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1// SPDX-License-Identifier: GPL-2.0-or-later2/*3 * lib/plist.c4 *5 * Descending-priority-sorted double-linked list6 *7 * (C) 2002-2003 Intel Corp8 * Inaky Perez-Gonzalez <inaky.perez-gonzalez@intel.com>.9 *10 * 2001-2005 (c) MontaVista Software, Inc.11 * Daniel Walker <dwalker@mvista.com>12 *13 * (C) 2005 Thomas Gleixner <tglx@linutronix.de>14 *15 * Simplifications of the original code by16 * Oleg Nesterov <oleg@tv-sign.ru>17 *18 * Based on simple lists (include/linux/list.h).19 *20 * This file contains the add / del functions which are considered to21 * be too large to inline. See include/linux/plist.h for further22 * information.23 */24 25#include <linux/bug.h>26#include <linux/plist.h>27 28#ifdef CONFIG_DEBUG_PLIST29 30static struct plist_head test_head;31 32static void plist_check_prev_next(struct list_head *t, struct list_head *p,33 struct list_head *n)34{35 WARN(n->prev != p || p->next != n,36 "top: %p, n: %p, p: %p\n"37 "prev: %p, n: %p, p: %p\n"38 "next: %p, n: %p, p: %p\n",39 t, t->next, t->prev,40 p, p->next, p->prev,41 n, n->next, n->prev);42}43 44static void plist_check_list(struct list_head *top)45{46 struct list_head *prev = top, *next = top->next;47 48 plist_check_prev_next(top, prev, next);49 while (next != top) {50 WRITE_ONCE(prev, next);51 WRITE_ONCE(next, prev->next);52 plist_check_prev_next(top, prev, next);53 }54}55 56static void plist_check_head(struct plist_head *head)57{58 if (!plist_head_empty(head))59 plist_check_list(&plist_first(head)->prio_list);60 plist_check_list(&head->node_list);61}62 63#else64# define plist_check_head(h) do { } while (0)65#endif66 67/**68 * plist_add - add @node to @head69 *70 * @node: &struct plist_node pointer71 * @head: &struct plist_head pointer72 */73void plist_add(struct plist_node *node, struct plist_head *head)74{75 struct plist_node *first, *iter, *prev = NULL, *last, *reverse_iter;76 struct list_head *node_next = &head->node_list;77 78 plist_check_head(head);79 WARN_ON(!plist_node_empty(node));80 WARN_ON(!list_empty(&node->prio_list));81 82 if (plist_head_empty(head))83 goto ins_node;84 85 first = iter = plist_first(head);86 last = reverse_iter = list_entry(first->prio_list.prev, struct plist_node, prio_list);87 88 do {89 if (node->prio < iter->prio) {90 node_next = &iter->node_list;91 break;92 } else if (node->prio >= reverse_iter->prio) {93 prev = reverse_iter;94 iter = list_entry(reverse_iter->prio_list.next,95 struct plist_node, prio_list);96 if (likely(reverse_iter != last))97 node_next = &iter->node_list;98 break;99 }100 101 prev = iter;102 iter = list_entry(iter->prio_list.next,103 struct plist_node, prio_list);104 reverse_iter = list_entry(reverse_iter->prio_list.prev,105 struct plist_node, prio_list);106 } while (iter != first);107 108 if (!prev || prev->prio != node->prio)109 list_add_tail(&node->prio_list, &iter->prio_list);110ins_node:111 list_add_tail(&node->node_list, node_next);112 113 plist_check_head(head);114}115 116/**117 * plist_del - Remove a @node from plist.118 *119 * @node: &struct plist_node pointer - entry to be removed120 * @head: &struct plist_head pointer - list head121 */122void plist_del(struct plist_node *node, struct plist_head *head)123{124 plist_check_head(head);125 126 if (!list_empty(&node->prio_list)) {127 if (node->node_list.next != &head->node_list) {128 struct plist_node *next;129 130 next = list_entry(node->node_list.next,131 struct plist_node, node_list);132 133 /* add the next plist_node into prio_list */134 if (list_empty(&next->prio_list))135 list_add(&next->prio_list, &node->prio_list);136 }137 list_del_init(&node->prio_list);138 }139 140 list_del_init(&node->node_list);141 142 plist_check_head(head);143}144 145/**146 * plist_requeue - Requeue @node at end of