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 WRITE_ONCE(prev, next); 51 WRITE_ONCE(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, *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); 110 ins_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 removed 120 * @head: &struct plist_head pointer - list head 121 */ 122 void 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 by 149 * plist_add(). It moves an entry already in the plist to 150 * after any other same-priority entries. 151 * 152 * @node: &struct plist_node pointer - entry to be moved 153 * @head: &struct plist_head pointer - list head 154 */ 155 void 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_PLIST 186 #include <linux/sched.h> 187 #include <linux/sched/clock.h> 188 #include <linux/module.h> 189 #include <linux/init.h> 190 191 static struct plist_node __initdata test_node[241]; 192 193 static 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 } 221 222 static 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 } 229 230 static 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 } 296 297 module_init(plist_test); 298 299 #endif 300