lib/plist.c

   1 // SPDX-License-Identifier: GPL-2.0-or-later
   2 /*
   3  * lib/plist.c
   4  *
   5  * Descending-priority-sorted double-linked list
   6  *
   7  * (C) 2002-2003 Intel Corp
   8  * 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 by
  16  * 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 to
  21  * be too large to inline. See include/linux/plist.h for further
  22  * information.
  23  */
  24
  25 #include <linux/bug.h>
  26 #include <linux/plist.h>
  27
  28 #ifdef CONFIG_DEBUG_PLIST
  29
  30 static struct plist_head test_head;
  31
  32 static 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
  44 static 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                 prev = next;
  51                 next = prev->next;
  52                 plist_check_prev_next(top, prev, next);
  53         }
  54 }
  55
  56 static 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 #else
  64 # define plist_check_head(h)    do { } while (0)
  65 #endif
  66
  67 /**
  68  * plist_add - add @node to @head
  69  *
  70  * @node:       &struct plist_node pointer
  71  * @head:       &struct plist_head pointer
  72  */
  73 void plist_add(struct plist_node *node, struct plist_head *head)
  74 {
  75         struct plist_node *first, *iter, *prev = NULL;
  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
  87         do {
  88                 if (node->prio < iter->prio) {
  89                         node_next = &iter->node_list;
  90                         break;
  91                 }
  92
  93                 prev = iter;
  94                 iter = list_entry(iter->prio_list.next,
  95                                 struct plist_node, prio_list);
  96         } while (iter != first);
  97
  98         if (!prev || prev->prio != node->prio)
  99                 list_add_tail(&node->prio_list, &iter->prio_list);
 100 ins_node:
 101         list_add_tail(&node->node_list, node_next);
 102
 103         plist_check_head(head);
 104 }
 105
 106 /**
 107  * plist_del - Remove a @node from plist.
 108  *
 109  * @node:       &struct plist_node pointer - entry to be removed
 110  * @head:       &struct plist_head pointer - list head
 111  */
 112 void plist_del(struct plist_node *node, struct plist_head *head)
 113 {
 114         plist_check_head(head);
 115
 116         if (!list_empty(&node->prio_list)) {
 117                 if (node->node_list.next != &head->node_list) {
 118                         struct plist_node *next;
 119
 120                         next = list_entry(node->node_list.next,
 121                                         struct plist_node, node_list);
 122
 123                         /* add the next plist_node into prio_list */
 124                         if (list_empty(&next->prio_list))
 125                                 list_add(&next->prio_list, &node->prio_list);
 126                 }
 127                 list_del_init(&node->prio_list);
 128         }
 129
 130         list_del_init(&node->node_list);
 131
 132         plist_check_head(head);
 133 }
 134
 135 /**
 136  * plist_requeue - Requeue @node at end of same-prio entries.
 137  *
 138  * This is essentially an optimized plist_del() followed by
 139  * plist_add().  It moves an entry already in the plist to
 140  * after any other same-priority entries.
 141  *
 142  * @node:       &struct plist_node pointer - entry to be moved
 143  * @head:       &struct plist_head pointer - list head
 144  */
 145 void plist_requeue(struct plist_node *node, struct plist_head *head)
 146 {
 147         struct plist_node *iter;
 148         struct list_head *node_next = &head->node_list;
 149
 150         plist_check_head(head);
 151         BUG_ON(plist_head_empty(head));
 152         BUG_ON(plist_node_empty(node));
 153
 154         if (node == plist_last(head))
 155                 return;
 156
 157         iter = plist_next(node);
 158
 159         if (node->prio != iter->prio)
 160                 return;
 161
 162         plist_del(node, head);
 163
 164         plist_for_each_continue(iter, head) {
 165                 if (node->prio != iter->prio) {
 166                         node_next = &iter->node_list;
 167                         break;
 168                 }
 169         }
 170         list_add_tail(&node->node_list, node_next);
 171
 172         plist_check_head(head);
 173 }
 174
 175 #ifdef CONFIG_DEBUG_PLIST
 176 #include <linux/sched.h>
 177 #include <linux/sched/clock.h>
 178 #include <linux/module.h>
 179 #include <linux/init.h>
 180
 181 static struct plist_node __initdata test_node[241];
 182
 183 static void __init plist_test_check(int nr_expect)
 184 {
 185         struct plist_node *first, *prio_pos, *node_pos;
 186
 187         if (plist_head_empty(&test_head)) {
 188                 BUG_ON(nr_expect != 0);
 189                 return;
 190         }
 191
 192         prio_pos = first = plist_first(&test_head);
 193         plist_for_each(node_pos, &test_head) {
 194                 if (nr_expect-- < 0)
 195                         break;
 196                 if (node_pos == first)
 197                         continue;
 198                 if (node_pos->prio == prio_pos->prio) {
 199                         BUG_ON(!list_empty(&node_pos->prio_list));
 200                         continue;
 201                 }
 202
 203                 BUG_ON(prio_pos->prio > node_pos->prio);
 204                 BUG_ON(prio_pos->prio_list.next != &node_pos->prio_list);
 205                 prio_pos = node_pos;
 206         }
 207
 208         BUG_ON(nr_expect != 0);
 209         BUG_ON(prio_pos->prio_list.next != &first->prio_list);
 210 }
 211
 212 static void __init plist_test_requeue(struct plist_node *node)
 213 {
 214         plist_requeue(node, &test_head);
 215
 216         if (node != plist_last(&test_head))
 217                 BUG_ON(node->prio == plist_next(node)->prio);
 218 }
 219
 220 static int  __init plist_test(void)
 221 {
 222         int nr_expect = 0, i, loop;
 223         unsigned int r = local_clock();
 224
 225         printk(KERN_DEBUG "start plist test\n");
 226         plist_head_init(&test_head);
 227         for (i = 0; i < ARRAY_SIZE(test_node); i++)
 228                 plist_node_init(test_node + i, 0);
 229
 230         for (loop = 0; loop < 1000; loop++) {
 231                 r = r * 193939 % 47629;
 232                 i = r % ARRAY_SIZE(test_node);
 233                 if (plist_node_empty(test_node + i)) {
 234                         r = r * 193939 % 47629;
 235                         test_node[i].prio = r % 99;
 236                         plist_add(test_node + i, &test_head);
 237                         nr_expect++;
 238                 } else {
 239                         plist_del(test_node + i, &test_head);
 240                         nr_expect--;
 241                 }
 242                 plist_test_check(nr_expect);
 243                 if (!plist_node_empty(test_node + i)) {
 244                         plist_test_requeue(test_node + i);
 245                         plist_test_check(nr_expect);
 246                 }
 247         }
 248
 249         for (i = 0; i < ARRAY_SIZE(test_node); i++) {
 250                 if (plist_node_empty(test_node + i))
 251                         continue;
 252                 plist_del(test_node + i, &test_head);
 253                 nr_expect--;
 254                 plist_test_check(nr_expect);
 255         }
 256
 257         printk(KERN_DEBUG "end plist test\n");
 258         return 0;
 259 }
 260
 261 module_init(plist_test);
 262
 263 #endif