2 #define pr_fmt(fmt) "list_sort_test: " fmt
4 #include <linux/kernel.h>
6 #include <linux/compiler.h>
7 #include <linux/export.h>
8 #include <linux/string.h>
9 #include <linux/list_sort.h>
10 #include <linux/list.h>
12 #define MAX_LIST_LENGTH_BITS 20
15 * Returns a list organized in an intermediate format suited
16 * to chaining of merge() calls: null-terminated, no reserved or
17 * sentinel head node, "prev" links not maintained.
19 static struct list_head
*merge(void *priv
,
20 int (*cmp
)(void *priv
, struct list_head
*a
,
22 struct list_head
*a
, struct list_head
*b
)
24 struct list_head head
, *tail
= &head
;
27 /* if equal, take 'a' -- important for sort stability */
28 if ((*cmp
)(priv
, a
, b
) <= 0) {
42 * Combine final list merge with restoration of standard doubly-linked
43 * list structure. This approach duplicates code from merge(), but
44 * runs faster than the tidier alternatives of either a separate final
45 * prev-link restoration pass, or maintaining the prev links
48 static void merge_and_restore_back_links(void *priv
,
49 int (*cmp
)(void *priv
, struct list_head
*a
,
51 struct list_head
*head
,
52 struct list_head
*a
, struct list_head
*b
)
54 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 if (unlikely(!(++count
)))
80 (*cmp
)(priv
, tail
->next
, tail
->next
);
82 tail
->next
->prev
= tail
;
91 * list_sort - sort a list
92 * @priv: private data, opaque to list_sort(), passed to @cmp
93 * @head: the list to sort
94 * @cmp: the elements comparison function
96 * This function implements "merge sort", which has O(nlog(n))
99 * The comparison function @cmp must return a negative value if @a
100 * should sort before @b, and a positive value if @a should sort after
101 * @b. If @a and @b are equivalent, and their original relative
102 * ordering is to be preserved, @cmp must return 0.
104 void list_sort(void *priv
, struct list_head
*head
,
105 int (*cmp
)(void *priv
, struct list_head
*a
,
106 struct list_head
*b
))
108 struct list_head
*part
[MAX_LIST_LENGTH_BITS
+1]; /* sorted partial lists
109 -- last slot is a sentinel */
110 int lev
; /* index into part[] */
112 struct list_head
*list
;
114 if (list_empty(head
))
117 memset(part
, 0, sizeof(part
));
119 head
->prev
->next
= NULL
;
123 struct list_head
*cur
= list
;
127 for (lev
= 0; part
[lev
]; lev
++) {
128 cur
= merge(priv
, cmp
, part
[lev
], cur
);
132 if (unlikely(lev
>= ARRAY_SIZE(part
)-1)) {
133 printk_once(KERN_DEBUG
"list too long for efficiency\n");
141 for (lev
= 0; lev
< max_lev
; lev
++)
143 list
= merge(priv
, cmp
, part
[lev
], list
);
145 merge_and_restore_back_links(priv
, cmp
, head
, part
[max_lev
], list
);
147 EXPORT_SYMBOL(list_sort
);
149 #ifdef CONFIG_TEST_LIST_SORT
151 #include <linux/slab.h>
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 pr_err("error: incorrect serial %d\n", ela
->serial
);
180 if (elb
->serial
>= TEST_LIST_LEN
) {
181 pr_err("error: incorrect serial %d\n", elb
->serial
);
184 if (elts
[ela
->serial
] != ela
|| elts
[elb
->serial
] != elb
) {
185 pr_err("error: phantom element\n");
188 if (ela
->poison1
!= TEST_POISON1
|| ela
->poison2
!= TEST_POISON2
) {
189 pr_err("error: bad poison: %#x/%#x\n",
190 ela
->poison1
, ela
->poison2
);
193 if (elb
->poison1
!= TEST_POISON1
|| elb
->poison2
!= TEST_POISON2
) {
194 pr_err("error: bad poison: %#x/%#x\n",
195 elb
->poison1
, elb
->poison2
);
201 static int __init
cmp(void *priv
, struct list_head
*a
, struct list_head
*b
)
203 struct debug_el
*ela
, *elb
;
205 ela
= container_of(a
, struct debug_el
, list
);
206 elb
= container_of(b
, struct debug_el
, list
);
209 return ela
->value
- elb
->value
;
212 static int __init
list_sort_test(void)
214 int i
, count
= 1, err
= -ENOMEM
;
216 struct list_head
*cur
;
219 pr_debug("start testing list_sort()\n");
221 elts
= kcalloc(TEST_LIST_LEN
, sizeof(*elts
), GFP_KERNEL
);
223 pr_err("error: cannot allocate memory\n");
227 for (i
= 0; i
< TEST_LIST_LEN
; i
++) {
228 el
= kmalloc(sizeof(*el
), GFP_KERNEL
);
230 pr_err("error: cannot allocate memory\n");
233 /* force some equivalencies */
234 el
->value
= prandom_u32() % (TEST_LIST_LEN
/ 3);
236 el
->poison1
= TEST_POISON1
;
237 el
->poison2
= TEST_POISON2
;
239 list_add_tail(&el
->list
, &head
);
242 list_sort(NULL
, &head
, cmp
);
245 for (cur
= head
.next
; cur
->next
!= &head
; cur
= cur
->next
) {
246 struct debug_el
*el1
;
249 if (cur
->next
->prev
!= cur
) {
250 pr_err("error: list is corrupted\n");
254 cmp_result
= cmp(NULL
, cur
, cur
->next
);
255 if (cmp_result
> 0) {
256 pr_err("error: list is not sorted\n");
260 el
= container_of(cur
, struct debug_el
, list
);
261 el1
= container_of(cur
->next
, struct debug_el
, list
);
262 if (cmp_result
== 0 && el
->serial
>= el1
->serial
) {
263 pr_err("error: order of equivalent elements not "
268 if (check(el
, el1
)) {
269 pr_err("error: element check failed\n");
274 if (head
.prev
!= cur
) {
275 pr_err("error: list is corrupted\n");
280 if (count
!= TEST_LIST_LEN
) {
281 pr_err("error: bad list length %d", count
);
287 for (i
= 0; i
< TEST_LIST_LEN
; i
++)
292 module_init(list_sort_test
);
293 #endif /* CONFIG_TEST_LIST_SORT */
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