#include <linux/kernel.h>#include <linux/module.h>#include <linux/list_sort.h>#include <linux/slab.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; 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. */ (*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 passed to" " list_sort() 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/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) { printk(KERN_ERR "list_sort_test: error: incorrect serial %d\n", ela->serial); return -EINVAL; } if (elb->serial >= TEST_LIST_LEN) { printk(KERN_ERR "list_sort_test: error: incorrect serial %d\n", elb->serial); return -EINVAL; } if (elts[ela->serial] != ela || elts[elb->serial] != elb) { printk(KERN_ERR "list_sort_test: error: phantom element\n"); return -EINVAL; } if (ela->poison1 != TEST_POISON1 || ela->poison2 != TEST_POISON2) { printk(KERN_ERR "list_sort_test: error: bad poison: %#x/%#x\n", ela->poison1, ela->poison2); return -EINVAL; } if (elb->poison1 != TEST_POISON1 || elb->poison2 != TEST_POISON2) { printk(KERN_ERR "list_sort_test: 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 = -EINVAL; struct debug_el *el; struct list_head *cur, *tmp; LIST_HEAD(head); printk(KERN_DEBUG "list_sort_test: start testing list_sort()\n"); elts = kmalloc(sizeof(void *) * TEST_LIST_LEN, GFP_KERNEL); if (!elts) { printk(KERN_ERR "list_sort_test: error: cannot allocate " "memory\n"); goto exit; } for (i = 0; i < TEST_LIST_LEN; i++) { el = kmalloc(sizeof(*el), GFP_KERNEL); if (!el) { printk(KERN_ERR "list_sort_test: 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); for (cur = head.next; cur->next != &head; cur = cur->next) { struct debug_el *el1; int cmp_result; if (cur->next->prev != cur) { printk(KERN_ERR "list_sort_test: error: list is " "corrupted\n"); goto exit; } cmp_result = cmp(NULL, cur, cur->next); if (cmp_result > 0) { printk(KERN_ERR "list_sort_test: 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) { printk(KERN_ERR "list_sort_test: error: order of " "equivalent elements not preserved\n"); goto exit; } if (check(el, el1)) { printk(KERN_ERR "list_sort_test: error: element check " "failed\n"); goto exit; } count++; } if (count != TEST_LIST_LEN) { printk(KERN_ERR "list_sort_test: error: bad list length %d", count); goto exit; } err = 0;exit: kfree(elts); list_for_each_safe(cur, tmp, &head) { list_del(cur); kfree(container_of(cur, struct debug_el, list)); } return err;}module_init(list_sort_test);#endif /* CONFIG_TEST_LIST_SORT */
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/list_sort.h>
#include <linux/slab.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;
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.
*/
(*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 passed to"
" list_sort() 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/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) {
printk(KERN_ERR "list_sort_test: error: incorrect serial %d\n",
ela->serial);
return -EINVAL;
}
if (elb->serial >= TEST_LIST_LEN) {
printk(KERN_ERR "list_sort_test: error: incorrect serial %d\n",
elb->serial);
return -EINVAL;
}
if (elts[ela->serial] != ela || elts[elb->serial] != elb) {
printk(KERN_ERR "list_sort_test: error: phantom element\n");
return -EINVAL;
}
if (ela->poison1 != TEST_POISON1 || ela->poison2 != TEST_POISON2) {
printk(KERN_ERR "list_sort_test: error: bad poison: %#x/%#x\n",
ela->poison1, ela->poison2);
return -EINVAL;
}
if (elb->poison1 != TEST_POISON1 || elb->poison2 != TEST_POISON2) {
printk(KERN_ERR "list_sort_test: 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 = -EINVAL;
struct debug_el *el;
struct list_head *cur, *tmp;
LIST_HEAD(head);
printk(KERN_DEBUG "list_sort_test: start testing list_sort()\n");
elts = kmalloc(sizeof(void *) * TEST_LIST_LEN, GFP_KERNEL);
if (!elts) {
printk(KERN_ERR "list_sort_test: error: cannot allocate "
"memory\n");
goto exit;
}
for (i = 0; i < TEST_LIST_LEN; i++) {
el = kmalloc(sizeof(*el), GFP_KERNEL);
if (!el) {
printk(KERN_ERR "list_sort_test: 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);
for (cur = head.next; cur->next != &head; cur = cur->next) {
struct debug_el *el1;
int cmp_result;
if (cur->next->prev != cur) {
printk(KERN_ERR "list_sort_test: error: list is "
"corrupted\n");
goto exit;
}
cmp_result = cmp(NULL, cur, cur->next);
if (cmp_result > 0) {
printk(KERN_ERR "list_sort_test: 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) {
printk(KERN_ERR "list_sort_test: error: order of "
"equivalent elements not preserved\n");
goto exit;
}
if (check(el, el1)) {
printk(KERN_ERR "list_sort_test: error: element check "
"failed\n");
goto exit;
}
count++;
}
if (count != TEST_LIST_LEN) {
printk(KERN_ERR "list_sort_test: error: bad list length %d",
count);
goto exit;
}
err = 0;
exit:
kfree(elts);
list_for_each_safe(cur, tmp, &head) {
list_del(cur);
kfree(container_of(cur, struct debug_el, list));
}
return err;
}
module_init(list_sort_test);
#endif /* CONFIG_TEST_LIST_SORT */