dbus/list.h

   1 /* -*- Mode: C ; c-basic-offset: 2 -*- */
   2 /*****************************************************************************
   3  *
   4  *   Linux kernel header adapted for user-mode
   5  *   The 2.6.17-rt1 version was used.
   6  *
   7  *   Original copyright holders of this code are unknown, they were not
   8  *   mentioned in the original file.
   9  *
  10  *   This program is free software; you can redistribute it and/or modify
  11  *   it under the terms of the GNU General Public License as published by
  12  *   the Free Software Foundation; version 2 of the License
  13  *
  14  *   This program is distributed in the hope that it will be useful,
  15  *   but WITHOUT ANY WARRANTY; without even the implied warranty of
  16  *   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  17  *   GNU General Public License for more details.
  18  *
  19  *   You should have received a copy of the GNU General Public License
  20  *   along with this program; if not, write to the Free Software
  21  *   Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
  22  *
  23  *****************************************************************************/
  24
  25 #ifndef _LINUX_LIST_H
  26 #define _LINUX_LIST_H
  27
  28 #include <stddef.h>
  29
  30 #if !defined(offsetof)
  31 #define offsetof(TYPE, MEMBER) ((size_t) &((TYPE *)0)->MEMBER)
  32 #endif
  33
  34 /**
  35  * container_of - cast a member of a structure out to the containing structure
  36  * @ptr:        the pointer to the member.
  37  * @type:       the type of the container struct this is embedded in.
  38  * @member:     the name of the member within the struct.
  39  *
  40  */
  41 #define container_of(ptr, type, member) ({                      \
  42         const typeof( ((type *)0)->member ) *__mptr = (ptr);    \
  43         (type *)( (char *)__mptr - offsetof(type,member) );})
  44
  45 #define prefetch(x) (x = x)
  46
  47 /*
  48  * These are non-NULL pointers that will result in page faults
  49  * under normal circumstances, used to verify that nobody uses
  50  * non-initialized list entries.
  51  */
  52 #define LIST_POISON1  ((void *) 0x00100100)
  53 #define LIST_POISON2  ((void *) 0x00200200)
  54
  55 /*
  56  * Simple doubly linked list implementation.
  57  *
  58  * Some of the internal functions ("__xxx") are useful when
  59  * manipulating whole lists rather than single entries, as
  60  * sometimes we already know the next/prev entries and we can
  61  * generate better code by using them directly rather than
  62  * using the generic single-entry routines.
  63  */
  64
  65 struct list_head {
  66   struct list_head *next, *prev;
  67 };
  68
  69 #define LIST_HEAD_INIT(name) { &(name), &(name) }
  70
  71 #define LIST_HEAD(name) \
  72   struct list_head name = LIST_HEAD_INIT(name)
  73
  74 static inline void INIT_LIST_HEAD(struct list_head *list)
  75 {
  76   list->next = list;
  77   list->prev = list;
  78 }
  79
  80 /*
  81  * Insert a new entry between two known consecutive entries.
  82  *
  83  * This is only for internal list manipulation where we know
  84  * the prev/next entries already!
  85  */
  86 static inline void __list_add(struct list_head *new,
  87             struct list_head *prev,
  88             struct list_head *next)
  89 {
  90   next->prev = new;
  91   new->next = next;
  92   new->prev = prev;
  93   prev->next = new;
  94 }
  95
  96 /**
  97  * list_add - add a new entry
  98  * @new: new entry to be added
  99  * @head: list head to add it after
 100  *
 101  * Insert a new entry after the specified head.
 102  * This is good for implementing stacks.
 103  */
 104 static inline void list_add(struct list_head *new, struct list_head *head)
 105 {
 106   __list_add(new, head, head->next);
 107 }
 108
 109 /**
 110  * list_add_tail - add a new entry
 111  * @new: new entry to be added
 112  * @head: list head to add it before
 113  *
 114  * Insert a new entry before the specified head.
 115  * This is useful for implementing queues.
 116  */
 117 static inline void list_add_tail(struct list_head *new, struct list_head *head)
 118 {
 119   __list_add(new, head->prev, head);
 120 }
 121
 122 /*
 123  * Insert a new entry between two known consecutive entries.
