lib/list_sort.c - linux - Git at Google


 #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;
 }
 module_init(list_sort_test);
 #endif /* CONFIG_TEST_LIST_SORT */

	#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;
	}
	module_init(list_sort_test);
	#endif /* CONFIG_TEST_LIST_SORT */