2 #define pr_fmt(fmt) "list_sort_test: " fmt
4 #include <linux/kernel.h>
5 #include <linux/module.h>
6 #include <linux/list_sort.h>
7 #include <linux/slab.h>
8 #include <linux/list.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;
56 /* if equal, take 'a' -- important for sort stability */
57 if ((*cmp)(priv, a, b) <= 0) {
72 * In worst cases this loop may run many iterations.
73 * Continue callbacks to the client even though no
74 * element comparison is needed, so the client's cmp()
75 * routine can invoke cond_resched() periodically.
77 if (unlikely(!(++count)))
78 (*cmp)(priv, tail->next, tail->next);
80 tail->next->prev = tail;
89 * list_sort - sort a list
90 * @priv: private data, opaque to list_sort(), passed to @cmp
91 * @head: the list to sort
92 * @cmp: the elements comparison function
94 * This function implements "merge sort", which has O(nlog(n))
97 * The comparison function @cmp must return a negative value if @a
98 * should sort before @b, and a positive value if @a should sort after
99 * @b. If @a and @b are equivalent, and their original relative
100 * ordering is to be preserved, @cmp must return 0.
102 void list_sort(void *priv, struct list_head *head,
103 int (*cmp)(void *priv, struct list_head *a,
104 struct list_head *b))
106 struct list_head *part[MAX_LIST_LENGTH_BITS+1]; /* sorted partial lists
107 -- last slot is a sentinel */
108 int lev; /* index into part[] */
110 struct list_head *list;
112 if (list_empty(head))
115 memset(part, 0, sizeof(part));
117 head->prev->next = NULL;
121 struct list_head *cur = list;
125 for (lev = 0; part[lev]; lev++) {
126 cur = merge(priv, cmp, part[lev], cur);
130 if (unlikely(lev >= ARRAY_SIZE(part)-1)) {
131 printk_once(KERN_DEBUG "list too long for efficiency\n");
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);
145 EXPORT_SYMBOL(list_sort);
147 #ifdef CONFIG_TEST_LIST_SORT
149 #include <linux/random.h>
152 * The pattern of set bits in the list length determines which cases
153 * are hit in list_sort().
155 #define TEST_LIST_LEN (512+128+2) /* not including head */
157 #define TEST_POISON1 0xDEADBEEF
158 #define TEST_POISON2 0xA324354C
161 unsigned int poison1;
162 struct list_head list;
163 unsigned int poison2;
168 /* Array, containing pointers to all elements in the test list */
169 static struct debug_el **elts __initdata;
171 static int __init check(struct debug_el *ela, struct debug_el *elb)
173 if (ela->serial >= TEST_LIST_LEN) {
174 pr_err("error: incorrect serial %d\n", ela->serial);
177 if (elb->serial >= TEST_LIST_LEN) {
178 pr_err("error: incorrect serial %d\n", elb->serial);
181 if (elts[ela->serial] != ela || elts[elb->serial] != elb) {
182 pr_err("error: phantom element\n");
185 if (ela->poison1 != TEST_POISON1 || ela->poison2 != TEST_POISON2) {
186 pr_err("error: bad poison: %#x/%#x\n",
187 ela->poison1, ela->poison2);
190 if (elb->poison1 != TEST_POISON1 || elb->poison2 != TEST_POISON2) {
191 pr_err("error: bad poison: %#x/%#x\n",
192 elb->poison1, elb->poison2);
198 static int __init cmp(void *priv, struct list_head *a, struct list_head *b)
200 struct debug_el *ela, *elb;
202 ela = container_of(a, struct debug_el, list);
203 elb = container_of(b, struct debug_el, list);
206 return ela->value - elb->value;
209 static int __init list_sort_test(void)
211 int i, count = 1, err = -ENOMEM;
213 struct list_head *cur;
216 pr_debug("start testing list_sort()\n");
218 elts = kcalloc(TEST_LIST_LEN, sizeof(*elts), GFP_KERNEL);
220 pr_err("error: cannot allocate memory\n");
224 for (i = 0; i < TEST_LIST_LEN; i++) {
225 el = kmalloc(sizeof(*el), GFP_KERNEL);
227 pr_err("error: cannot allocate memory\n");
230 /* force some equivalencies */
231 el->value = prandom_u32() % (TEST_LIST_LEN / 3);
233 el->poison1 = TEST_POISON1;
234 el->poison2 = TEST_POISON2;
236 list_add_tail(&el->list, &head);
239 list_sort(NULL, &head, cmp);
242 for (cur = head.next; cur->next != &head; cur = cur->next) {
243 struct debug_el *el1;
246 if (cur->next->prev != cur) {
247 pr_err("error: list is corrupted\n");
251 cmp_result = cmp(NULL, cur, cur->next);
252 if (cmp_result > 0) {
253 pr_err("error: list is not sorted\n");
257 el = container_of(cur, struct debug_el, list);
258 el1 = container_of(cur->next, struct debug_el, list);
259 if (cmp_result == 0 && el->serial >= el1->serial) {
260 pr_err("error: order of equivalent elements not "
265 if (check(el, el1)) {
266 pr_err("error: element check failed\n");
271 if (head.prev != cur) {
272 pr_err("error: list is corrupted\n");
277 if (count != TEST_LIST_LEN) {
278 pr_err("error: bad list length %d", count);
284 for (i = 0; i < TEST_LIST_LEN; i++)
289 module_init(list_sort_test);
290 #endif /* CONFIG_TEST_LIST_SORT */