 124  *
 125  * This is only for internal list manipulation where we know
 126  * the prev/next entries already!
 127  */
 128 static inline void __list_add_rcu(struct list_head * new,
 129     struct list_head * prev, struct list_head * next)
 130 {
 131   new->next = next;
 132   new->prev = prev;
 133 //  smp_wmb();
 134   next->prev = new;
 135   prev->next = new;
 136 }
 137
 138 /**
 139  * list_add_rcu - add a new entry to rcu-protected list
 140  * @new: new entry to be added
 141  * @head: list head to add it after
 142  *
 143  * Insert a new entry after the specified head.
 144  * This is good for implementing stacks.
 145  *
 146  * The caller must take whatever precautions are necessary
 147  * (such as holding appropriate locks) to avoid racing
 148  * with another list-mutation primitive, such as list_add_rcu()
 149  * or list_del_rcu(), running on this same list.
 150  * However, it is perfectly legal to run concurrently with
 151  * the _rcu list-traversal primitives, such as
 152  * list_for_each_entry_rcu().
 153  */
 154 static inline void list_add_rcu(struct list_head *new, struct list_head *head)
 155 {
 156   __list_add_rcu(new, head, head->next);
 157 }
 158
 159 /**
 160  * list_add_tail_rcu - add a new entry to rcu-protected list
 161  * @new: new entry to be added
 162  * @head: list head to add it before
 163  *
 164  * Insert a new entry before the specified head.
 165  * This is useful for implementing queues.
 166  *
 167  * The caller must take whatever precautions are necessary
 168  * (such as holding appropriate locks) to avoid racing
 169  * with another list-mutation primitive, such as list_add_tail_rcu()
 170  * or list_del_rcu(), running on this same list.
 171  * However, it is perfectly legal to run concurrently with
 172  * the _rcu list-traversal primitives, such as
 173  * list_for_each_entry_rcu().
 174  */
 175 static inline void list_add_tail_rcu(struct list_head *new,
 176           struct list_head *head)
 177 {
 178   __list_add_rcu(new, head->prev, head);
 179 }
 180
 181 /*
 182  * Delete a list entry by making the prev/next entries
 183  * point to each other.
 184  *
 185  * This is only for internal list manipulation where we know
 186  * the prev/next entries already!
 187  */
 188 static inline void __list_del(struct list_head * prev, struct list_head * next)
 189 {
 190   next->prev = prev;
 191   prev->next = next;
 192 }
 193
 194 /**
 195  * list_del - deletes entry from list.
 196  * @entry: the element to delete from the list.
 197  * Note: list_empty on entry does not return true after this, the entry is
 198  * in an undefined state.
 199  */
 200 static inline void list_del(struct list_head *entry)
 201 {
 202   __list_del(entry->prev, entry->next);
 203   entry->next = LIST_POISON1;
 204   entry->prev = LIST_POISON2;
 205 }
 206
 207 /**
 208  * list_del_rcu - deletes entry from list without re-initialization
 209  * @entry: the element to delete from the list.
 210  *
 211  * Note: list_empty on entry does not return true after this,
 212  * the entry is in an undefined state. It is useful for RCU based
 213  * lockfree traversal.
 214  *
 215  * In particular, it means that we can not poison the forward
 216  * pointers that may still be used for walking the list.
 217  *
 218  * The caller must take whatever precautions are necessary
 219  * (such as holding appropriate locks) to avoid racing
 220  * with another list-mutation primitive, such as list_del_rcu()
 221  * or list_add_rcu(), running on this same list.
 222  * However, it is perfectly legal to run concurrently with
 223  * the _rcu list-traversal primitives, such as
 224  * list_for_each_entry_rcu().
 225  *
 226  * Note that the caller is not permitted to immediately free
 227  * the newly deleted entry.  Instead, either synchronize_rcu()
 228  * or call_rcu() must be used to defer freeing until an RCU
 229  * grace period has elapsed.
 230  */
 231 static inline void list_del_rcu(struct list_head *entry)
 232 {
 233   __list_del(entry->prev, entry->next);
 234   entry->prev = LIST_POISON2;
 235 }
 236
 237 /*
 238  * list_replace_rcu - replace old entry by new one
 239  * @old : the element to be replaced
 240  * @new : the new element to insert
 241  *
 242  * The old entry will be replaced with the new entry atomically.
