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git.ipfire.org Git - people/ms/u-boot.git/blob - lib/list_sort.c
2 #include <linux/kernel.h>
3 #include <linux/module.h>
4 #include <linux/slab.h>
6 #include <linux/compat.h>
10 #include <linux/list.h>
11 #include <linux/list_sort.h>
13 #define MAX_LIST_LENGTH_BITS 20
16 * Returns a list organized in an intermediate format suited
17 * to chaining of merge() calls: null-terminated, no reserved or
18 * sentinel head node, "prev" links not maintained.
20 static struct list_head
*merge(void *priv
,
21 int (*cmp
)(void *priv
, struct list_head
*a
,
23 struct list_head
*a
, struct list_head
*b
)
25 struct list_head head
, *tail
= &head
;
28 /* if equal, take 'a' -- important for sort stability */
29 if ((*cmp
)(priv
, a
, b
) <= 0) {
43 * Combine final list merge with restoration of standard doubly-linked
44 * list structure. This approach duplicates code from merge(), but
45 * runs faster than the tidier alternatives of either a separate final
46 * prev-link restoration pass, or maintaining the prev links
49 static void merge_and_restore_back_links(void *priv
,
50 int (*cmp
)(void *priv
, struct list_head
*a
,
52 struct list_head
*head
,
53 struct list_head
*a
, struct list_head
*b
)
55 struct list_head
*tail
= head
;
58 /* if equal, take 'a' -- important for sort stability */
59 if ((*cmp
)(priv
, a
, b
) <= 0) {
74 * In worst cases this loop may run many iterations.
75 * Continue callbacks to the client even though no
76 * element comparison is needed, so the client's cmp()
77 * routine can invoke cond_resched() periodically.
79 (*cmp
)(priv
, tail
->next
, tail
->next
);
81 tail
->next
->prev
= tail
;
90 * list_sort - sort a list
91 * @priv: private data, opaque to list_sort(), passed to @cmp
92 * @head: the list to sort
93 * @cmp: the elements comparison function
95 * This function implements "merge sort", which has O(nlog(n))
98 * The comparison function @cmp must return a negative value if @a
99 * should sort before @b, and a positive value if @a should sort after
100 * @b. If @a and @b are equivalent, and their original relative
101 * ordering is to be preserved, @cmp must return 0.
103 void list_sort(void *priv
, struct list_head
*head
,
104 int (*cmp
)(void *priv
, struct list_head
*a
,
105 struct list_head
*b
))
107 struct list_head
*part
[MAX_LIST_LENGTH_BITS
+1]; /* sorted partial lists
108 -- last slot is a sentinel */
109 int lev
; /* index into part[] */
111 struct list_head
*list
;
113 if (list_empty(head
))
116 memset(part
, 0, sizeof(part
));
118 head
->prev
->next
= NULL
;
122 struct list_head
*cur
= list
;
126 for (lev
= 0; part
[lev
]; lev
++) {
127 cur
= merge(priv
, cmp
, part
[lev
], cur
);
131 if (unlikely(lev
>= ARRAY_SIZE(part
)-1)) {
132 printk_once(KERN_DEBUG
"list passed to"
133 " list_sort() too long for"
142 for (lev
= 0; lev
< max_lev
; lev
++)
144 list
= merge(priv
, cmp
, part
[lev
], list
);
146 merge_and_restore_back_links(priv
, cmp
, head
, part
[max_lev
], list
);
148 EXPORT_SYMBOL(list_sort
);
150 #ifdef CONFIG_TEST_LIST_SORT
152 #include <linux/random.h>
155 * The pattern of set bits in the list length determines which cases
156 * are hit in list_sort().
