEXT((listelm), field) != NULL)                       \
-               TAILQ_NEXT((elm), field)->field.tqe_prev =              \
+       if ((TAILQ_NEXT((elm), field) = TAILQ_NEXT((listelm), field)) != NULL)\
+               TAILQ_NEXT((elm), field)->field.tqe_prev =              \
                    &TAILQ_NEXT((elm), field);                          \
        else {                                                          \
                (head)->tqh_last = &TAILQ_NEXT((elm), field);           \
@@ -217,8 +760,7 @@ struct {                                                            \
 
 #define        TAILQ_INSERT_HEAD(head, elm, field) do {                        \
        QMD_TAILQ_CHECK_HEAD(head, field);                              \
-       TAILQ_NEXT((elm), field) = TAILQ_FIRST((head));                 \
-       if (TAILQ_FIRST((head)) != NULL)                                \
+       if ((TAILQ_NEXT((elm), field) = TAILQ_FIRST((head))) != NULL)   \
                TAILQ_FIRST((head))->field.tqe_prev =                   \
                    &TAILQ_NEXT((elm), field);                          \
        else                                                            \
@@ -250,21 +792,24 @@ struct {                                                          \
  * you may want to prefetch the last data element.
  */
 #define        TAILQ_LAST_FAST(head, type, field)                      \
-       (TAILQ_EMPTY(head) ? NULL : __containerof((head)->tqh_last,     \
-       QUEUE_TYPEOF(type), field.tqe_next))
+    (TAILQ_EMPTY(head) ? NULL : __containerof((head)->tqh_last, QUEUE_TYPEOF(type), field.tqe_next))
 
 #define        TAILQ_NEXT(elm, field) ((elm)->field.tqe_next)
 
 #define        TAILQ_PREV(elm, headname, field)                                \
        (*(((struct headname *)((elm)->field.tqe_prev))->tqh_last))
 
+#define        TAILQ_PREV_FAST(elm, head, type, field)                         \
+    ((elm)->field.tqe_prev == &(head)->tqh_first ? NULL :              \
+     __containerof((elm)->field.tqe_prev, QUEUE_TYPEOF(type), field.tqe_next))
+
 #define        TAILQ_REMOVE(head, elm, field) do {                             \
        QMD_SAVELINK(oldnext, (elm)->field.tqe_next);                   \
        QMD_SAVELINK(oldprev, (elm)->field.tqe_prev);                   \
        QMD_TAILQ_CHECK_NEXT(elm, field);                               \
        QMD_TAILQ_CHECK_PREV(elm, field);                               \
        if ((TAILQ_NEXT((elm), field)) != NULL)                         \
-               TAILQ_NEXT((elm), field)->field.tqe_prev =              \
+               TAILQ_NEXT((elm), field)->field.tqe_prev =              \
                    (elm)->field.tqe_prev;                              \
        else {                                                          \
                (head)->tqh_last = (elm)->field.tqe_prev;               \
@@ -277,26 +822,20 @@ struct {                                                          \
 } while (0)
 
 #define TAILQ_SWAP(head1, head2, type, field) do {                     \
-       QUEUE_TYPEOF(type) * swap_first = (head1)->tqh_first;           \
-       QUEUE_TYPEOF(type) * *swap_last = (head1)->tqh_last;            \
+       QUEUE_TYPEOF(type) *swap_first = (head1)->tqh_first;            \
+       QUEUE_TYPEOF(type) **swap_last = (head1)->tqh_last;             \
        (head1)->tqh_first = (head2)->tqh_first;                        \
        (head1)->tqh_last = (head2)->tqh_last;                          \
        (head2)->tqh_first = swap_first;                                \
        (head2)->tqh_last = swap_last;                                  \
-       swap_first = (head1)->tqh_first;                                \
-       if (swap_first != NULL)                                         \
+       if ((swap_first = (head1)->tqh_first) != NULL)                  \
                swap_first->field.tqe_prev = &(head1)->tqh_first;       \
        else                                                            \
                (head1)->tqh_last = &(head1)->tqh_first;                \
-       swap_first = (head2)->tqh_first;                                \
-       if (swap_first != NULL)                 \
+       if ((swap_first = (head2)->tqh_first) != NULL)                  \
                swap_first->field.tqe_prev = &(head2)->tqh_first;       \
        else                                                            \
                (head2)->tqh_last = &(head2)->tqh_first;                \
 } while (0)
 
-#ifdef __cplusplus
-}
-#endif
-
-#endif /* _SYS_QUEUE_H_ */
+#endif /* !_SYS_QUEUE_H_ */