 243  */
 244 static inline void list_replace_rcu(struct list_head *old,
 245         struct list_head *new)
 246 {
 247   new->next = old->next;
 248   new->prev = old->prev;
 249 //  smp_wmb();
 250   new->next->prev = new;
 251   new->prev->next = new;
 252   old->prev = LIST_POISON2;
 253 }
 254
 255 /**
 256  * list_del_init - deletes entry from list and reinitialize it.
 257  * @entry: the element to delete from the list.
 258  */
 259 static inline void list_del_init(struct list_head *entry)
 260 {
 261   __list_del(entry->prev, entry->next);
 262   INIT_LIST_HEAD(entry);
 263 }
 264
 265 /**
 266  * list_move - delete from one list and add as another's head
 267  * @list: the entry to move
 268  * @head: the head that will precede our entry
 269  */
 270 static inline void list_move(struct list_head *list, struct list_head *head)
 271 {
 272         __list_del(list->prev, list->next);
 273         list_add(list, head);
 274 }
 275
 276 /**
 277  * list_move_tail - delete from one list and add as another's tail
 278  * @list: the entry to move
 279  * @head: the head that will follow our entry
 280  */
 281 static inline void list_move_tail(struct list_head *list,
 282           struct list_head *head)
 283 {
 284         __list_del(list->prev, list->next);
 285         list_add_tail(list, head);
 286 }
 287
 288 /**
 289  * list_empty - tests whether a list is empty
 290  * @head: the list to test.
 291  */
 292 static inline int list_empty(const struct list_head *head)
 293 {
 294   return head->next == head;
 295 }
 296
 297 /**
 298  * list_empty_careful - tests whether a list is
 299  * empty _and_ checks that no other CPU might be
 300  * in the process of still modifying either member
 301  *
 302  * NOTE: using list_empty_careful() without synchronization
 303  * can only be safe if the only activity that can happen
 304  * to the list entry is list_del_init(). Eg. it cannot be used
 305  * if another CPU could re-list_add() it.
 306  *
 307  * @head: the list to test.
 308  */
 309 static inline int list_empty_careful(const struct list_head *head)
 310 {
 311   struct list_head *next = head->next;
 312   return (next == head) && (next == head->prev);
 313 }
 314
 315 static inline void __list_splice(struct list_head *list,
 316          struct list_head *head)
 317 {
 318   struct list_head *first = list->next;
 319   struct list_head *last = list->prev;
 320   struct list_head *at = head->next;
 321
 322   first->prev = head;
 323   head->next = first;
 324
 325   last->next = at;
 326   at->prev = last;
 327 }
 328
 329 /**
 330  * list_splice - join two lists
 331  * @list: the new list to add.
 332  * @head: the place to add it in the first list.
 333  */
 334 static inline void list_splice(struct list_head *list, struct list_head *head)
 335 {
 336   if (!list_empty(list))
 337     __list_splice(list, head);
 338 }
 339
 340 /**
 341  * list_splice_init - join two lists and reinitialise the emptied list.
 342  * @list: the new list to add.
 343  * @head: the place to add it in the first list.
 344  *
 345  * The list at @list is reinitialised
 346  */
 347 static inline void list_splice_init(struct list_head *list,
 348             struct list_head *head)
 349 {
 350   if (!list_empty(list)) {
 351     __list_splice(list, head);
 352     INIT_LIST_HEAD(list);
 353   }
 354 }
 355
 356 /**
 357  * list_entry - get the struct for this entry
 358  * @ptr:  the &struct list_head pointer.
 359  * @type: the type of the struct this is embedded in.
 360  * @member: the name of the list_struct within the struct.
 361  */
 362 #define list_entry(ptr, type, member) \
 363   container_of(ptr, type, member)
 364
 365 /**
 366  * list_for_each  - iterate over a list
 367  * @pos:  the &struct list_head to use as a loop counter.
 368  * @head: the head for your list.
 369  */
 370 #define list_for_each(pos, head) \
 371   for (pos = (head)->next; prefetch(pos->next), pos != (head); \
 372           pos = pos->next)
 373
 374 /**
 375  * __list_for_each  - iterate over a list
 376  * @pos:  the &struct list_head to use as a loop counter.
