LCOV - code coverage report
Current view: top level - include/linux - rculist.h (source / functions) Hit Total Coverage
Test: combined.info Lines: 51 69 73.9 %
Date: 2022-03-28 13:20:08 Functions: 0 0 -
Branches: 32 124 25.8 %

           Branch data     Line data    Source code
       1                 :            : /* SPDX-License-Identifier: GPL-2.0 */
       2                 :            : #ifndef _LINUX_RCULIST_H
       3                 :            : #define _LINUX_RCULIST_H
       4                 :            : 
       5                 :            : #ifdef __KERNEL__
       6                 :            : 
       7                 :            : /*
       8                 :            :  * RCU-protected list version
       9                 :            :  */
      10                 :            : #include <linux/list.h>
      11                 :            : #include <linux/rcupdate.h>
      12                 :            : 
      13                 :            : /*
      14                 :            :  * Why is there no list_empty_rcu()?  Because list_empty() serves this
      15                 :            :  * purpose.  The list_empty() function fetches the RCU-protected pointer
      16                 :            :  * and compares it to the address of the list head, but neither dereferences
      17                 :            :  * this pointer itself nor provides this pointer to the caller.  Therefore,
      18                 :            :  * it is not necessary to use rcu_dereference(), so that list_empty() can
      19                 :            :  * be used anywhere you would want to use a list_empty_rcu().
      20                 :            :  */
      21                 :            : 
      22                 :            : /*
      23                 :            :  * INIT_LIST_HEAD_RCU - Initialize a list_head visible to RCU readers
      24                 :            :  * @list: list to be initialized
      25                 :            :  *
      26                 :            :  * You should instead use INIT_LIST_HEAD() for normal initialization and
      27                 :            :  * cleanup tasks, when readers have no access to the list being initialized.
      28                 :            :  * However, if the list being initialized is visible to readers, you
      29                 :            :  * need to keep the compiler from being too mischievous.
      30                 :            :  */
      31                 :       1740 : static inline void INIT_LIST_HEAD_RCU(struct list_head *list)
      32                 :            : {
      33                 :       1740 :         WRITE_ONCE(list->next, list);
      34                 :       1740 :         WRITE_ONCE(list->prev, list);
      35                 :            : }
      36                 :            : 
      37                 :            : /*
      38                 :            :  * return the ->next pointer of a list_head in an rcu safe
      39                 :            :  * way, we must not access it directly
      40                 :            :  */
      41                 :            : #define list_next_rcu(list)     (*((struct list_head __rcu **)(&(list)->next)))
      42                 :            : 
      43                 :            : /**
      44                 :            :  * list_tail_rcu - returns the prev pointer of the head of the list
      45                 :            :  * @head: the head of the list
      46                 :            :  *
      47                 :            :  * Note: This should only be used with the list header, and even then
      48                 :            :  * only if list_del() and similar primitives are not also used on the
      49                 :            :  * list header.
      50                 :            :  */
      51                 :            : #define list_tail_rcu(head)     (*((struct list_head __rcu **)(&(head)->prev)))
      52                 :            : 
      53                 :            : /*
      54                 :            :  * Check during list traversal that we are within an RCU reader
      55                 :            :  */
      56                 :            : 
      57                 :            : #define check_arg_count_one(dummy)
      58                 :            : 
      59                 :            : #ifdef CONFIG_PROVE_RCU_LIST
      60                 :            : #define __list_check_rcu(dummy, cond, extra...)                         \
      61                 :            :         ({                                                              \
      62                 :            :         check_arg_count_one(extra);                                     \
      63                 :            :         RCU_LOCKDEP_WARN(!cond && !rcu_read_lock_any_held(),            \
      64                 :            :                          "RCU-list traversed in non-reader section!");        \
      65                 :            :          })
      66                 :            : #else
      67                 :            : #define __list_check_rcu(dummy, cond, extra...)                         \
      68                 :            :         ({ check_arg_count_one(extra); })
      69                 :            : #endif
      70                 :            : 
      71                 :            : /*
      72                 :            :  * Insert a new entry between two known consecutive entries.
      73                 :            :  *
      74                 :            :  * This is only for internal list manipulation where we know
      75                 :            :  * the prev/next entries already!
      76                 :            :  */
      77                 :      28467 : static inline void __list_add_rcu(struct list_head *new,
      78                 :            :                 struct list_head *prev, struct list_head *next)
      79                 :            : {
      80                 :      28467 :         if (!__list_add_valid(new, prev, next))
      81                 :            :                 return;
      82                 :            : 
      83                 :      28467 :         new->next = next;
      84                 :      14394 :         new->prev = prev;
      85         [ +  + ]:      28347 :         rcu_assign_pointer(list_next_rcu(prev), new);
      86         [ +  + ]:      26361 :         next->prev = new;
      87                 :            : }
      88                 :            : 
      89                 :            : /**
      90                 :            :  * list_add_rcu - add a new entry to rcu-protected list
      91                 :            :  * @new: new entry to be added
      92                 :            :  * @head: list head to add it after
      93                 :            :  *
      94                 :            :  * Insert a new entry after the specified head.
      95                 :            :  * This is good for implementing stacks.
      96                 :            :  *
      97                 :            :  * The caller must take whatever precautions are necessary
      98                 :            :  * (such as holding appropriate locks) to avoid racing
      99                 :            :  * with another list-mutation primitive, such as list_add_rcu()
     100                 :            :  * or list_del_rcu(), running on this same list.
