第三十二课 linux内核链表剖析
Posted 天道酬勤
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__builtin_prefetch是gcc扩展的，用来提高访问效率，需要硬件的支持。
在标准C语言中是不允许static inline联合使用的。
删除依赖的头文件，将相应的结构拷贝到LinuxList.h中：
此外，需要将container_of改写成我们自己的形式。
1 #define container_of(ptr, type, member) ((type *)((char *)ptr - offsetof(type,member)))
移植后的内核链表如下：
1 #ifndef _LINUX_LIST_H 2 #define _LINUX_LIST_H 3 4 // #include <linux/types.h> 5 // #include <linux/stddef.h> 6 // #include <linux/poison.h> 7 // #include <linux/prefetch.h> 8 9 #ifndef offsetof 10 #define offsetof(TYPE, MEMBER) ((size_t) &((TYPE *)0)->MEMBER) 11 #endif 12 13 #ifndef container_of 14 #define container_of(ptr, type, member) ((type *)((char *)ptr - offsetof(type,member))) 15 #endif 16 17 #define prefetch(x) ((void)x) 18 19 #define LIST_POISON1 (NULL) 20 #define LIST_POISON2 (NULL) 21 22 struct list_head { 23 struct list_head *next, *prev; 24 }; 25 26 struct hlist_head { 27 struct hlist_node *first; 28 }; 29 30 struct hlist_node { 31 struct hlist_node *next, **pprev; 32 }; 33 34 /* 35 * Simple doubly linked list implementation. 36 * 37 * Some of the internal functions ("__xxx") are useful when 38 * manipulating whole lists rather than single entries, as 39 * sometimes we already know the next/prev entries and we can 40 * generate better code by using them directly rather than 41 * using the generic single-entry routines. 42 */ 43 44 #define LIST_HEAD_INIT(name) { &(name), &(name) } 45 46 #define LIST_HEAD(name) \\ 47 struct list_head name = LIST_HEAD_INIT(name) 48 49 static void INIT_LIST_HEAD(struct list_head *list) 50 { 51 list->next = list; 52 list->prev = list; 53 } 54 55 /* 56 * Insert a new entry between two known consecutive entries. 57 * 58 * This is only for internal list manipulation where we know 59 * the prev/next entries already! 60 */ 61 #ifndef CONFIG_DEBUG_LIST 62 static void __list_add(struct list_head *new, 63 struct list_head *prev, 64 struct list_head *next) 65 { 66 next->prev = new; 67 new->next = next; 68 new->prev = prev; 69 prev->next = new; 70 } 71 #else 72 extern void __list_add(struct list_head *new, 73 struct list_head *prev, 74 struct list_head *next); 75 #endif 76 77 /** 78 * list_add - add a new entry 79 * @new: new entry to be added 80 * @head: list head to add it after 81 * 82 * Insert a new entry after the specified head. 83 * This is good for implementing stacks. 84 */ 85 static void list_add(struct list_head *new, struct list_head *head) 86 { 87 __list_add(new, head, head->next); 88 } 89 90 91 /** 92 * list_add_tail - add a new entry 93 * @new: new entry to be added 94 * @head: list head to add it before 95 * 96 * Insert a new entry before the specified head. 97 * This is useful for implementing queues. 98 */ 99 static void list_add_tail(struct list_head *new, struct list_head *head) 100 { 101 __list_add(new, head->prev, head); 102 } 103 104 /* 105 * Delete a list entry by making the prev/next entries 106 * point to each other. 107 * 108 * This is only for internal list manipulation where we know 109 * the prev/next entries already! 110 */ 111 static void __list_del(struct list_head * prev, struct list_head * next) 112 { 113 next->prev = prev; 114 prev->next = next; 115 } 116 117 /** 118 * list_del - deletes entry from list. 119 * @entry: the element to delete from the list. 120 * Note: list_empty() on entry does not return true after this, the entry is 121 * in an undefined state. 122 */ 123 #ifndef CONFIG_DEBUG_LIST 124 static void __list_del_entry(struct list_head *entry) 125 { 126 __list_del(entry->prev, entry->next); 127 } 128 129 static void list_del(struct list_head *entry) 130 { 131 __list_del(entry->prev, entry->next); 132 entry->next = LIST_POISON1; 133 entry->prev = LIST_POISON2; 134 } 135 #else 136 extern void __list_del_entry(struct list_head *entry); 137 extern void list_del(struct list_head *entry); 138 #endif 139 140 /** 141 * list_replace - replace old entry by new one 142 * @old : the element to be replaced 143 * @new : the new element to insert 144 * 145 * If @old was empty, it will be overwritten. 