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041b78f232
Improve 'lib_sort()' test and check that: o 'cmp()' is called only for elements which were present in the original list, i.e., the 'a' and 'b' parameters are valid o the resulted (sorted) list consists onlly of the original elements o intdoruce "poison" fields to make sure data around 'struc list_head' field are not corrupted. Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@nokia.com> Cc: Don Mullis <don.mullis@gmail.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
292 lines
7.0 KiB
C
292 lines
7.0 KiB
C
#include <linux/kernel.h>
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#include <linux/module.h>
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#include <linux/list_sort.h>
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#include <linux/slab.h>
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#include <linux/list.h>
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#define MAX_LIST_LENGTH_BITS 20
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/*
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* Returns a list organized in an intermediate format suited
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* to chaining of merge() calls: null-terminated, no reserved or
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* sentinel head node, "prev" links not maintained.
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*/
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static struct list_head *merge(void *priv,
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int (*cmp)(void *priv, struct list_head *a,
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struct list_head *b),
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struct list_head *a, struct list_head *b)
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{
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struct list_head head, *tail = &head;
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while (a && b) {
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/* if equal, take 'a' -- important for sort stability */
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if ((*cmp)(priv, a, b) <= 0) {
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tail->next = a;
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a = a->next;
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} else {
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tail->next = b;
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b = b->next;
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}
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tail = tail->next;
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}
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tail->next = a?:b;
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return head.next;
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}
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/*
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* Combine final list merge with restoration of standard doubly-linked
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* list structure. This approach duplicates code from merge(), but
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* runs faster than the tidier alternatives of either a separate final
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* prev-link restoration pass, or maintaining the prev links
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* throughout.
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*/
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static void merge_and_restore_back_links(void *priv,
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int (*cmp)(void *priv, struct list_head *a,
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struct list_head *b),
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struct list_head *head,
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struct list_head *a, struct list_head *b)
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{
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struct list_head *tail = head;
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while (a && b) {
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/* if equal, take 'a' -- important for sort stability */
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if ((*cmp)(priv, a, b) <= 0) {
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tail->next = a;
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a->prev = tail;
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a = a->next;
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} else {
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tail->next = b;
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b->prev = tail;
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b = b->next;
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}
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tail = tail->next;
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}
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tail->next = a ? : b;
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do {
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/*
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* In worst cases this loop may run many iterations.
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* Continue callbacks to the client even though no
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* element comparison is needed, so the client's cmp()
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* routine can invoke cond_resched() periodically.
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*/
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(*cmp)(priv, tail->next, tail->next);
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tail->next->prev = tail;
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tail = tail->next;
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} while (tail->next);
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tail->next = head;
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head->prev = tail;
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}
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/**
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* list_sort - sort a list
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* @priv: private data, opaque to list_sort(), passed to @cmp
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* @head: the list to sort
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* @cmp: the elements comparison function
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*
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* This function implements "merge sort", which has O(nlog(n))
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* complexity.
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*
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* The comparison function @cmp must return a negative value if @a
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* should sort before @b, and a positive value if @a should sort after
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* @b. If @a and @b are equivalent, and their original relative
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* ordering is to be preserved, @cmp must return 0.
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*/
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void list_sort(void *priv, struct list_head *head,
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int (*cmp)(void *priv, struct list_head *a,
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struct list_head *b))
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{
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struct list_head *part[MAX_LIST_LENGTH_BITS+1]; /* sorted partial lists
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-- last slot is a sentinel */
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int lev; /* index into part[] */
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int max_lev = 0;
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struct list_head *list;
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if (list_empty(head))
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return;
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memset(part, 0, sizeof(part));
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head->prev->next = NULL;
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list = head->next;
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while (list) {
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struct list_head *cur = list;
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list = list->next;
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cur->next = NULL;
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for (lev = 0; part[lev]; lev++) {
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cur = merge(priv, cmp, part[lev], cur);
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part[lev] = NULL;
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}
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if (lev > max_lev) {
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if (unlikely(lev >= ARRAY_SIZE(part)-1)) {
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printk_once(KERN_DEBUG "list passed to"
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" list_sort() too long for"
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" efficiency\n");
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lev--;
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}
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max_lev = lev;
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}
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part[lev] = cur;
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}
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for (lev = 0; lev < max_lev; lev++)
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if (part[lev])
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list = merge(priv, cmp, part[lev], list);
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merge_and_restore_back_links(priv, cmp, head, part[max_lev], list);
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}
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EXPORT_SYMBOL(list_sort);
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#ifdef CONFIG_TEST_LIST_SORT
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#include <linux/random.h>
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/*
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* The pattern of set bits in the list length determines which cases
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* are hit in list_sort().