     101                 :            :  * However, it is perfectly legal to run concurrently with
     102                 :            :  * the _rcu list-traversal primitives, such as
     103                 :            :  * list_for_each_entry_rcu().
     104                 :            :  */
     105                 :       2748 : static inline void list_add_rcu(struct list_head *new, struct list_head *head)
     106                 :            : {
     107                 :       2748 :         __list_add_rcu(new, head, head->next);
     108                 :       1536 : }
     109                 :            : 
     110                 :            : /**
     111                 :            :  * list_add_tail_rcu - add a new entry to rcu-protected list
     112                 :            :  * @new: new entry to be added
     113                 :            :  * @head: list head to add it before
     114                 :            :  *
     115                 :            :  * Insert a new entry before the specified head.
     116                 :            :  * This is useful for implementing queues.
     117                 :            :  *
     118                 :            :  * The caller must take whatever precautions are necessary
     119                 :            :  * (such as holding appropriate locks) to avoid racing
     120                 :            :  * with another list-mutation primitive, such as list_add_tail_rcu()
     121                 :            :  * or list_del_rcu(), running on this same list.
     122                 :            :  * However, it is perfectly legal to run concurrently with
     123                 :            :  * the _rcu list-traversal primitives, such as
     124                 :            :  * list_for_each_entry_rcu().
     125                 :            :  */
     126                 :      25719 : static inline void list_add_tail_rcu(struct list_head *new,
     127                 :            :                                         struct list_head *head)
     128                 :            : {
     129                 :      25599 :         __list_add_rcu(new, head->prev, head);
     130                 :        870 : }
     131                 :            : 
     132                 :            : /**
     133                 :            :  * list_del_rcu - deletes entry from list without re-initialization
     134                 :            :  * @entry: the element to delete from the list.
     135                 :            :  *
     136                 :            :  * Note: list_empty() on entry does not return true after this,
     137                 :            :  * the entry is in an undefined state. It is useful for RCU based
     138                 :            :  * lockfree traversal.
     139                 :            :  *
     140                 :            :  * In particular, it means that we can not poison the forward
     141                 :            :  * pointers that may still be used for walking the list.
     142                 :            :  *
     143                 :            :  * The caller must take whatever precautions are necessary
     144                 :            :  * (such as holding appropriate locks) to avoid racing
     145                 :            :  * with another list-mutation primitive, such as list_del_rcu()
     146                 :            :  * or list_add_rcu(), running on this same list.
     147                 :            :  * However, it is perfectly legal to run concurrently with
     148                 :            :  * the _rcu list-traversal primitives, such as
     149                 :            :  * list_for_each_entry_rcu().
     150                 :            :  *
     151                 :            :  * Note that the caller is not permitted to immediately free
     152                 :            :  * the newly deleted entry.  Instead, either synchronize_rcu()
     153                 :            :  * or call_rcu() must be used to defer freeing until an RCU
     154                 :            :  * grace period has elapsed.
     155                 :            :  */
     156                 :      29040 : static inline void list_del_rcu(struct list_head *entry)
     157                 :            : {
     158   [ -  +  #  # ]:      16890 :         __list_del_entry(entry);
     159   [ -  +  #  # ]:      16890 :         entry->prev = LIST_POISON2;
     160                 :          0 : }
     161                 :            : 
     162                 :            : /**
     163                 :            :  * hlist_del_init_rcu - deletes entry from hash list with re-initialization
     164                 :            :  * @n: the element to delete from the hash list.
     165                 :            :  *
     166                 :            :  * Note: list_unhashed() on the node return true after this. It is
     167                 :            :  * useful for RCU based read lockfree traversal if the writer side
     168                 :            :  * must know if the list entry is still hashed or already unhashed.
     169                 :            :  *
     170                 :            :  * In particular, it means that we can not poison the forward pointers
     171                 :            :  * that may still be used for walking the hash list and we can only
     172                 :            :  * zero the pprev pointer so list_unhashed() will return true after
     173                 :            :  * this.
     174                 :            :  *
     175                 :            :  * The caller must take whatever precautions are necessary (such as
     176                 :            :  * holding appropriate locks) to avoid racing with another
     177                 :            :  * list-mutation primitive, such as hlist_add_head_rcu() or
     178                 :            :  * hlist_del_rcu(), running on this same list.  However, it is
     179                 :            :  * perfectly legal to run concurrently with the _rcu list-traversal
     180                 :            :  * primitives, such as hlist_for_each_entry_rcu().
     181                 :            :  */
     182                 :       3539 : static inline void hlist_del_init_rcu(struct hlist_node *n)
     183                 :            : {
     184   [ +  -  +  -  :       3539 :         if (!hlist_unhashed(n)) {
                   #  # ]
     185   [ +  +  +  +  :       3539 :                 __hlist_del(n);
                   #  # ]
     186                 :       3539 :                 WRITE_ONCE(n->pprev, NULL);
     187                 :            :         }
     188                 :            : }
     189                 :            : 
     190                 :            : /**
     191                 :            :  * list_replace_rcu - replace old entry by new one
     192                 :            :  * @old : the element to be replaced
     193                 :            :  * @new : the new element to insert
     194                 :            :  *
     195                 :            :  * The @old entry will be replaced with the @new entry atomically.
