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#include 

#include 

#include 

#include 

#include 

#include 

 * 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;

		/* 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;

		/* 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;

		/*

		 * 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 = tail->next;

	} while (tail->next);

	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;

		return;

	list = head->next;

		struct list_head *cur = list;

		list = list->next;

		cur->next = NULL;

			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;

	}

		if (part[lev])

			list = merge(priv, cmp, part[lev], list);

}

EXPORT_SYMBOL(list_sort);

#include 

 * 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_POISON2 0xA324354C

	unsigned int poison1;

	struct list_head list;

	unsigned int poison2;

	int value;

	unsigned serial;

};

static struct debug_el **elts __initdata;

{

	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;

}

{

	struct debug_el *ela, *elb;

	elb = container_of(b, struct debug_el, list);

	return ela->value - elb->value;

}

{

	int i, count = 1, err = -ENOMEM;

	struct debug_el *el;

	struct list_head *cur;

	LIST_HEAD(head);

	if (!elts) {

		pr_err("error: cannot allocate memory\n");

		return err;

	}

		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);

	}

	for (cur = head.next; cur->next != &head; cur = cur->next) {

		struct debug_el *el1;

		int cmp_result;

			pr_err("error: list is corrupted\n");

			goto exit;

		}

		if (cmp_result > 0) {

			pr_err("error: list is not sorted\n");

			goto exit;

		}

		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;

		}

			pr_err("error: element check failed\n");

			goto exit;

		}

		count++;

	}

	if (head.prev != cur) {

		pr_err("error: list is corrupted\n");

		goto exit;

	}

		pr_err("error: bad list length %d", count);

		goto exit;

	}

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 */