#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, passed to @cmp
+ * 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 has been implemented by Mark J Roberts <mjr@znex.org>. It
- * implements "merge sort" which has O(nlog(n)) complexity. The list is sorted
- * in ascending order.
+ * This function implements "merge sort", which has O(nlog(n))
+ * complexity.
*
- * The comparison function @cmp is supposed to return a negative value if @a is
- * less than @b, and a positive value if @a is greater than @b. If @a and @b
- * are equivalent, then it does not matter what this function returns.
+ * 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))
+ int (*cmp)(void *priv, struct list_head *a,
+ struct list_head *b))
{
- struct list_head *p, *q, *e, *list, *tail, *oldhead;
- int insize, nmerges, psize, qsize, i;
+ 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;
- list_del(head);
- insize = 1;
- for (;;) {
- p = oldhead = list;
- list = tail = NULL;
- nmerges = 0;
-
- while (p) {
- nmerges++;
- q = p;
- psize = 0;
- for (i = 0; i < insize; i++) {
- psize++;
- q = q->next == oldhead ? NULL : q->next;
- if (!q)
- break;
- }
- qsize = insize;
- while (psize > 0 || (qsize > 0 && q)) {
- if (!psize) {
- e = q;
- q = q->next;
- qsize--;
- if (q == oldhead)
- q = NULL;
- } else if (!qsize || !q) {
- e = p;
- p = p->next;
- psize--;
- if (p == oldhead)
- p = NULL;
- } else if (cmp(priv, p, q) <= 0) {
- e = p;
- p = p->next;
- psize--;
- if (p == oldhead)
- p = NULL;
- } else {
- e = q;
- q = q->next;
- qsize--;
- if (q == oldhead)
- q = NULL;
- }
- if (tail)
- tail->next = e;
- else
- list = e;
- e->prev = tail;
- tail = e;
+ 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--;
}
- p = q;
+ 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>
- tail->next = list;
- list->prev = tail;
+/*
+ * 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
- if (nmerges <= 1)
- break;
+struct debug_el {
+ unsigned int poison1;
+ struct list_head list;
+ unsigned int poison2;
+ int value;
+ unsigned serial;
+};
- insize *= 2;
+/* 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);
- head->next = list;
- head->prev = list->prev;
- list->prev->next = head;
- list->prev = head;
+ check(ela, elb);
+ return ela->value - elb->value;
}
-EXPORT_SYMBOL(list_sort);
+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 = random32() % (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 */
projects / linux-flexiantxendom0-3.2.10.git / blobdiff