158 #define TEST_LIST_LEN (512+128+2) /* not including head */
160 #define TEST_POISON1 0xDEADBEEF
161 #define TEST_POISON2 0xA324354C
164 unsigned int poison1
;
165 struct list_head list
;
166 unsigned int poison2
;
171 /* Array, containing pointers to all elements in the test list */
172 static struct debug_el
**elts __initdata
;
174 static int __init
check(struct debug_el
*ela
, struct debug_el
*elb
)
176 if (ela
->serial
>= TEST_LIST_LEN
) {
177 printk(KERN_ERR
"list_sort_test: error: incorrect serial %d\n",
181 if (elb
->serial
>= TEST_LIST_LEN
) {
182 printk(KERN_ERR
"list_sort_test: error: incorrect serial %d\n",
186 if (elts
[ela
->serial
] != ela
|| elts
[elb
->serial
] != elb
) {
187 printk(KERN_ERR
"list_sort_test: error: phantom element\n");
190 if (ela
->poison1
!= TEST_POISON1
|| ela
->poison2
!= TEST_POISON2
) {
191 printk(KERN_ERR
"list_sort_test: error: bad poison: %#x/%#x\n",
192 ela
->poison1
, ela
->poison2
);
195 if (elb
->poison1
!= TEST_POISON1
|| elb
->poison2
!= TEST_POISON2
) {
196 printk(KERN_ERR
"list_sort_test: error: bad poison: %#x/%#x\n",
197 elb
->poison1
, elb
->poison2
);
203 static int __init
cmp(void *priv
, struct list_head
*a
, struct list_head
*b
)
205 struct debug_el
*ela
, *elb
;
207 ela
= container_of(a
, struct debug_el
, list
);
208 elb
= container_of(b
, struct debug_el
, list
);
211 return ela
->value
- elb
->value
;
214 static int __init
list_sort_test(void)
216 int i
, count
= 1, err
= -EINVAL
;
218 struct list_head
*cur
, *tmp
;
221 printk(KERN_DEBUG
"list_sort_test: start testing list_sort()\n");
223 elts
= kmalloc(sizeof(void *) * TEST_LIST_LEN
, GFP_KERNEL
);
225 printk(KERN_ERR
"list_sort_test: error: cannot allocate "
230 for (i
= 0; i
< TEST_LIST_LEN
; i
++) {
231 el
= kmalloc(sizeof(*el
), GFP_KERNEL
);
233 printk(KERN_ERR
"list_sort_test: error: cannot "
234 "allocate memory\n");
237 /* force some equivalencies */
238 el
->value
= prandom_u32() % (TEST_LIST_LEN
/ 3);
240 el
->poison1
= TEST_POISON1
;
241 el
->poison2
= TEST_POISON2
;
243 list_add_tail(&el
->list
, &head
);
246 list_sort(NULL
, &head
, cmp
);
248 for (cur
= head
.next
; cur
->next
!= &head
; cur
= cur
->next
) {
249 struct debug_el
*el1
;
252 if (cur
->next
->prev
!= cur
) {
253 printk(KERN_ERR
"list_sort_test: error: list is "
258 cmp_result
= cmp(NULL
, cur
, cur
->next
);
259 if (cmp_result
> 0) {
260 printk(KERN_ERR
"list_sort_test: error: list is not "
265 el
= container_of(cur
, struct debug_el
, list
);
266 el1
= container_of(cur
->next
, struct debug_el
, list
);
267 if (cmp_result
== 0 && el
->serial
>= el1
->serial
) {
268 printk(KERN_ERR
"list_sort_test: error: order of "
269 "equivalent elements not preserved\n");
273 if (check(el
, el1
)) {
274 printk(KERN_ERR
"list_sort_test: error: element check "
281 if (count
!= TEST_LIST_LEN
) {
282 printk(KERN_ERR
"list_sort_test: error: bad list length %d",
290 list_for_each_safe(cur
, tmp
, &head
) {
292 kfree(container_of(cur
, struct debug_el
, list
));
296 module_init(list_sort_test
);
297 #endif /* CONFIG_TEST_LIST_SORT */