1 files changed, 263 insertions, 0 deletions
diff --git a/lib/plist.c b/lib/plist.c
new file mode 100644
index 0000000000..0d86ed7a76
--- /dev/null
+++ b/lib/plist.c
@@ -0,0 +1,263 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * lib/plist.c
+ *
+ * Descending-priority-sorted double-linked list
+ *
+ * (C) 2002-2003 Intel Corp
+ * Inaky Perez-Gonzalez <inaky.perez-gonzalez@intel.com>.
+ *
+ * 2001-2005 (c) MontaVista Software, Inc.
+ * Daniel Walker <dwalker@mvista.com>
+ *
+ * (C) 2005 Thomas Gleixner <tglx@linutronix.de>
+ *
+ * Simplifications of the original code by
+ * Oleg Nesterov <oleg@tv-sign.ru>
+ *
+ * Based on simple lists (include/linux/list.h).
+ *
+ * This file contains the add / del functions which are considered to
+ * be too large to inline. See include/linux/plist.h for further
+ * information.
+ */
+
+#include <linux/bug.h>
+#include <linux/plist.h>
+
+#ifdef CONFIG_DEBUG_PLIST
+
+static struct plist_head test_head;
+
+static void plist_check_prev_next(struct list_head *t, struct list_head *p,
+				  struct list_head *n)
+{
+	WARN(n->prev != p || p->next != n,
+			"top: %p, n: %p, p: %p\n"
+			"prev: %p, n: %p, p: %p\n"
+			"next: %p, n: %p, p: %p\n",
+			 t, t->next, t->prev,
+			p, p->next, p->prev,
+			n, n->next, n->prev);
+}
+
+static void plist_check_list(struct list_head *top)
+{
+	struct list_head *prev = top, *next = top->next;
+
+	plist_check_prev_next(top, prev, next);
+	while (next != top) {
+		prev = next;
+		next = prev->next;
+		plist_check_prev_next(top, prev, next);
+	}
+}
+
+static void plist_check_head(struct plist_head *head)
+{
+	if (!plist_head_empty(head))
+		plist_check_list(&plist_first(head)->prio_list);
+	plist_check_list(&head->node_list);
+}
+
+#else
+# define plist_check_head(h)	do { } while (0)
+#endif
+
+/**
+ * plist_add - add @node to @head
+ *
+ * @node:	&struct plist_node pointer
+ * @head:	&struct plist_head pointer
+ */
+void plist_add(struct plist_node *node, struct plist_head *head)
+{
+	struct plist_node *first, *iter, *prev = NULL;
+	struct list_head *node_next = &head->node_list;
+
+	plist_check_head(head);
+	WARN_ON(!plist_node_empty(node));
+	WARN_ON(!list_empty(&node->prio_list));
+
+	if (plist_head_empty(head))
+		goto ins_node;
+
+	first = iter = plist_first(head);
+
+	do {
+		if (node->prio < iter->prio) {
+			node_next = &iter->node_list;
+			break;
+		}
+
+		prev = iter;
+		iter = list_entry(iter->prio_list.next,
+				struct plist_node, prio_list);
+	} while (iter != first);
+
+	if (!prev || prev->prio != node->prio)
+		list_add_tail(&node->prio_list, &iter->prio_list);
+ins_node:
+	list_add_tail(&node->node_list, node_next);
+
+	plist_check_head(head);
+}
+
+/**
+ * plist_del - Remove a @node from plist.
+ *
+ * @node:	&struct plist_node pointer - entry to be removed
+ * @head:	&struct plist_head pointer - list head
+ */
+void plist_del(struct plist_node *node, struct plist_head *head)
+{
+	plist_check_head(head);
+
+	if (!list_empty(&node->prio_list)) {
+		if (node->node_list.next != &head->node_list) {
+			struct plist_node *next;
+
+			next = list_entry(node->node_list.next,
+					struct plist_node, node_list);
+
+			/* add the next plist_node into prio_list */
+			if (list_empty(&next->prio_list))
+				list_add(&next->prio_list, &node->prio_list);
+		}
+		list_del_init(&node->prio_list);
+	}
+
+	list_del_init(&node->node_list);
+
+	plist_check_head(head);
+}
+
+/**
+ * plist_requeue - Requeue @node at end of same-prio entries.
