Permalink
294 lines (252 sloc) 6.82 KB
#define pr_fmt(fmt) "list_sort_test: " fmt
#include <linux/kernel.h>
#include <linux/bug.h>
#include <linux/compiler.h>
#include <linux/export.h>
#include <linux/string.h>
#include <linux/list_sort.h>
#include <linux/list.h>
#define MAX_LIST_LENGTH_BITS 20
/*
* Returns a list organized in an intermediate format suited
* to chaining of merge() calls: null-terminated, no reserved or
* sentinel head node, "prev" links not maintained.
*/
static struct list_head *merge(void *priv,
int (*cmp)(void *priv, struct list_head *a,
struct list_head *b),
struct list_head *a, struct list_head *b)
{
struct list_head head, *tail = &head;
while (a && b) {
/* if equal, take 'a' -- important for sort stability */
if ((*cmp)(priv, a, b) <= 0) {
tail->next = a;
a = a->next;
} else {
tail->next = b;
b = b->next;
}
tail = tail->next;
}
tail->next = a?:b;
return head.next;
}
/*
* Combine final list merge with restoration of standard doubly-linked
* list structure. This approach duplicates code from merge(), but
* runs faster than the tidier alternatives of either a separate final
* prev-link restoration pass, or maintaining the prev links
* throughout.
*/
static void merge_and_restore_back_links(void *priv,
int (*cmp)(void *priv, struct list_head *a,
struct list_head *b),
struct list_head *head,
struct list_head *a, struct list_head *b)
{
struct list_head *tail = head;
u8 count = 0;
while (a && b) {
/* if equal, take 'a' -- important for sort stability */
if ((*cmp)(priv, a, b) <= 0) {
tail->next = a;
a->prev = tail;
a = a->next;
} else {
tail->next = b;
b->prev = tail;
b = b->next;
}
tail = tail->next;
}
tail->next = a ? : b;
do {
/*
* In worst cases this loop may run many iterations.
* Continue callbacks to the client even though no
* element comparison is needed, so the client's cmp()
* routine can invoke cond_resched() periodically.
*/
if (unlikely(!(++count)))
(*cmp)(priv, tail->next, tail->next);
tail->next->prev = tail;
tail = tail->next;
} while (tail->next);
tail->next = head;
head->prev = tail;
}
/**
* list_sort - sort a list
* @priv: private data, opaque to list_sort(), passed to @cmp
* @head: the list to sort
* @cmp: the elements comparison function
*
* This function implements "merge sort", which has O(nlog(n))
* complexity.
*
* The comparison function @cmp must return a negative value if @a
* should sort before @b, and a positive value if @a should sort after
* @b. If @a and @b are equivalent, and their original relative
* ordering is to be preserved, @cmp must return 0.
*/
void list_sort(void *priv, struct list_head *head,
int (*cmp)(void *priv, struct list_head *a,
struct list_head *b))
{
struct list_head *part[MAX_LIST_LENGTH_BITS+1]; /* sorted partial lists
-- last slot is a sentinel */
int lev; /* index into part[] */
int max_lev = 0;
struct list_head *list;
if (list_empty(head))
return;
memset(part, 0, sizeof(part));
head->prev->next = NULL;
list = head->next;
while (list) {
struct list_head *cur = list;
list = list->next;
cur->next = NULL;
for (lev = 0; part[lev]; lev++) {
cur = merge(priv, cmp, part[lev], cur);
part[lev] = NULL;
}
if (lev > max_lev) {
if (unlikely(lev >= ARRAY_SIZE(part)-1)) {
printk_once(KERN_DEBUG "list too long for efficiency\n");
lev--;
}
max_lev = lev;
}
part[lev] = cur;
}
for (lev = 0; lev < max_lev; lev++)
if (part[lev])
list = merge(priv, cmp, part[lev], list);
merge_and_restore_back_links(priv, cmp, head, part[max_lev], list);
}
EXPORT_SYMBOL(list_sort);
#ifdef CONFIG_TEST_LIST_SORT
#include <linux/slab.h>
#include <linux/random.h>
/*
* The pattern of set bits in the list length determines which cases
* are hit in list_sort().