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*/
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#define TEST_LIST_LEN (512+128+2) /* not including head */
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#define TEST_POISON1 0xDEADBEEF
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#define TEST_POISON2 0xA324354C
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struct debug_el {
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unsigned int poison1;
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struct list_head list;
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unsigned int poison2;
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int value;
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unsigned serial;
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};
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/* Array, containing pointers to all elements in the test list */
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static struct debug_el **elts __initdata;
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static int __init check(struct debug_el *ela, struct debug_el *elb)
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{
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if (ela->serial >= TEST_LIST_LEN) {
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printk(KERN_ERR "list_sort_test: error: incorrect serial %d\n",
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ela->serial);
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return -EINVAL;
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}
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if (elb->serial >= TEST_LIST_LEN) {
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printk(KERN_ERR "list_sort_test: error: incorrect serial %d\n",
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elb->serial);
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return -EINVAL;
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}
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if (elts[ela->serial] != ela || elts[elb->serial] != elb) {
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printk(KERN_ERR "list_sort_test: error: phantom element\n");
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return -EINVAL;
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}
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if (ela->poison1 != TEST_POISON1 || ela->poison2 != TEST_POISON2) {
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printk(KERN_ERR "list_sort_test: error: bad poison: %#x/%#x\n",
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ela->poison1, ela->poison2);
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return -EINVAL;
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}
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if (elb->poison1 != TEST_POISON1 || elb->poison2 != TEST_POISON2) {
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printk(KERN_ERR "list_sort_test: error: bad poison: %#x/%#x\n",
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elb->poison1, elb->poison2);
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return -EINVAL;
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}
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return 0;
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}
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static int __init cmp(void *priv, struct list_head *a, struct list_head *b)
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{
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struct debug_el *ela, *elb;
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ela = container_of(a, struct debug_el, list);
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elb = container_of(b, struct debug_el, list);
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check(ela, elb);
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return ela->value - elb->value;
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}
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static int __init list_sort_test(void)
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{
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int i, count = 1, err = -EINVAL;
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struct debug_el *el;
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struct list_head *cur, *tmp;
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LIST_HEAD(head);
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printk(KERN_DEBUG "list_sort_test: start testing list_sort()\n");
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elts = kmalloc(sizeof(void *) * TEST_LIST_LEN, GFP_KERNEL);
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if (!elts) {
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printk(KERN_ERR "list_sort_test: error: cannot allocate "
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"memory\n");
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goto exit;
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}
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for (i = 0; i < TEST_LIST_LEN; i++) {
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el = kmalloc(sizeof(*el), GFP_KERNEL);
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if (!el) {
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printk(KERN_ERR "list_sort_test: error: cannot "
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"allocate memory\n");
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goto exit;
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}
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/* force some equivalencies */
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el->value = random32() % (TEST_LIST_LEN/3);
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el->serial = i;
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el->poison1 = TEST_POISON1;
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el->poison2 = TEST_POISON2;
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elts[i] = el;
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list_add_tail(&el->list, &head);
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}
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list_sort(NULL, &head, cmp);
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for (cur = head.next; cur->next != &head; cur = cur->next) {
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struct debug_el *el1;
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int cmp_result;
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if (cur->next->prev != cur) {
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printk(KERN_ERR "list_sort_test: error: list is "
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"corrupted\n");
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goto exit;
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}
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cmp_result = cmp(NULL, cur, cur->next);
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if (cmp_result > 0) {
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printk(KERN_ERR "list_sort_test: error: list is not "
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"sorted\n");
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goto exit;
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}
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el = container_of(cur, struct debug_el, list);
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el1 = container_of(cur->next, struct debug_el, list);
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if (cmp_result == 0 && el->serial >= el1->serial) {
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printk(KERN_ERR "list_sort_test: error: order of "
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"equivalent elements not preserved\n");
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goto exit;
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}
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if (check(el, el1)) {
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printk(KERN_ERR "list_sort_test: error: element check "
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"failed\n");
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goto exit;
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}
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count++;
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}
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if (count != TEST_LIST_LEN) {
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printk(KERN_ERR "list_sort_test: error: bad list length %d",
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count);
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goto exit;
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}
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err = 0;
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exit:
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kfree(elts);
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list_for_each_safe(cur, tmp, &head) {
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list_del(cur);
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kfree(container_of(cur, struct debug_el, list));
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}
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return err;
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}
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module_init(list_sort_test);
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#endif /* CONFIG_TEST_LIST_SORT */
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