+ *
+ * This is essentially an optimized plist_del() followed by
+ * plist_add().  It moves an entry already in the plist to
+ * after any other same-priority entries.
+ *
+ * @node:	&struct plist_node pointer - entry to be moved
+ * @head:	&struct plist_head pointer - list head
+ */
+void plist_requeue(struct plist_node *node, struct plist_head *head)
+{
+	struct plist_node *iter;
+	struct list_head *node_next = &head->node_list;
+
+	plist_check_head(head);
+	BUG_ON(plist_head_empty(head));
+	BUG_ON(plist_node_empty(node));
+
+	if (node == plist_last(head))
+		return;
+
+	iter = plist_next(node);
+
+	if (node->prio != iter->prio)
+		return;
+
+	plist_del(node, head);
+
+	plist_for_each_continue(iter, head) {
+		if (node->prio != iter->prio) {
+			node_next = &iter->node_list;
+			break;
+		}
+	}
+	list_add_tail(&node->node_list, node_next);
+
+	plist_check_head(head);
+}
+
+#ifdef CONFIG_DEBUG_PLIST
+#include <linux/sched.h>
+#include <linux/sched/clock.h>
+#include <linux/module.h>
+#include <linux/init.h>
+
+static struct plist_node __initdata test_node[241];
+
+static void __init plist_test_check(int nr_expect)
+{
+	struct plist_node *first, *prio_pos, *node_pos;
+
+	if (plist_head_empty(&test_head)) {
+		BUG_ON(nr_expect != 0);
+		return;
+	}
+
+	prio_pos = first = plist_first(&test_head);
+	plist_for_each(node_pos, &test_head) {
+		if (nr_expect-- < 0)
+			break;
+		if (node_pos == first)
+			continue;
+		if (node_pos->prio == prio_pos->prio) {
+			BUG_ON(!list_empty(&node_pos->prio_list));
+			continue;
+		}
+
+		BUG_ON(prio_pos->prio > node_pos->prio);
+		BUG_ON(prio_pos->prio_list.next != &node_pos->prio_list);
+		prio_pos = node_pos;
+	}
+
+	BUG_ON(nr_expect != 0);
+	BUG_ON(prio_pos->prio_list.next != &first->prio_list);
+}
+
+static void __init plist_test_requeue(struct plist_node *node)
+{
+	plist_requeue(node, &test_head);
+
+	if (node != plist_last(&test_head))
+		BUG_ON(node->prio == plist_next(node)->prio);
+}
+
+static int  __init plist_test(void)
+{
+	int nr_expect = 0, i, loop;
+	unsigned int r = local_clock();
+
+	printk(KERN_DEBUG "start plist test\n");
+	plist_head_init(&test_head);
+	for (i = 0; i < ARRAY_SIZE(test_node); i++)
+		plist_node_init(test_node + i, 0);
+
+	for (loop = 0; loop < 1000; loop++) {
+		r = r * 193939 % 47629;
+		i = r % ARRAY_SIZE(test_node);
+		if (plist_node_empty(test_node + i)) {
+			r = r * 193939 % 47629;
+			test_node[i].prio = r % 99;
+			plist_add(test_node + i, &test_head);
+			nr_expect++;
+		} else {
+			plist_del(test_node + i, &test_head);
+			nr_expect--;
+		}
+		plist_test_check(nr_expect);
+		if (!plist_node_empty(test_node + i)) {
+			plist_test_requeue(test_node + i);
+			plist_test_check(nr_expect);
+		}
+	}
+
+	for (i = 0; i < ARRAY_SIZE(test_node); i++) {
+		if (plist_node_empty(test_node + i))
+			continue;
+		plist_del(test_node + i, &test_head);
+		nr_expect--;
+		plist_test_check(nr_expect);
+	}
+
+	printk(KERN_DEBUG "end plist test\n");
+	return 0;
+}
+
+module_init(plist_test);
+
+#endif