#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, tail); 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 DEBUG_LIST_SORTstruct debug_el { struct list_head l_h; int value; unsigned serial;}; static int cmp(void *priv, struct list_head *a, struct list_head *b){ return container_of(a, struct debug_el, l_h)->value - container_of(b, struct debug_el, l_h)->value;} /* * The pattern of set bits in the list length determines which cases * are hit in list_sort(). */#define LIST_SORT_TEST_LENGTH (512+128+2) /* not including head */ static int __init list_sort_test(void){ int i, r = 1, count; struct list_head *head = kmalloc(sizeof(*head), GFP_KERNEL); struct list_head *cur; printk(KERN_WARNING "testing list_sort()\n"); cur = head; for (i = 0; i < LIST_SORT_TEST_LENGTH; i++) { struct debug_el *el = kmalloc(sizeof(*el), GFP_KERNEL); BUG_ON(!el); /* force some equivalencies */ el->value = (r = (r * 725861) % 6599) % (LIST_SORT_TEST_LENGTH/3); el->serial = i; el->l_h.prev = cur; cur->next = &el->l_h; cur = cur->next; } head->prev = cur; list_sort(NULL, head, cmp); count = 1; for (cur = head->next; cur->next != head; cur = cur->next) { struct debug_el *el = container_of(cur, struct debug_el, l_h); int cmp_result = cmp(NULL, cur, cur->next); if (cur->next->prev != cur) { printk(KERN_EMERG "list_sort() returned " "a corrupted list!\n"); return 1; } else if (cmp_result > 0) { printk(KERN_EMERG "list_sort() failed to sort!\n"); return 1; } else if (cmp_result == 0 && el->serial >= container_of(cur->next, struct debug_el, l_h)->serial) { printk(KERN_EMERG "list_sort() failed to preserve order" " of equivalent elements!\n"); return 1; } kfree(cur->prev); count++; } kfree(cur); if (count != LIST_SORT_TEST_LENGTH) { printk(KERN_EMERG "list_sort() returned list of" "different length!\n"); return 1; } return 0;}module_init(list_sort_test);#endif
#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, tail);
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 DEBUG_LIST_SORT
struct debug_el {
struct list_head l_h;
int value;
unsigned serial;
};
static int cmp(void *priv, struct list_head *a, struct list_head *b)
{
return container_of(a, struct debug_el, l_h)->value
- container_of(b, struct debug_el, l_h)->value;
}
/*
* The pattern of set bits in the list length determines which cases
* are hit in list_sort().
*/
#define LIST_SORT_TEST_LENGTH (512+128+2) /* not including head */
static int __init list_sort_test(void)
{
int i, r = 1, count;
struct list_head *head = kmalloc(sizeof(*head), GFP_KERNEL);
struct list_head *cur;
printk(KERN_WARNING "testing list_sort()\n");
cur = head;
for (i = 0; i < LIST_SORT_TEST_LENGTH; i++) {
struct debug_el *el = kmalloc(sizeof(*el), GFP_KERNEL);
BUG_ON(!el);
/* force some equivalencies */
el->value = (r = (r * 725861) % 6599) % (LIST_SORT_TEST_LENGTH/3);
el->serial = i;
el->l_h.prev = cur;
cur->next = &el->l_h;
cur = cur->next;
}
head->prev = cur;
list_sort(NULL, head, cmp);
count = 1;
for (cur = head->next; cur->next != head; cur = cur->next) {
struct debug_el *el = container_of(cur, struct debug_el, l_h);
int cmp_result = cmp(NULL, cur, cur->next);
if (cur->next->prev != cur) {
printk(KERN_EMERG "list_sort() returned "
"a corrupted list!\n");
return 1;
} else if (cmp_result > 0) {
printk(KERN_EMERG "list_sort() failed to sort!\n");
return 1;
} else if (cmp_result == 0 &&
el->serial >= container_of(cur->next,
struct debug_el, l_h)->serial) {
printk(KERN_EMERG "list_sort() failed to preserve order"
" of equivalent elements!\n");
return 1;
}
kfree(cur->prev);
count++;
}
kfree(cur);
if (count != LIST_SORT_TEST_LENGTH) {
printk(KERN_EMERG "list_sort() returned list of"
"different length!\n");
return 1;
}
return 0;
}
module_init(list_sort_test);
#endif