 377  * @head: the head for your list.
 378  *
 379  * This variant differs from list_for_each() in that it's the
 380  * simplest possible list iteration code, no prefetching is done.
 381  * Use this for code that knows the list to be very short (empty
 382  * or 1 entry) most of the time.
 383  */
 384 #define __list_for_each(pos, head) \
 385   for (pos = (head)->next; pos != (head); pos = pos->next)
 386
 387 /**
 388  * list_for_each_prev - iterate over a list backwards
 389  * @pos:  the &struct list_head to use as a loop counter.
 390  * @head: the head for your list.
 391  */
 392 #define list_for_each_prev(pos, head) \
 393   for (pos = (head)->prev; prefetch(pos->prev), pos != (head); \
 394           pos = pos->prev)
 395
 396 /**
 397  * list_for_each_safe - iterate over a list safe against removal of list entry
 398  * @pos:  the &struct list_head to use as a loop counter.
 399  * @n:    another &struct list_head to use as temporary storage
 400  * @head: the head for your list.
 401  */
 402 #define list_for_each_safe(pos, n, head) \
 403   for (pos = (head)->next, n = pos->next; pos != (head); \
 404     pos = n, n = pos->next)
 405
 406 /**
 407  * list_for_each_entry  - iterate over list of given type
 408  * @pos:  the type * to use as a loop counter.
 409  * @head: the head for your list.
 410  * @member: the name of the list_struct within the struct.
 411  */
 412 #define list_for_each_entry(pos, head, member)        \
 413   for (pos = list_entry((head)->next, typeof(*pos), member);  \
 414        prefetch(pos->member.next), &pos->member != (head);  \
 415        pos = list_entry(pos->member.next, typeof(*pos), member))
 416
 417 /**
 418  * list_for_each_entry_reverse - iterate backwards over list of given type.
 419  * @pos:  the type * to use as a loop counter.
 420  * @head: the head for your list.
 421  * @member: the name of the list_struct within the struct.
 422  */
 423 #define list_for_each_entry_reverse(pos, head, member)      \
 424   for (pos = list_entry((head)->prev, typeof(*pos), member);  \
 425        prefetch(pos->member.prev), &pos->member != (head);  \
 426        pos = list_entry(pos->member.prev, typeof(*pos), member))
 427
 428 /**
 429  * list_prepare_entry - prepare a pos entry for use as a start point in
 430  *      list_for_each_entry_continue
 431  * @pos:  the type * to use as a start point
 432  * @head: the head of the list
 433  * @member: the name of the list_struct within the struct.
 434  */
 435 #define list_prepare_entry(pos, head, member) \
 436   ((pos) ? : list_entry(head, typeof(*pos), member))
 437
 438 /**
 439  * list_for_each_entry_continue - iterate over list of given type
 440  *      continuing after existing point
 441  * @pos:  the type * to use as a loop counter.
 442  * @head: the head for your list.
 443  * @member: the name of the list_struct within the struct.
 444  */
 445 #define list_for_each_entry_continue(pos, head, member)     \
 446   for (pos = list_entry(pos->member.next, typeof(*pos), member);  \
 447        prefetch(pos->member.next), &pos->member != (head);  \
 448        pos = list_entry(pos->member.next, typeof(*pos), member))
 449
 450 /**
 451  * list_for_each_entry_from - iterate over list of given type
 452  *      continuing from existing point
 453  * @pos:  the type * to use as a loop counter.
 454  * @head: the head for your list.
 455  * @member: the name of the list_struct within the struct.
 456  */
 457 #define list_for_each_entry_from(pos, head, member)       \
 458   for (; prefetch(pos->member.next), &pos->member != (head);  \
 459        pos = list_entry(pos->member.next, typeof(*pos), member))
 460
 461 /**
 462  * list_for_each_entry_safe - iterate over list of given type safe against removal of list entry
 463  * @pos:  the type * to use as a loop counter.
 464  * @n:    another type * to use as temporary storage
 465  * @head: the head for your list.
 466  * @member: the name of the list_struct within the struct.