same-prio entries.147 *148 * This is essentially an optimized plist_del() followed by149 * plist_add(). It moves an entry already in the plist to150 * after any other same-priority entries.151 *152 * @node: &struct plist_node pointer - entry to be moved153 * @head: &struct plist_head pointer - list head154 */155void plist_requeue(struct plist_node *node, struct plist_head *head)156{157 struct plist_node *iter;158 struct list_head *node_next = &head->node_list;159 160 plist_check_head(head);161 BUG_ON(plist_head_empty(head));162 BUG_ON(plist_node_empty(node));163 164 if (node == plist_last(head))165 return;166 167 iter = plist_next(node);168 169 if (node->prio != iter->prio)170 return;171 172 plist_del(node, head);173 174 plist_for_each_continue(iter, head) {175 if (node->prio != iter->prio) {176 node_next = &iter->node_list;177 break;178 }179 }180 list_add_tail(&node->node_list, node_next);181 182 plist_check_head(head);183}184 185#ifdef CONFIG_DEBUG_PLIST186#include <linux/sched.h>187#include <linux/sched/clock.h>188#include <linux/module.h>189#include <linux/init.h>190 191static struct plist_node __initdata test_node[241];192 193static void __init plist_test_check(int nr_expect)194{195 struct plist_node *first, *prio_pos, *node_pos;196 197 if (plist_head_empty(&test_head)) {198 BUG_ON(nr_expect != 0);199 return;200 }201 202 prio_pos = first = plist_first(&test_head);203 plist_for_each(node_pos, &test_head) {204 if (nr_expect-- < 0)205 break;206 if (node_pos == first)207 continue;208 if (node_pos->prio == prio_pos->prio) {209 BUG_ON(!list_empty(&node_pos->prio_list));210 continue;211 }212 213 BUG_ON(prio_pos->prio > node_pos->prio);214 BUG_ON(prio_pos->prio_list.next != &node_pos->prio_list);215 prio_pos = node_pos;216 }217 218 BUG_ON(nr_expect != 0);219 BUG_ON(prio_pos->prio_list.next != &first->prio_list);220}221 222static void __init plist_test_requeue(struct plist_node *node)223{224 plist_requeue(node, &test_head);225 226 if (node != plist_last(&test_head))227 BUG_ON(node->prio == plist_next(node)->prio);228}229 230static int __init plist_test(void)231{232 int nr_expect = 0, i, loop;233 unsigned int r = local_clock();234 235 printk(KERN_DEBUG "start plist test\n");236 plist_head_init(&test_head);237 for (i = 0; i < ARRAY_SIZE(test_node); i++)238 plist_node_init(test_node + i, 0);239 240 for (loop = 0; loop < 1000; loop++) {241 r = r * 193939 % 47629;242 i = r % ARRAY_SIZE(test_node);243 if (plist_node_empty(test_node + i)) {244 r = r * 193939 % 47629;245 test_node[i].prio = r % 99;246 plist_add(test_node + i, &test_head);247 nr_expect++;248 } else {249 plist_del(test_node + i, &test_head);250 nr_expect--;251 }252 plist_test_check(nr_expect);253 if (!plist_node_empty(test_node + i)) {254 plist_test_requeue(test_node + i);255 plist_test_check(nr_expect);256 }257 }258 259 for (i = 0; i < ARRAY_SIZE(test_node); i++) {260 if (plist_node_empty(test_node + i))261 continue;262 plist_del(test_node + i, &test_head);263 nr_expect--;264 plist_test_check(nr_expect);265 }266 267 printk(KERN_DEBUG "end plist test\n");268 269 /* Worst case test for plist_add() */270 unsigned int test_data[241];271 272 for (i = 0; i < ARRAY_SIZE(test_data); i++)273 test_data[i] = i;274 275 ktime_t start, end, time_elapsed = 0;276 277 plist_head_init(&test_head);278 279 for (i = 0; i < ARRAY_SIZE(test_node); i++) {280 plist_node_init(test_node + i, 0);281 test_node[i].prio = test_data[i];282 }283 284 for (i = 0; i < ARRAY_SIZE(test_node); i++) {285 if (plist_node_empty(test_node + i)) {286 start = ktime_get();287 plist_add(test_node + i, &test_head);288 end = ktime_get();289 time_elapsed += (end - start);290 }291 }292 293 pr_debug("plist_add worst case test time elapsed %lld\n", time_elapsed);294 return 0;295}296 297module_init(plist_test);298 299#endif300