     196                 :            :  * Note: @old should not be empty.
     197                 :            :  */
     198                 :          0 : static inline void list_replace_rcu(struct list_head *old,
     199                 :            :                                 struct list_head *new)
     200                 :            : {
     201                 :          0 :         new->next = old->next;
     202                 :          0 :         new->prev = old->prev;
     203         [ #  # ]:          0 :         rcu_assign_pointer(list_next_rcu(new->prev), new);
     204                 :          0 :         new->next->prev = new;
     205         [ #  # ]:          0 :         old->prev = LIST_POISON2;
     206                 :            : }
     207                 :            : 
     208                 :            : /**
     209                 :            :  * __list_splice_init_rcu - join an RCU-protected list into an existing list.
     210                 :            :  * @list:       the RCU-protected list to splice
     211                 :            :  * @prev:       points to the last element of the existing list
     212                 :            :  * @next:       points to the first element of the existing list
     213                 :            :  * @sync:       synchronize_rcu, synchronize_rcu_expedited, ...
     214                 :            :  *
     215                 :            :  * The list pointed to by @prev and @next can be RCU-read traversed
     216                 :            :  * concurrently with this function.
     217                 :            :  *
     218                 :            :  * Note that this function blocks.
     219                 :            :  *
     220                 :            :  * Important note: the caller must take whatever action is necessary to prevent
     221                 :            :  * any other updates to the existing list.  In principle, it is possible to
     222                 :            :  * modify the list as soon as sync() begins execution. If this sort of thing
     223                 :            :  * becomes necessary, an alternative version based on call_rcu() could be
     224                 :            :  * created.  But only if -really- needed -- there is no shortage of RCU API
     225                 :            :  * members.
     226                 :            :  */
     227                 :            : static inline void __list_splice_init_rcu(struct list_head *list,
     228                 :            :                                           struct list_head *prev,
     229                 :            :                                           struct list_head *next,
     230                 :            :                                           void (*sync)(void))
     231                 :            : {
     232                 :            :         struct list_head *first = list->next;
     233                 :            :         struct list_head *last = list->prev;
     234                 :            : 
     235                 :            :         /*
     236                 :            :          * "first" and "last" tracking list, so initialize it.  RCU readers
     237                 :            :          * have access to this list, so we must use INIT_LIST_HEAD_RCU()
     238                 :            :          * instead of INIT_LIST_HEAD().
     239                 :            :          */
     240                 :            : 
     241                 :            :         INIT_LIST_HEAD_RCU(list);
     242                 :            : 
     243                 :            :         /*
     244                 :            :          * At this point, the list body still points to the source list.
     245                 :            :          * Wait for any readers to finish using the list before splicing
     246                 :            :          * the list body into the new list.  Any new readers will see
     247                 :            :          * an empty list.
     248                 :            :          */
     249                 :            : 
     250                 :            :         sync();
     251                 :            : 
     252                 :            :         /*
     253                 :            :          * Readers are finished with the source list, so perform splice.
     254                 :            :          * The order is important if the new list is global and accessible
     255                 :            :          * to concurrent RCU readers.  Note that RCU readers are not
     256                 :            :          * permitted to traverse the prev pointers without excluding
     257                 :            :          * this function.
     258                 :            :          */
     259                 :            : 
     260                 :            :         last->next = next;
     261                 :            :         rcu_assign_pointer(list_next_rcu(prev), first);
     262                 :            :         first->prev = prev;
     263                 :            :         next->prev = last;
     264                 :            : }
     265                 :            : 
     266                 :            : /**
     267                 :            :  * list_splice_init_rcu - splice an RCU-protected list into an existing list,
     268                 :            :  *                        designed for stacks.
     269                 :            :  * @list:       the RCU-protected list to splice
     270                 :            :  * @head:       the place in the existing list to splice the first list into
     271                 :            :  * @sync:       synchronize_rcu, synchronize_rcu_expedited, ...
     272                 :            :  */
     273                 :            : static inline void list_splice_init_rcu(struct list_head *list,
     274                 :            :                                         struct list_head *head,
     275                 :            :                                         void (*sync)(void))
     276                 :            : {
     277                 :            :         if (!list_empty(list))
     278                 :            :                 __list_splice_init_rcu(list, head, head->next, sync);
     279                 :            : }
     280                 :            : 
     281                 :            : /**
     282                 :            :  * list_splice_tail_init_rcu - splice an RCU-protected list into an existing
     283                 :            :  *                             list, designed for queues.
     284                 :            :  * @list:       the RCU-protected list to splice
     285                 :            :  * @head:       the place in the existing list to splice the first list into
     286                 :            :  * @sync:       synchronize_rcu, synchronize_rcu_expedited, ...
     287                 :            :  */
     288                 :            : static inline void list_splice_tail_init_rcu(struct list_head *list,
     289                 :            :                                              struct list_head *head,
     290                 :            :                                              void (*sync)(void))
     291                 :            : {
     292                 :            :         if (!list_empty(list))
     293                 :            :                 __list_splice_init_rcu(list, head->prev, head, sync);
     294                 :            : }
     295                 :            : 
     296                 :            : /**
     297                 :            :  * list_entry_rcu - get the struct for this entry
     298                 :            :  * @ptr:        the &struct list_head pointer.