146 */ 147 static void list_replace(struct list_head *old, 148 struct list_head *new) 149 { 150 new->next = old->next; 151 new->next->prev = new; 152 new->prev = old->prev; 153 new->prev->next = new; 154 } 155 156 static void list_replace_init(struct list_head *old, 157 struct list_head *new) 158 { 159 list_replace(old, new); 160 INIT_LIST_HEAD(old); 161 } 162 163 /** 164 * list_del_init - deletes entry from list and reinitialize it. 165 * @entry: the element to delete from the list. 166 */ 167 static void list_del_init(struct list_head *entry) 168 { 169 __list_del_entry(entry); 170 INIT_LIST_HEAD(entry); 171 } 172 173 /** 174 * list_move - delete from one list and add as another\'s head 175 * @list: the entry to move 176 * @head: the head that will precede our entry 177 */ 178 static void list_move(struct list_head *list, struct list_head *head) 179 { 180 __list_del_entry(list); 181 list_add(list, head); 182 } 183 184 /** 185 * list_move_tail - delete from one list and add as another\'s tail 186 * @list: the entry to move 187 * @head: the head that will follow our entry 188 */ 189 static void list_move_tail(struct list_head *list, 190 struct list_head *head) 191 { 192 __list_del_entry(list); 193 list_add_tail(list, head); 194 } 195 196 /** 197 * list_is_last - tests whether @list is the last entry in list @head 198 * @list: the entry to test 199 * @head: the head of the list 200 */ 201 static int list_is_last(const struct list_head *list, 202 const struct list_head *head) 203 { 204 return list->next == head; 205 } 206 207 /** 208 * list_empty - tests whether a list is empty 209 * @head: the list to test. 210 */ 211 static int list_empty(const struct list_head *head) 212 { 213 return head->next == head; 214 } 215 216 /** 217 * list_empty_careful - tests whether a list is empty and not being modified 218 * @head: the list to test 219 * 220 * Description: 221 * tests whether a list is empty _and_ checks that no other CPU might be 222 * in the process of modifying either member (next or prev) 223 * 224 * NOTE: using list_empty_careful() without synchronization 225 * can only be safe if the only activity that can happen 226 * to the list entry is list_del_init(). Eg. it cannot be used 227 * if another CPU could re-list_add() it. 228 */ 229 static int list_empty_careful(const struct list_head *head) 230 { 231 struct list_head *next = head->next; 232 return (next == head) && (next == head->prev); 233 } 234 235 /** 236 * list_rotate_left - rotate the list to the left 237 * @head: the head of the list 238 */ 239 static void list_rotate_left(struct list_head *head) 240 { 241 struct list_head *first; 242 243 if (!list_empty(head)) { 244 first = head->next; 245 list_move_tail(first, head); 246 } 247 } 248 249 /** 250 * list_is_singular - tests whether a list has just one entry. 251 * @head: the list to test. 252 */ 253 static int list_is_singular(const struct list_head *head) 254 { 255 return !list_empty(head) && (head->next == head->prev); 256 } 257 258 static void __list_cut_position(struct list_head *list, 259 struct list_head *head, struct list_head *entry) 260 { 261 struct list_head *new_first = entry->next; 262 list->next = head->next; 263 list->next->prev = list; 264 list->prev = entry; 265 entry->next = list; 266 head->next = new_first; 267 new_first->prev = head; 268 } 269 270 /** 271 * list_cut_position - cut a list into two 272 * @list: a new list to add all removed entries 273 * @head: a list with entries 274 * @entry: an entry within head, could be the head itself 275 * and if so we won\'t cut the list 276 * 277 * This helper moves the initial part of @head, up to and 278 * including @entry, from @head to @list. You should 279 * pass on @entry an element you know is on @head. @list 280 * should be an empty list or a list you do not care about 281 * losing its data. 282 * 283 */ 284 static void list_cut_position(struct list_head *list, 285 struct list_head *head, struct list_head *entry) 286 { 287 if (list_empty(head)) 288 return; 289 if (list_is_singular(head) && 290 (head->next != entry && head != entry)) 291 return; 292 if (entry == head) 293 INIT_LIST_HEAD(list); 294 else 295 __list_cut_position(list, head, entry); 296 } 297 298 static void __list_splice(const struct list_head *list, 299 struct list_head *prev, 300 struct list_head *next) 301 { 302 struct list_head *first = list->next; 303 struct list_head *last = list->prev; 304 305 first->prev = prev; 306 prev->next = first; 307 308 last->next = next; 309 next->prev = last; 310 } 311 312 /** 313 * list_splice - join two lists, this is designed for stacks 314 * @list: the new list to add. 315 * @head: the place to add it in the first list. 316 */ 317 static void list_splice(const struct list_head *list, 318 struct list_head *head) 319 { 