*/
#define TEST_LIST_LEN (512+128+2) /* not including head */
#define TEST_POISON1 0xDEADBEEF
#define TEST_POISON2 0xA324354C
struct debug_el {
unsigned int poison1;
struct list_head list;
unsigned int poison2;
int value;
unsigned serial;
};
/* Array, containing pointers to all elements in the test list */
static struct debug_el **elts __initdata;
static int __init check(struct debug_el *ela, struct debug_el *elb)
{
if (ela->serial >= TEST_LIST_LEN) {
pr_err("error: incorrect serial %d\n", ela->serial);
return -EINVAL;
}
if (elb->serial >= TEST_LIST_LEN) {
pr_err("error: incorrect serial %d\n", elb->serial);
return -EINVAL;
}
if (elts[ela->serial] != ela || elts[elb->serial] != elb) {
pr_err("error: phantom element\n");
return -EINVAL;
}
if (ela->poison1 != TEST_POISON1 || ela->poison2 != TEST_POISON2) {
pr_err("error: bad poison: %#x/%#x\n",
ela->poison1, ela->poison2);
return -EINVAL;
}
if (elb->poison1 != TEST_POISON1 || elb->poison2 != TEST_POISON2) {
pr_err("error: bad poison: %#x/%#x\n",
elb->poison1, elb->poison2);
return -EINVAL;
}
return 0;
}
static int __init cmp(void *priv, struct list_head *a, struct list_head *b)
{
struct debug_el *ela, *elb;
ela = container_of(a, struct debug_el, list);
elb = container_of(b, struct debug_el, list);
check(ela, elb);
return ela->value - elb->value;
}
static int __init list_sort_test(void)
{
int i, count = 1, err = -ENOMEM;
struct debug_el *el;
struct list_head *cur;
LIST_HEAD(head);
pr_debug("start testing list_sort()\n");
elts = kcalloc(TEST_LIST_LEN, sizeof(*elts), GFP_KERNEL);
if (!elts) {
pr_err("error: cannot allocate memory\n");
return err;
}
for (i = 0; i < TEST_LIST_LEN; i++) {
el = kmalloc(sizeof(*el), GFP_KERNEL);
if (!el) {
pr_err("error: cannot allocate memory\n");
goto exit;
}
/* force some equivalencies */
el->value = prandom_u32() % (TEST_LIST_LEN / 3);
el->serial = i;
el->poison1 = TEST_POISON1;
el->poison2 = TEST_POISON2;
elts[i] = el;
list_add_tail(&el->list, &head);
}
list_sort(NULL, &head, cmp);
err = -EINVAL;
for (cur = head.next; cur->next != &head; cur = cur->next) {
struct debug_el *el1;
int cmp_result;
if (cur->next->prev != cur) {
pr_err("error: list is corrupted\n");
goto exit;
}
cmp_result = cmp(NULL, cur, cur->next);
if (cmp_result > 0) {
pr_err("error: list is not sorted\n");
goto exit;
}
el = container_of(cur, struct debug_el, list);
el1 = container_of(cur->next, struct debug_el, list);
if (cmp_result == 0 && el->serial >= el1->serial) {
pr_err("error: order of equivalent elements not "
"preserved\n");
goto exit;
}
if (check(el, el1)) {
pr_err("error: element check failed\n");
goto exit;
}
count++;
}
if (head.prev != cur) {
pr_err("error: list is corrupted\n");
goto exit;
}
if (count != TEST_LIST_LEN) {
pr_err("error: bad list length %d", count);
goto exit;
}
err = 0;
exit:
for (i = 0; i < TEST_LIST_LEN; i++)
kfree(elts[i]);
kfree(elts);
return err;
}
late_initcall(list_sort_test);
#endif /* CONFIG_TEST_LIST_SORT */