     299                 :            :  * @type:       the type of the struct this is embedded in.
     300                 :            :  * @member:     the name of the list_head within the struct.
     301                 :            :  *
     302                 :            :  * This primitive may safely run concurrently with the _rcu list-mutation
     303                 :            :  * primitives such as list_add_rcu() as long as it's guarded by rcu_read_lock().
     304                 :            :  */
     305                 :            : #define list_entry_rcu(ptr, type, member) \
     306                 :            :         container_of(READ_ONCE(ptr), type, member)
     307                 :            : 
     308                 :            : /*
     309                 :            :  * Where are list_empty_rcu() and list_first_entry_rcu()?
     310                 :            :  *
     311                 :            :  * Implementing those functions following their counterparts list_empty() and
     312                 :            :  * list_first_entry() is not advisable because they lead to subtle race
     313                 :            :  * conditions as the following snippet shows:
     314                 :            :  *
     315                 :            :  * if (!list_empty_rcu(mylist)) {
     316                 :            :  *      struct foo *bar = list_first_entry_rcu(mylist, struct foo, list_member);
     317                 :            :  *      do_something(bar);
     318                 :            :  * }
     319                 :            :  *
     320                 :            :  * The list may not be empty when list_empty_rcu checks it, but it may be when
     321                 :            :  * list_first_entry_rcu rereads the ->next pointer.
     322                 :            :  *
     323                 :            :  * Rereading the ->next pointer is not a problem for list_empty() and
     324                 :            :  * list_first_entry() because they would be protected by a lock that blocks
     325                 :            :  * writers.
     326                 :            :  *
     327                 :            :  * See list_first_or_null_rcu for an alternative.
     328                 :            :  */
     329                 :            : 
     330                 :            : /**
     331                 :            :  * list_first_or_null_rcu - get the first element from a list
     332                 :            :  * @ptr:        the list head to take the element from.
     333                 :            :  * @type:       the type of the struct this is embedded in.
     334                 :            :  * @member:     the name of the list_head within the struct.
     335                 :            :  *
     336                 :            :  * Note that if the list is empty, it returns NULL.
     337                 :            :  *
     338                 :            :  * This primitive may safely run concurrently with the _rcu list-mutation
     339                 :            :  * primitives such as list_add_rcu() as long as it's guarded by rcu_read_lock().
     340                 :            :  */
     341                 :            : #define list_first_or_null_rcu(ptr, type, member) \
     342                 :            : ({ \
     343                 :            :         struct list_head *__ptr = (ptr); \
     344                 :            :         struct list_head *__next = READ_ONCE(__ptr->next); \
     345                 :            :         likely(__ptr != __next) ? list_entry_rcu(__next, type, member) : NULL; \
     346                 :            : })
     347                 :            : 
     348                 :            : /**
     349                 :            :  * list_next_or_null_rcu - get the first element from a list
     350                 :            :  * @head:       the head for the list.
     351                 :            :  * @ptr:        the list head to take the next element from.
     352                 :            :  * @type:       the type of the struct this is embedded in.
     353                 :            :  * @member:     the name of the list_head within the struct.
     354                 :            :  *
     355                 :            :  * Note that if the ptr is at the end of the list, NULL is returned.
     356                 :            :  *
     357                 :            :  * This primitive may safely run concurrently with the _rcu list-mutation
     358                 :            :  * primitives such as list_add_rcu() as long as it's guarded by rcu_read_lock().
     359                 :            :  */
     360                 :            : #define list_next_or_null_rcu(head, ptr, type, member) \
     361                 :            : ({ \
     362                 :            :         struct list_head *__head = (head); \
     363                 :            :         struct list_head *__ptr = (ptr); \
     364                 :            :         struct list_head *__next = READ_ONCE(__ptr->next); \
     365                 :            :         likely(__next != __head) ? list_entry_rcu(__next, type, \
     366                 :            :                                                   member) : NULL; \
     367                 :            : })
     368                 :            : 
     369                 :            : /**
     370                 :            :  * list_for_each_entry_rcu      -       iterate over rcu list of given type
     371                 :            :  * @pos:        the type * to use as a loop cursor.
     372                 :            :  * @head:       the head for your list.
     373                 :            :  * @member:     the name of the list_head within the struct.
     374                 :            :  * @cond...:    optional lockdep expression if called from non-RCU protection.
     375                 :            :  *
     376                 :            :  * This list-traversal primitive may safely run concurrently with
     377                 :            :  * the _rcu list-mutation primitives such as list_add_rcu()
     378                 :            :  * as long as the traversal is guarded by rcu_read_lock().
     379                 :            :  */
     380                 :            : #define list_for_each_entry_rcu(pos, head, member, cond...)             \
     381                 :            :         for (__list_check_rcu(dummy, ## cond, 0),                       \
     382                 :            :              pos = list_entry_rcu((head)->next, typeof(*pos), member);       \
     383                 :            :                 &pos->member != (head);                                  \
     384                 :            :                 pos = list_entry_rcu(pos->member.next, typeof(*pos), member))
     385                 :            : 
     386                 :            : /**
     387                 :            :  * list_entry_lockless - get the struct for this entry
     388                 :            :  * @ptr:        the &struct list_head pointer.
     389                 :            :  * @type:       the type of the struct this is embedded in.
     390                 :            :  * @member:     the name of the list_head within the struct.
