2 * taken from linux kernel lib/list_sort.c, removed uneeded code and adapted
6 #include "kerncompat.h"
10 #define MAX_LIST_LENGTH_BITS 20
13 * Returns a list organized in an intermediate format suited
14 * to chaining of merge() calls: null-terminated, no reserved or
15 * sentinel head node, "prev" links not maintained.
17 static struct list_head *merge(void *priv,
18 int (*cmp)(void *priv, struct list_head *a,
20 struct list_head *a, struct list_head *b)
22 struct list_head head, *tail = &head;
25 /* if equal, take 'a' -- important for sort stability */
26 if ((*cmp)(priv, a, b) <= 0) {
40 * Combine final list merge with restoration of standard doubly-linked
41 * list structure. This approach duplicates code from merge(), but
42 * runs faster than the tidier alternatives of either a separate final
43 * prev-link restoration pass, or maintaining the prev links
46 static void merge_and_restore_back_links(void *priv,
47 int (*cmp)(void *priv, struct list_head *a,
49 struct list_head *head,
50 struct list_head *a, struct list_head *b)
52 struct list_head *tail = head;
55 /* if equal, take 'a' -- important for sort stability */
56 if ((*cmp)(priv, a, b) <= 0) {
71 * In worst cases this loop may run many iterations.
72 * Continue callbacks to the client even though no
73 * element comparison is needed, so the client's cmp()
74 * routine can invoke cond_resched() periodically.
76 (*cmp)(priv, tail->next, tail->next);
78 tail->next->prev = tail;
87 * list_sort - sort a list
88 * @priv: private data, opaque to list_sort(), passed to @cmp
89 * @head: the list to sort
90 * @cmp: the elements comparison function
92 * This function implements "merge sort", which has O(nlog(n))
95 * The comparison function @cmp must return a negative value if @a
96 * should sort before @b, and a positive value if @a should sort after
97 * @b. If @a and @b are equivalent, and their original relative
98 * ordering is to be preserved, @cmp must return 0.
100 void list_sort(void *priv, struct list_head *head,
101 int (*cmp)(void *priv, struct list_head *a,
102 struct list_head *b))
104 struct list_head *part[MAX_LIST_LENGTH_BITS+1]; /* sorted partial lists
105 -- last slot is a sentinel */
106 int lev; /* index into part[] */
108 struct list_head *list;
110 if (list_empty(head))
113 memset(part, 0, sizeof(part));
115 head->prev->next = NULL;
119 struct list_head *cur = list;
123 for (lev = 0; part[lev]; lev++) {
124 cur = merge(priv, cmp, part[lev], cur);
128 if (lev >= ARRAY_SIZE(part)-1) {
129 printf("list_sort: list passed to"
130 " list_sort() too long for"
139 for (lev = 0; lev < max_lev; lev++)
141 list = merge(priv, cmp, part[lev], list);
143 merge_and_restore_back_links(priv, cmp, head, part[max_lev], list);