 467  */
 468 #define list_for_each_entry_safe(pos, n, head, member)      \
 469   for (pos = list_entry((head)->next, typeof(*pos), member),  \
 470     n = list_entry(pos->member.next, typeof(*pos), member); \
 471        &pos->member != (head);          \
 472        pos = n, n = list_entry(n->member.next, typeof(*n), member))
 473
 474 /**
 475  * list_for_each_entry_safe_continue -  iterate over list of given type
 476  *      continuing after existing point safe against removal of list entry
 477  * @pos:  the type * to use as a loop counter.
 478  * @n:    another type * to use as temporary storage
 479  * @head: the head for your list.
 480  * @member: the name of the list_struct within the struct.
 481  */
 482 #define list_for_each_entry_safe_continue(pos, n, head, member)     \
 483   for (pos = list_entry(pos->member.next, typeof(*pos), member),    \
 484     n = list_entry(pos->member.next, typeof(*pos), member);   \
 485        &pos->member != (head);            \
 486        pos = n, n = list_entry(n->member.next, typeof(*n), member))
 487
 488 /**
 489  * list_for_each_entry_safe_from - iterate over list of given type
 490  *      from existing point safe against removal of list entry
 491  * @pos:  the type * to use as a loop counter.
 492  * @n:    another type * to use as temporary storage
 493  * @head: the head for your list.
 494  * @member: the name of the list_struct within the struct.
 495  */
 496 #define list_for_each_entry_safe_from(pos, n, head, member)       \
 497   for (n = list_entry(pos->member.next, typeof(*pos), member);    \
 498        &pos->member != (head);            \
 499        pos = n, n = list_entry(n->member.next, typeof(*n), member))
 500
 501 /**
 502  * list_for_each_entry_safe_reverse - iterate backwards over list of given type safe against
 503  *              removal of list entry
 504  * @pos:  the type * to use as a loop counter.
 505  * @n:    another type * to use as temporary storage
 506  * @head: the head for your list.
 507  * @member: the name of the list_struct within the struct.
 508  */
 509 #define list_for_each_entry_safe_reverse(pos, n, head, member)    \
 510   for (pos = list_entry((head)->prev, typeof(*pos), member),  \
 511     n = list_entry(pos->member.prev, typeof(*pos), member); \
 512        &pos->member != (head);          \
 513        pos = n, n = list_entry(n->member.prev, typeof(*n), member))
 514
 515 /**
 516  * list_for_each_rcu  - iterate over an rcu-protected list
 517  * @pos:  the &struct list_head to use as a loop counter.
 518  * @head: the head for your list.
 519  *
 520  * This list-traversal primitive may safely run concurrently with
 521  * the _rcu list-mutation primitives such as list_add_rcu()
 522  * as long as the traversal is guarded by rcu_read_lock().
 523  */
 524 #define list_for_each_rcu(pos, head) \
 525   for (pos = (head)->next; \
 526     prefetch(rcu_dereference(pos)->next), pos != (head); \
 527           pos = pos->next)
 528
 529 #define __list_for_each_rcu(pos, head) \
 530   for (pos = (head)->next; \
 531     rcu_dereference(pos) != (head); \
 532           pos = pos->next)
 533
 534 /**
 535  * list_for_each_safe_rcu - iterate over an rcu-protected list safe
 536  *          against removal of list entry
 537  * @pos:  the &struct list_head to use as a loop counter.
 538  * @n:    another &struct list_head to use as temporary storage
 539  * @head: the head for your list.
 540  *
 541  * This list-traversal primitive may safely run concurrently with
 542  * the _rcu list-mutation primitives such as list_add_rcu()
 543  * as long as the traversal is guarded by rcu_read_lock().
 544  */
 545 #define list_for_each_safe_rcu(pos, n, head) \
 546   for (pos = (head)->next; \
 547     n = rcu_dereference(pos)->next, pos != (head); \
 548     pos = n)
 549
 550 /**
 551  * list_for_each_entry_rcu  - iterate over rcu list of given type
 552  * @pos:  the type * to use as a loop counter.
 553  * @head: the head for your list.
 554  * @member: the name of the list_struct within the struct.
 555  *
 556  * This list-traversal primitive may safely run concurrently with
 557  * the _rcu list-mutation primitives such as list_add_rcu()
 558  * as long as the traversal is guarded by rcu_read_lock().