     391                 :            :  *
     392                 :            :  * This primitive may safely run concurrently with the _rcu
     393                 :            :  * list-mutation primitives such as list_add_rcu(), but requires some
     394                 :            :  * implicit RCU read-side guarding.  One example is running within a special
     395                 :            :  * exception-time environment where preemption is disabled and where lockdep
     396                 :            :  * cannot be invoked.  Another example is when items are added to the list,
     397                 :            :  * but never deleted.
     398                 :            :  */
     399                 :            : #define list_entry_lockless(ptr, type, member) \
     400                 :            :         container_of((typeof(ptr))READ_ONCE(ptr), type, member)
     401                 :            : 
     402                 :            : /**
     403                 :            :  * list_for_each_entry_lockless - iterate over rcu list of given type
     404                 :            :  * @pos:        the type * to use as a loop cursor.
     405                 :            :  * @head:       the head for your list.
     406                 :            :  * @member:     the name of the list_struct within the struct.
     407                 :            :  *
     408                 :            :  * This primitive may safely run concurrently with the _rcu
     409                 :            :  * list-mutation primitives such as list_add_rcu(), but requires some
     410                 :            :  * implicit RCU read-side guarding.  One example is running within a special
     411                 :            :  * exception-time environment where preemption is disabled and where lockdep
     412                 :            :  * cannot be invoked.  Another example is when items are added to the list,
     413                 :            :  * but never deleted.
     414                 :            :  */
     415                 :            : #define list_for_each_entry_lockless(pos, head, member) \
     416                 :            :         for (pos = list_entry_lockless((head)->next, typeof(*pos), member); \
     417                 :            :              &pos->member != (head); \
     418                 :            :              pos = list_entry_lockless(pos->member.next, typeof(*pos), member))
     419                 :            : 
     420                 :            : /**
     421                 :            :  * list_for_each_entry_continue_rcu - continue iteration over list of given type
     422                 :            :  * @pos:        the type * to use as a loop cursor.
     423                 :            :  * @head:       the head for your list.
     424                 :            :  * @member:     the name of the list_head within the struct.
     425                 :            :  *
     426                 :            :  * Continue to iterate over list of given type, continuing after
     427                 :            :  * the current position which must have been in the list when the RCU read
     428                 :            :  * lock was taken.
     429                 :            :  * This would typically require either that you obtained the node from a
     430                 :            :  * previous walk of the list in the same RCU read-side critical section, or
     431                 :            :  * that you held some sort of non-RCU reference (such as a reference count)
     432                 :            :  * to keep the node alive *and* in the list.
     433                 :            :  *
     434                 :            :  * This iterator is similar to list_for_each_entry_from_rcu() except
     435                 :            :  * this starts after the given position and that one starts at the given
     436                 :            :  * position.
     437                 :            :  */
     438                 :            : #define list_for_each_entry_continue_rcu(pos, head, member)             \
     439                 :            :         for (pos = list_entry_rcu(pos->member.next, typeof(*pos), member); \
     440                 :            :              &pos->member != (head);     \
     441                 :            :              pos = list_entry_rcu(pos->member.next, typeof(*pos), member))
     442                 :            : 
     443                 :            : /**
     444                 :            :  * list_for_each_entry_from_rcu - iterate over a list from current point
     445                 :            :  * @pos:        the type * to use as a loop cursor.
     446                 :            :  * @head:       the head for your list.
     447                 :            :  * @member:     the name of the list_node within the struct.
     448                 :            :  *
     449                 :            :  * Iterate over the tail of a list starting from a given position,
     450                 :            :  * which must have been in the list when the RCU read lock was taken.
     451                 :            :  * This would typically require either that you obtained the node from a
     452                 :            :  * previous walk of the list in the same RCU read-side critical section, or
     453                 :            :  * that you held some sort of non-RCU reference (such as a reference count)
     454                 :            :  * to keep the node alive *and* in the list.
     455                 :            :  *
     456                 :            :  * This iterator is similar to list_for_each_entry_continue_rcu() except
     457                 :            :  * this starts from the given position and that one starts from the position
     458                 :            :  * after the given position.
     459                 :            :  */
     460                 :            : #define list_for_each_entry_from_rcu(pos, head, member)                 \
     461                 :            :         for (; &(pos)->member != (head);                                 \
     462                 :            :                 pos = list_entry_rcu(pos->member.next, typeof(*(pos)), member))
     463                 :            : 
     464                 :            : /**
     465                 :            :  * hlist_del_rcu - deletes entry from hash list without re-initialization
     466                 :            :  * @n: the element to delete from the hash list.
     467                 :            :  *
     468                 :            :  * Note: list_unhashed() on entry does not return true after this,
     469                 :            :  * the entry is in an undefined state. It is useful for RCU based
     470                 :            :  * lockfree traversal.
     471                 :            :  *
     472                 :            :  * In particular, it means that we can not poison the forward
     473                 :            :  * pointers that may still be used for walking the hash list.
     474                 :            :  *
     475                 :            :  * The caller must take whatever precautions are necessary
     476                 :            :  * (such as holding appropriate locks) to avoid racing
     477                 :            :  * with another list-mutation primitive, such as hlist_add_head_rcu()
     478                 :            :  * or hlist_del_rcu(), running on this same list.
