new file mode 100644
@@ -0,0 +1,157 @@
+/*
+ * list_sort.c: merge sort implementation for linked lists
+ * Copied from the Linux kernel (lib/list_sort.c)
+ *
+ * This program is free software; you can redistribute it and/or modify it
+ * under the terms and conditions of the GNU General Public License,
+ * version 2, as published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for
+ * more details.
+ *
+ * You should have received a copy of the GNU General Public License along with
+ * this program; If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include <xen/lib.h>
+#include <xen/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)) {
+ dprintk(XENLOG_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);
new file mode 100644
@@ -0,0 +1,11 @@
+#ifndef _LINUX_LIST_SORT_H
+#define _LINUX_LIST_SORT_H
+
+#include <xen/types.h>
+
+struct list_head;
+
+void list_sort(void *priv, struct list_head *head,
+ int (*cmp)(void *priv, struct list_head *a,
+ struct list_head *b));
+#endif
This pulls in Linux' list_sort.c, which is a merge sort implementation for linked lists. Apart from adding a full featured license header and adjusting the #include file, nothing has been changed in this code. Signed-off-by: Andre Przywara <andre.przywara@linaro.org> --- Changelog v1 ... v2: - split out to just contain Linux code dump xen/common/list_sort.c | 157 ++++++++++++++++++++++++++++++++++++++++++++ xen/include/xen/list_sort.h | 11 ++++ 2 files changed, 168 insertions(+) create mode 100644 xen/common/list_sort.c create mode 100644 xen/include/xen/list_sort.h