 559  */
 560 #define list_for_each_entry_rcu(pos, head, member) \
 561   for (pos = list_entry((head)->next, typeof(*pos), member); \
 562     prefetch(rcu_dereference(pos)->member.next), \
 563       &pos->member != (head); \
 564     pos = list_entry(pos->member.next, typeof(*pos), member))
 565
 566
 567 /**
 568  * list_for_each_continue_rcu - iterate over an rcu-protected list
 569  *      continuing after existing point.
 570  * @pos:  the &struct list_head to use as a loop counter.
 571  * @head: the head for your list.
 572  *
 573  * This list-traversal primitive may safely run concurrently with
 574  * the _rcu list-mutation primitives such as list_add_rcu()
 575  * as long as the traversal is guarded by rcu_read_lock().
 576  */
 577 #define list_for_each_continue_rcu(pos, head) \
 578   for ((pos) = (pos)->next; \
 579     prefetch(rcu_dereference((pos))->next), (pos) != (head); \
 580           (pos) = (pos)->next)
 581
 582 /*
 583  * Double linked lists with a single pointer list head.
 584  * Mostly useful for hash tables where the two pointer list head is
 585  * too wasteful.
 586  * You lose the ability to access the tail in O(1).
 587  */
 588
 589 struct hlist_head {
 590   struct hlist_node *first;
 591 };
 592
 593 struct hlist_node {
 594   struct hlist_node *next, **pprev;
 595 };
 596
 597 #define HLIST_HEAD_INIT { .first = NULL }
 598 #define HLIST_HEAD(name) struct hlist_head name = {  .first = NULL }
 599 #define INIT_HLIST_HEAD(ptr) ((ptr)->first = NULL)
 600 static inline void INIT_HLIST_NODE(struct hlist_node *h)
 601 {
 602   h->next = NULL;
 603   h->pprev = NULL;
 604 }
 605
 606 static inline int hlist_unhashed(const struct hlist_node *h)
 607 {
 608   return !h->pprev;
 609 }
 610
 611 static inline int hlist_empty(const struct hlist_head *h)
 612 {
 613   return !h->first;
 614 }
 615
 616 static inline void __hlist_del(struct hlist_node *n)
 617 {
 618   struct hlist_node *next = n->next;
 619   struct hlist_node **pprev = n->pprev;
 620   *pprev = next;
 621   if (next)
 622     next->pprev = pprev;
 623 }
 624
 625 static inline void hlist_del(struct hlist_node *n)
 626 {
 627   __hlist_del(n);
 628   n->next = LIST_POISON1;
 629   n->pprev = LIST_POISON2;
 630 }
 631
 632 /**
 633  * hlist_del_rcu - deletes entry from hash list without re-initialization
 634  * @n: the element to delete from the hash list.
 635  *
 636  * Note: list_unhashed() on entry does not return true after this,
 637  * the entry is in an undefined state. It is useful for RCU based
 638  * lockfree traversal.
 639  *
 640  * In particular, it means that we can not poison the forward
 641  * pointers that may still be used for walking the hash list.
 642  *
 643  * The caller must take whatever precautions are necessary
 644  * (such as holding appropriate locks) to avoid racing
 645  * with another list-mutation primitive, such as hlist_add_head_rcu()
 646  * or hlist_del_rcu(), running on this same list.
 647  * However, it is perfectly legal to run concurrently with
 648  * the _rcu list-traversal primitives, such as
 649  * hlist_for_each_entry().
 650  */
 651 static inline void hlist_del_rcu(struct hlist_node *n)
 652 {
 653   __hlist_del(n);
 654   n->pprev = LIST_POISON2;
 655 }
 656
 657 static inline void hlist_del_init(struct hlist_node *n)
 658 {
 659   if (!hlist_unhashed(n)) {
 660     __hlist_del(n);
 661     INIT_HLIST_NODE(n);
 662   }
 663 }
 664
 665 /*
 666  * hlist_replace_rcu - replace old entry by new one
 667  * @old : the element to be replaced
 668  * @new : the new element to insert
 669  *
 670  * The old entry will be replaced with the new entry atomically.