     479                 :            :  * However, it is perfectly legal to run concurrently with
     480                 :            :  * the _rcu list-traversal primitives, such as
     481                 :            :  * hlist_for_each_entry().
     482                 :            :  */
     483                 :      52932 : static inline void hlist_del_rcu(struct hlist_node *n)
     484                 :            : {
     485   [ +  +  #  #  :      52932 :         __hlist_del(n);
          #  #  #  #  #  
             #  #  #  #  
                      # ]
     486   [ #  #  #  #  :      52932 :         WRITE_ONCE(n->pprev, LIST_POISON2);
          #  #  #  #  #  
                      # ]
     487                 :          0 : }
     488                 :            : 
     489                 :            : /**
     490                 :            :  * hlist_replace_rcu - replace old entry by new one
     491                 :            :  * @old : the element to be replaced
     492                 :            :  * @new : the new element to insert
     493                 :            :  *
     494                 :            :  * The @old entry will be replaced with the @new entry atomically.
     495                 :            :  */
     496                 :          0 : static inline void hlist_replace_rcu(struct hlist_node *old,
     497                 :            :                                         struct hlist_node *new)
     498                 :            : {
     499                 :          0 :         struct hlist_node *next = old->next;
     500                 :            : 
     501                 :          0 :         new->next = next;
     502                 :          0 :         WRITE_ONCE(new->pprev, old->pprev);
     503   [ #  #  #  # ]:          0 :         rcu_assign_pointer(*(struct hlist_node __rcu **)new->pprev, new);
     504   [ #  #  #  # ]:          0 :         if (next)
     505                 :          0 :                 WRITE_ONCE(new->next->pprev, &new->next);
     506                 :          0 :         WRITE_ONCE(old->pprev, LIST_POISON2);
     507                 :            : }
     508                 :            : 
     509                 :            : /*
     510                 :            :  * return the first or the next element in an RCU protected hlist
     511                 :            :  */
     512                 :            : #define hlist_first_rcu(head)   (*((struct hlist_node __rcu **)(&(head)->first)))
     513                 :            : #define hlist_next_rcu(node)    (*((struct hlist_node __rcu **)(&(node)->next)))
     514                 :            : #define hlist_pprev_rcu(node)   (*((struct hlist_node __rcu **)((node)->pprev)))
     515                 :            : 
     516                 :            : /**
     517                 :            :  * hlist_add_head_rcu
     518                 :            :  * @n: the element to add to the hash list.
     519                 :            :  * @h: the list to add to.
     520                 :            :  *
     521                 :            :  * Description:
     522                 :            :  * Adds the specified element to the specified hlist,
     523                 :            :  * while permitting racing traversals.
     524                 :            :  *
     525                 :            :  * The caller must take whatever precautions are necessary
     526                 :            :  * (such as holding appropriate locks) to avoid racing
     527                 :            :  * with another list-mutation primitive, such as hlist_add_head_rcu()
     528                 :            :  * or hlist_del_rcu(), running on this same list.
     529                 :            :  * However, it is perfectly legal to run concurrently with
     530                 :            :  * the _rcu list-traversal primitives, such as
     531                 :            :  * hlist_for_each_entry_rcu(), used to prevent memory-consistency
     532                 :            :  * problems on Alpha CPUs.  Regardless of the type of CPU, the
     533                 :            :  * list-traversal primitive must be guarded by rcu_read_lock().
     534                 :            :  */
     535                 :      80322 : static inline void hlist_add_head_rcu(struct hlist_node *n,
     536                 :            :                                         struct hlist_head *h)
     537                 :            : {
     538                 :      80322 :         struct hlist_node *first = h->first;
     539                 :            : 
     540                 :      80322 :         n->next = first;
     541                 :      80322 :         WRITE_ONCE(n->pprev, &h->first);
     542   [ +  +  +  +  :      80322 :         rcu_assign_pointer(hlist_first_rcu(h), n);
          -  +  -  -  -  
          +  #  #  #  #  
             #  #  #  # ]
     543   [ +  +  +  +  :      80322 :         if (first)
          -  +  -  -  -  
          +  #  #  #  #  
             #  #  #  # ]
     544                 :      30605 :                 WRITE_ONCE(first->pprev, &n->next);
     545                 :            : }
     546                 :            : 
     547                 :            : /**
     548                 :            :  * hlist_add_tail_rcu
     549                 :            :  * @n: the element to add to the hash list.
     550                 :            :  * @h: the list to add to.
     551                 :            :  *
     552                 :            :  * Description:
     553                 :            :  * Adds the specified element to the specified hlist,
     554                 :            :  * while permitting racing traversals.
     555                 :            :  *
     556                 :            :  * The caller must take whatever precautions are necessary
     557                 :            :  * (such as holding appropriate locks) to avoid racing
     558                 :            :  * with another list-mutation primitive, such as hlist_add_head_rcu()
     559                 :            :  * or hlist_del_rcu(), running on this same list.
     560                 :            :  * However, it is perfectly legal to run concurrently with
     561                 :            :  * the _rcu list-traversal primitives, such as
     562                 :            :  * hlist_for_each_entry_rcu(), used to prevent memory-consistency
     563                 :            :  * problems on Alpha CPUs.  Regardless of the type of CPU, the
     564                 :            :  * list-traversal primitive must be guarded by rcu_read_lock().
