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7259fa0424
Memory allocation only happens in the self test, just as random numbers are only used there. So move the inclusion of slab.h inside the CONFIG_TEST_LIST_SORT. We don't need module.h and all of the stuff it carries with it, so replace with export.h and compiler.h. Unfortunately, the ARRAY_SIZE macro from kernel.h requires the user to ensure bug.h is also included (for BUILD_BUG_ON_ZERO, used by __must_be_array). We used to get that through some maze of nested includes, but just include it explicitly. linux/string.h is then only included implicitly through kernel.h->printk.h->dynamic_debug.h, but only if !CONFIG_DYNAMIC_DEBUG, so just include it explicitly (for memset). objdump -d says the generated code is the same, and wc -l says that lib/.list_sort.o.cmd went from 579 to 165 lines. Signed-off-by: Rasmus Villemoes <linux@rasmusvillemoes.dk> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
294 lines
6.8 KiB
C
294 lines
6.8 KiB
C
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#define pr_fmt(fmt) "list_sort_test: " fmt
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#include <linux/kernel.h>
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#include <linux/bug.h>
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#include <linux/compiler.h>
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#include <linux/export.h>
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#include <linux/string.h>
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#include <linux/list_sort.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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u8 count = 0;
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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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if (unlikely(!(++count)))
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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 too long for 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/slab.h>
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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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pr_err("error: incorrect serial %d\n", 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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pr_err("error: incorrect serial %d\n", 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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pr_err("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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pr_err("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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pr_err("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 = -ENOMEM;
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struct debug_el *el;
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struct list_head *cur;
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LIST_HEAD(head);
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pr_debug("start testing list_sort()\n");
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elts = kcalloc(TEST_LIST_LEN, sizeof(*elts), GFP_KERNEL);
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if (!elts) {
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pr_err("error: cannot allocate memory\n");
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return err;
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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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pr_err("error: cannot 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 = prandom_u32() % (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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err = -EINVAL;
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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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pr_err("error: list is 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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pr_err("error: list is not 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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pr_err("error: order of equivalent elements not "
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"preserved\n");
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goto exit;
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}
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if (check(el, el1)) {
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pr_err("error: element check 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 (head.prev != cur) {
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pr_err("error: list is corrupted\n");
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goto exit;
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}
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if (count != TEST_LIST_LEN) {
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pr_err("error: bad list length %d", 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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for (i = 0; i < TEST_LIST_LEN; i++)
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kfree(elts[i]);
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kfree(elts);
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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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