 671  */
 672 static inline void hlist_replace_rcu(struct hlist_node *old,
 673           struct hlist_node *new)
 674 {
 675   struct hlist_node *next = old->next;
 676
 677   new->next = next;
 678   new->pprev = old->pprev;
 679 //  smp_wmb();
 680   if (next)
 681     new->next->pprev = &new->next;
 682   *new->pprev = new;
 683   old->pprev = LIST_POISON2;
 684 }
 685
 686 static inline void hlist_add_head(struct hlist_node *n, struct hlist_head *h)
 687 {
 688   struct hlist_node *first = h->first;
 689   n->next = first;
 690   if (first)
 691     first->pprev = &n->next;
 692   h->first = n;
 693   n->pprev = &h->first;
 694 }
 695
 696
 697 /**
 698  * hlist_add_head_rcu - adds the specified element to the specified hlist,
 699  * while permitting racing traversals.
 700  * @n: the element to add to the hash list.
 701  * @h: the list to add to.
 702  *
 703  * The caller must take whatever precautions are necessary
 704  * (such as holding appropriate locks) to avoid racing
 705  * with another list-mutation primitive, such as hlist_add_head_rcu()
 706  * or hlist_del_rcu(), running on this same list.
 707  * However, it is perfectly legal to run concurrently with
 708  * the _rcu list-traversal primitives, such as
 709  * hlist_for_each_entry_rcu(), used to prevent memory-consistency
 710  * problems on Alpha CPUs.  Regardless of the type of CPU, the
 711  * list-traversal primitive must be guarded by rcu_read_lock().
 712  */
 713 static inline void hlist_add_head_rcu(struct hlist_node *n,
 714           struct hlist_head *h)
 715 {
 716   struct hlist_node *first = h->first;
 717   n->next = first;
 718   n->pprev = &h->first;
 719 //  smp_wmb();
 720   if (first)
 721     first->pprev = &n->next;
 722   h->first = n;
 723 }
 724
 725 /* next must be != NULL */
 726 static inline void hlist_add_before(struct hlist_node *n,
 727           struct hlist_node *next)
 728 {
 729   n->pprev = next->pprev;
 730   n->next = next;
 731   next->pprev = &n->next;
 732   *(n->pprev) = n;
 733 }
 734
 735 static inline void hlist_add_after(struct hlist_node *n,
 736           struct hlist_node *next)
 737 {
 738   next->next = n->next;
 739   n->next = next;
 740   next->pprev = &n->next;
 741
 742   if(next->next)
 743     next->next->pprev  = &next->next;
 744 }
 745
 746 /**
 747  * hlist_add_before_rcu - adds the specified element to the specified hlist
 748  * before the specified node while permitting racing traversals.
 749  * @n: the new element to add to the hash list.
 750  * @next: the existing element to add the new element before.
 751  *
 752  * The caller must take whatever precautions are necessary
 753  * (such as holding appropriate locks) to avoid racing
 754  * with another list-mutation primitive, such as hlist_add_head_rcu()
 755  * or hlist_del_rcu(), running on this same list.
 756  * However, it is perfectly legal to run concurrently with
 757  * the _rcu list-traversal primitives, such as
 758  * hlist_for_each_entry_rcu(), used to prevent memory-consistency
 759  * problems on Alpha CPUs.
 760  */
 761 static inline void hlist_add_before_rcu(struct hlist_node *n,
 762           struct hlist_node *next)
 763 {
 764   n->pprev = next->pprev;
 765   n->next = next;
 766 //  smp_wmb();
 767   next->pprev = &n->next;
 768   *(n->pprev) = n;
 769 }
 770
 771 /**
 772  * hlist_add_after_rcu - adds the specified element to the specified hlist
 773  * after the specified node while permitting racing traversals.
 774  * @prev: the existing element to add the new element after.
 775  * @n: the new element to add to the hash list.
 776  *
 777  * The caller must take whatever precautions are necessary
 778  * (such as holding appropriate locks) to avoid racing
 779  * with another list-mutation primitive, such as hlist_add_head_rcu()
 780  * or hlist_del_rcu(), running on this same list.
 781  * However, it is perfectly legal to run concurrently with
 782  * the _rcu list-traversal primitives, such as
 783  * hlist_for_each_entry_rcu(), used to prevent memory-consistency
 784  * problems on Alpha CPUs.