     565                 :            :  */
     566                 :       5940 : static inline void hlist_add_tail_rcu(struct hlist_node *n,
     567                 :            :                                       struct hlist_head *h)
     568                 :            : {
     569                 :       5940 :         struct hlist_node *i, *last = NULL;
     570                 :            : 
     571                 :            :         /* Note: write side code, so rcu accessors are not needed. */
     572   [ +  +  #  # ]:       6330 :         for (i = h->first; i; i = i->next)
     573                 :        390 :                 last = i;
     574                 :            : 
     575   [ +  +  #  # ]:       5940 :         if (last) {
     576                 :        390 :                 n->next = last->next;
     577                 :        390 :                 WRITE_ONCE(n->pprev, &last->next);
     578                 :        390 :                 rcu_assign_pointer(hlist_next_rcu(last), n);
     579                 :            :         } else {
     580                 :       5550 :                 hlist_add_head_rcu(n, h);
     581                 :            :         }
     582                 :            : }
     583                 :            : 
     584                 :            : /**
     585                 :            :  * hlist_add_before_rcu
     586                 :            :  * @n: the new element to add to the hash list.
     587                 :            :  * @next: the existing element to add the new element before.
     588                 :            :  *
     589                 :            :  * Description:
     590                 :            :  * Adds the specified element to the specified hlist
     591                 :            :  * before the specified node while permitting racing traversals.
     592                 :            :  *
     593                 :            :  * The caller must take whatever precautions are necessary
     594                 :            :  * (such as holding appropriate locks) to avoid racing
     595                 :            :  * with another list-mutation primitive, such as hlist_add_head_rcu()
     596                 :            :  * or hlist_del_rcu(), running on this same list.
     597                 :            :  * However, it is perfectly legal to run concurrently with
     598                 :            :  * the _rcu list-traversal primitives, such as
     599                 :            :  * hlist_for_each_entry_rcu(), used to prevent memory-consistency
     600                 :            :  * problems on Alpha CPUs.
     601                 :            :  */
     602                 :        486 : static inline void hlist_add_before_rcu(struct hlist_node *n,
     603                 :            :                                         struct hlist_node *next)
     604                 :            : {
     605                 :        486 :         WRITE_ONCE(n->pprev, next->pprev);
     606                 :        486 :         n->next = next;
     607                 :        486 :         rcu_assign_pointer(hlist_pprev_rcu(n), n);
     608                 :        486 :         WRITE_ONCE(next->pprev, &n->next);
     609                 :          0 : }
     610                 :            : 
     611                 :            : /**
     612                 :            :  * hlist_add_behind_rcu
     613                 :            :  * @n: the new element to add to the hash list.
     614                 :            :  * @prev: the existing element to add the new element after.
     615                 :            :  *
     616                 :            :  * Description:
     617                 :            :  * Adds the specified element to the specified hlist
     618                 :            :  * after the specified node while permitting racing traversals.
     619                 :            :  *
     620                 :            :  * The caller must take whatever precautions are necessary
     621                 :            :  * (such as holding appropriate locks) to avoid racing
     622                 :            :  * with another list-mutation primitive, such as hlist_add_head_rcu()
     623                 :            :  * or hlist_del_rcu(), running on this same list.
     624                 :            :  * However, it is perfectly legal to run concurrently with
     625                 :            :  * the _rcu list-traversal primitives, such as
     626                 :            :  * hlist_for_each_entry_rcu(), used to prevent memory-consistency
     627                 :            :  * problems on Alpha CPUs.
     628                 :            :  */
     629                 :         54 : static inline void hlist_add_behind_rcu(struct hlist_node *n,
     630                 :            :                                         struct hlist_node *prev)
     631                 :            : {
     632                 :         54 :         n->next = prev->next;
     633                 :         54 :         WRITE_ONCE(n->pprev, &prev->next);
     634   [ -  +  #  #  :         54 :         rcu_assign_pointer(hlist_next_rcu(prev), n);
          #  #  #  #  #  
                      # ]
     635   [ -  +  #  #  :         54 :         if (n->next)
          #  #  #  #  #  
                      # ]
     636                 :          0 :                 WRITE_ONCE(n->next->pprev, &n->next);
     637                 :            : }
     638                 :            : 
     639                 :            : #define __hlist_for_each_rcu(pos, head)                         \
     640                 :            :         for (pos = rcu_dereference(hlist_first_rcu(head));      \
     641                 :            :              pos;                                               \
     642                 :            :              pos = rcu_dereference(hlist_next_rcu(pos)))
     643                 :            : 
     644                 :            : /**
     645                 :            :  * hlist_for_each_entry_rcu - iterate over rcu list of given type
     646                 :            :  * @pos:        the type * to use as a loop cursor.
     647                 :            :  * @head:       the head for your list.
     648                 :            :  * @member:     the name of the hlist_node within the struct.
     649                 :            :  * @cond...:    optional lockdep expression if called from non-RCU protection.
     650                 :            :  *
     651                 :            :  * This list-traversal primitive may safely run concurrently with
     652                 :            :  * the _rcu list-mutation primitives such as hlist_add_head_rcu()
     653                 :            :  * as long as the traversal is guarded by rcu_read_lock().