320 if (!list_empty(list)) 321 __list_splice(list, head, head->next); 322 } 323 324 /** 325 * list_splice_tail - join two lists, each list being a queue 326 * @list: the new list to add. 327 * @head: the place to add it in the first list. 328 */ 329 static void list_splice_tail(struct list_head *list, 330 struct list_head *head) 331 { 332 if (!list_empty(list)) 333 __list_splice(list, head->prev, head); 334 } 335 336 /** 337 * list_splice_init - join two lists and reinitialise the emptied list. 338 * @list: the new list to add. 339 * @head: the place to add it in the first list. 340 * 341 * The list at @list is reinitialised 342 */ 343 static void list_splice_init(struct list_head *list, 344 struct list_head *head) 345 { 346 if (!list_empty(list)) { 347 __list_splice(list, head, head->next); 348 INIT_LIST_HEAD(list); 349 } 350 } 351 352 /** 353 * list_splice_tail_init - join two lists and reinitialise the emptied list 354 * @list: the new list to add. 355 * @head: the place to add it in the first list. 356 * 357 * Each of the lists is a queue. 358 * The list at @list is reinitialised 359 */ 360 static void list_splice_tail_init(struct list_head *list, 361 struct list_head *head) 362 { 363 if (!list_empty(list)) { 364 __list_splice(list, head->prev, head); 365 INIT_LIST_HEAD(list); 366 } 367 } 368 369 /** 370 * list_entry - get the struct for this entry 371 * @ptr: the &struct list_head pointer. 372 * @type: the type of the struct this is embedded in. 373 * @member: the name of the list_struct within the struct. 374 */ 375 #define list_entry(ptr, type, member) \\ 376 container_of(ptr, type, member) 377 378 /** 379 * list_first_entry - get the first element from a list 380 * @ptr: the list head to take the element from. 381 * @type: the type of the struct this is embedded in. 382 * @member: the name of the list_struct within the struct. 383 * 384 * Note, that list is expected to be not empty. 385 */ 386 #define list_first_entry(ptr, type, member) \\ 387 list_entry((ptr)->next, type, member) 388 389 /** 390 * list_for_each - iterate over a list 391 * @pos: the &struct list_head to use as a loop cursor. 392 * @head: the head for your list. 393 */ 394 #define list_for_each(pos, head) \\ 395 for (pos = (head)->next; prefetch(pos->next), pos != (head); \\ 396 pos = pos->next) 397 398 /** 399 * __list_for_each - iterate over a list 400 * @pos: the &struct list_head to use as a loop cursor. 401 * @head: the head for your list. 402 * 403 * This variant differs from list_for_each() in that it\'s the 404 * simplest possible list iteration code, no prefetching is done. 405 * Use this for code that knows the list to be very short (empty 406 * or 1 entry) most of the time. 407 */ 408 #define __list_for_each(pos, head) \\ 409 for (pos = (head)->next; pos != (head); pos = pos->next) 410 411 /** 412 * list_for_each_prev - iterate over a list backwards 413 * @pos: the &struct list_head to use as a loop cursor. 414 * @head: the head for your list. 415 */ 416 #define list_for_each_prev(pos, head) \\ 417 for (pos = (head)->prev; prefetch(pos->prev), pos != (head); \\ 418 pos = pos->prev) 419 420 /** 421 * list_for_each_safe - iterate over a list safe against removal of list entry 422 * @pos: the &struct list_head to use as a loop cursor. 423 * @n: another &struct list_head to use as temporary storage 424 * @head: the head for your list. 425 */ 426 #define list_for_each_safe(pos, n, head) \\ 427 for (pos = (head)->next, n = pos->next; pos != (head); \\ 428 pos = n, n = pos->next) 429 430 /** 431 * list_for_each_prev_safe - iterate over a list backwards safe against removal of list entry 432 * @pos: the &struct list_head to use as a loop cursor. 433 * @n: another &struct list_head to use as temporary storage 434 * @head: the head for your list. 435 */ 436 #define list_for_each_prev_safe(pos, n, head) \\ 437 for (pos = (head)->prev, n = pos->prev; \\ 438 prefetch(pos->prev), pos != (head); \\ 439 pos = n, n = pos->prev) 440 441 /** 442 * list_for_each_entry - iterate over list of given type 443 * @pos: the type * to use as a loop cursor. 444 * @head: the head for your list. 445 * @member: the name of the list_struct within the struct. 446 */ 447 #define list_for_each_entry(pos, head, member) \\ 448 for (pos = list_entry((head)->next, typeof(*pos), member); \\ 449 prefetch(pos->member.next), &pos->member != (head); \\ 以上是关于第三十二课 linux内核链表剖析的主要内容，如果未能解决你的问题，请参考以下文章