 785  */
 786 static inline void hlist_add_after_rcu(struct hlist_node *prev,
 787                struct hlist_node *n)
 788 {
 789   n->next = prev->next;
 790   n->pprev = &prev->next;
 791 //  smp_wmb();
 792   prev->next = n;
 793   if (n->next)
 794     n->next->pprev = &n->next;
 795 }
 796
 797 #define hlist_entry(ptr, type, member) container_of(ptr,type,member)
 798
 799 #define hlist_for_each(pos, head) \
 800   for (pos = (head)->first; pos && ({ prefetch(pos->next); 1; }); \
 801        pos = pos->next)
 802
 803 #define hlist_for_each_safe(pos, n, head) \
 804   for (pos = (head)->first; pos && ({ n = pos->next; 1; }); \
 805        pos = n)
 806
 807 /**
 808  * hlist_for_each_entry - iterate over list of given type
 809  * @tpos: the type * to use as a loop counter.
 810  * @pos:  the &struct hlist_node to use as a loop counter.
 811  * @head: the head for your list.
 812  * @member: the name of the hlist_node within the struct.
 813  */
 814 #define hlist_for_each_entry(tpos, pos, head, member)      \
 815   for (pos = (head)->first;          \
 816        pos && ({ prefetch(pos->next); 1;}) &&      \
 817     ({ tpos = hlist_entry(pos, typeof(*tpos), member); 1;}); \
 818        pos = pos->next)
 819
 820 /**
 821  * hlist_for_each_entry_continue - iterate over a hlist continuing after existing point
 822  * @tpos: the type * to use as a loop counter.
 823  * @pos:  the &struct hlist_node to use as a loop counter.
 824  * @member: the name of the hlist_node within the struct.
 825  */
 826 #define hlist_for_each_entry_continue(tpos, pos, member)     \
 827   for (pos = (pos)->next;            \
 828        pos && ({ prefetch(pos->next); 1;}) &&      \
 829     ({ tpos = hlist_entry(pos, typeof(*tpos), member); 1;}); \
 830        pos = pos->next)
 831
 832 /**
 833  * hlist_for_each_entry_from - iterate over a hlist continuing from existing point
 834  * @tpos: the type * to use as a loop counter.
 835  * @pos:  the &struct hlist_node to use as a loop counter.
 836  * @member: the name of the hlist_node within the struct.
 837  */
 838 #define hlist_for_each_entry_from(tpos, pos, member)       \
 839   for (; pos && ({ prefetch(pos->next); 1;}) &&      \
 840     ({ tpos = hlist_entry(pos, typeof(*tpos), member); 1;}); \
 841        pos = pos->next)
 842
 843 /**
 844  * hlist_for_each_entry_safe - iterate over list of given type safe against removal of list entry
 845  * @tpos: the type * to use as a loop counter.
 846  * @pos:  the &struct hlist_node to use as a loop counter.
 847  * @n:    another &struct hlist_node to use as temporary storage
 848  * @head: the head for your list.
 849  * @member: the name of the hlist_node within the struct.
 850  */
 851 #define hlist_for_each_entry_safe(tpos, pos, n, head, member)      \
 852   for (pos = (head)->first;          \
 853        pos && ({ n = pos->next; 1; }) &&         \
 854     ({ tpos = hlist_entry(pos, typeof(*tpos), member); 1;}); \
 855        pos = n)
 856
 857 /**
 858  * hlist_for_each_entry_rcu - iterate over rcu list of given type
 859  * @tpos: the type * to use as a loop counter.
 860  * @pos:  the &struct hlist_node to use as a loop counter.
 861  * @head: the head for your list.
 862  * @member: the name of the hlist_node within the struct.
 863  *
 864  * This list-traversal primitive may safely run concurrently with
 865  * the _rcu list-mutation primitives such as hlist_add_head_rcu()
 866  * as long as the traversal is guarded by rcu_read_lock().
 867  */
 868 #define hlist_for_each_entry_rcu(tpos, pos, head, member)    \
 869   for (pos = (head)->first;          \
 870        rcu_dereference(pos) && ({ prefetch(pos->next); 1;}) &&   \
 871     ({ tpos = hlist_entry(pos, typeof(*tpos), member); 1;}); \
 872        pos = pos->next)
 873
 874 #endif