     654                 :            :  */
     655                 :            : #define hlist_for_each_entry_rcu(pos, head, member, cond...)            \
     656                 :            :         for (__list_check_rcu(dummy, ## cond, 0),                       \
     657                 :            :              pos = hlist_entry_safe(rcu_dereference_raw(hlist_first_rcu(head)),\
     658                 :            :                         typeof(*(pos)), member);                        \
     659                 :            :                 pos;                                                    \
     660                 :            :                 pos = hlist_entry_safe(rcu_dereference_raw(hlist_next_rcu(\
     661                 :            :                         &(pos)->member)), typeof(*(pos)), member))
     662                 :            : 
     663                 :            : /**
     664                 :            :  * hlist_for_each_entry_rcu_notrace - iterate over rcu list of given type (for tracing)
     665                 :            :  * @pos:        the type * to use as a loop cursor.
     666                 :            :  * @head:       the head for your list.
     667                 :            :  * @member:     the name of the hlist_node within the struct.
     668                 :            :  *
     669                 :            :  * This list-traversal primitive may safely run concurrently with
     670                 :            :  * the _rcu list-mutation primitives such as hlist_add_head_rcu()
     671                 :            :  * as long as the traversal is guarded by rcu_read_lock().
     672                 :            :  *
     673                 :            :  * This is the same as hlist_for_each_entry_rcu() except that it does
     674                 :            :  * not do any RCU debugging or tracing.
     675                 :            :  */
     676                 :            : #define hlist_for_each_entry_rcu_notrace(pos, head, member)                     \
     677                 :            :         for (pos = hlist_entry_safe(rcu_dereference_raw_check(hlist_first_rcu(head)),\
     678                 :            :                         typeof(*(pos)), member);                        \
     679                 :            :                 pos;                                                    \
     680                 :            :                 pos = hlist_entry_safe(rcu_dereference_raw_check(hlist_next_rcu(\
     681                 :            :                         &(pos)->member)), typeof(*(pos)), member))
     682                 :            : 
     683                 :            : /**
     684                 :            :  * hlist_for_each_entry_rcu_bh - iterate over rcu list of given type
     685                 :            :  * @pos:        the type * to use as a loop cursor.
     686                 :            :  * @head:       the head for your list.
     687                 :            :  * @member:     the name of the hlist_node within the struct.
     688                 :            :  *
     689                 :            :  * This list-traversal primitive may safely run concurrently with
     690                 :            :  * the _rcu list-mutation primitives such as hlist_add_head_rcu()
     691                 :            :  * as long as the traversal is guarded by rcu_read_lock().
     692                 :            :  */
     693                 :            : #define hlist_for_each_entry_rcu_bh(pos, head, member)                  \
     694                 :            :         for (pos = hlist_entry_safe(rcu_dereference_bh(hlist_first_rcu(head)),\
     695                 :            :                         typeof(*(pos)), member);                        \
     696                 :            :                 pos;                                                    \
     697                 :            :                 pos = hlist_entry_safe(rcu_dereference_bh(hlist_next_rcu(\
     698                 :            :                         &(pos)->member)), typeof(*(pos)), member))
     699                 :            : 
     700                 :            : /**
     701                 :            :  * hlist_for_each_entry_continue_rcu - iterate over a hlist continuing after current point
     702                 :            :  * @pos:        the type * to use as a loop cursor.
     703                 :            :  * @member:     the name of the hlist_node within the struct.
     704                 :            :  */
     705                 :            : #define hlist_for_each_entry_continue_rcu(pos, member)                  \
     706                 :            :         for (pos = hlist_entry_safe(rcu_dereference_raw(hlist_next_rcu( \
     707                 :            :                         &(pos)->member)), typeof(*(pos)), member);       \
     708                 :            :              pos;                                                       \
     709                 :            :              pos = hlist_entry_safe(rcu_dereference_raw(hlist_next_rcu( \
     710                 :            :                         &(pos)->member)), typeof(*(pos)), member))
     711                 :            : 
     712                 :            : /**
     713                 :            :  * hlist_for_each_entry_continue_rcu_bh - iterate over a hlist continuing after current point
     714                 :            :  * @pos:        the type * to use as a loop cursor.
     715                 :            :  * @member:     the name of the hlist_node within the struct.
     716                 :            :  */
     717                 :            : #define hlist_for_each_entry_continue_rcu_bh(pos, member)               \
     718                 :            :         for (pos = hlist_entry_safe(rcu_dereference_bh(hlist_next_rcu(  \
     719                 :            :                         &(pos)->member)), typeof(*(pos)), member);       \
     720                 :            :              pos;                                                       \
     721                 :            :              pos = hlist_entry_safe(rcu_dereference_bh(hlist_next_rcu(  \
     722                 :            :                         &(pos)->member)), typeof(*(pos)), member))
     723                 :            : 
     724                 :            : /**
     725                 :            :  * hlist_for_each_entry_from_rcu - iterate over a hlist continuing from current point
     726                 :            :  * @pos:        the type * to use as a loop cursor.
     727                 :            :  * @member:     the name of the hlist_node within the struct.
     728                 :            :  */
     729                 :            : #define hlist_for_each_entry_from_rcu(pos, member)                      \
     730                 :            :         for (; pos;                                                     \
     731                 :            :              pos = hlist_entry_safe(rcu_dereference_raw(hlist_next_rcu( \
     732                 :            :                         &(pos)->member)), typeof(*(pos)), member))
     733                 :            : 
     734                 :            : #endif  /* __KERNEL__ */
     735                 :            : #endif

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