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 /* SPDX-License-Identifier: GPL-2.0 */
 #ifndef _LINUX_RCULIST_H
 #define _LINUX_RCULIST_H
 
 #ifdef __KERNEL__
 
 /*
  * RCU-protected list version
  */
 #include <linux/list.h>
 #include <linux/rcupdate.h>
 
 /*
  * INIT_LIST_HEAD_RCU - Initialize a list_head visible to RCU readers
  * @list: list to be initialized
  *
  * You should instead use INIT_LIST_HEAD() for normal initialization and
  * cleanup tasks, when readers have no access to the list being initialized.
  * However, if the list being initialized is visible to readers, you
  * need to keep the compiler from being too mischievous.
  */
 static inline void INIT_LIST_HEAD_RCU(struct list_head *list)
 {
     WRITE_ONCE(list->next, list);
     WRITE_ONCE(list->prev, list);
 }
 
 /*
  * return the ->next pointer of a list_head in an rcu safe
  * way, we must not access it directly
  */
 #define list_next_rcu(list) (*((struct list_head __rcu **)(&(list)->next)))
 
 /**
  * list_tail_rcu - returns the prev pointer of the head of the list
  * @head: the head of the list
  *
  * Note: This should only be used with the list header, and even then
  * only if list_del() and similar primitives are not also used on the
  * list header.
  */
 #define list_tail_rcu(head) (*((struct list_head __rcu **)(&(head)->prev)))
 
 /*
  * Check during list traversal that we are within an RCU reader
  */
 
 #define check_arg_count_one(dummy)
 
 #ifdef CONFIG_PROVE_RCU_LIST
 #define __list_check_rcu(dummy, cond, extra...)             \
     ({                              \
     check_arg_count_one(extra);                 \
     RCU_LOCKDEP_WARN(!(cond) && !rcu_read_lock_any_held(),      \
              "RCU-list traversed in non-reader section!");  \
     })
 
 #define __list_check_srcu(cond)                  \
     ({                               \
     RCU_LOCKDEP_WARN(!(cond),                    \
         "RCU-list traversed without holding the required lock!");\
     })
 #else
 #define __list_check_rcu(dummy, cond, extra...)             \
     ({ check_arg_count_one(extra); })
 
 #define __list_check_srcu(cond) ({ })
 #endif
 
 /*
  * Insert a new entry between two known consecutive entries.
  *
  * This is only for internal list manipulation where we know
  * the prev/next entries already!
  */
 static inline void __list_add_rcu(struct list_head *new,
         struct list_head *prev, struct list_head *next)
 {
     if (!__list_add_valid(new, prev, next))
         return;
 
     new->next = next;
     new->prev = prev;
     rcu_assign_pointer(list_next_rcu(prev), new);
     next->prev = new;
 }
 
 /**
  * list_add_rcu - add a new entry to rcu-protected list
  * @new: new entry to be added
  * @head: list head to add it after
  *
  * Insert a new entry after the specified head.
  * This is good for implementing stacks.
  *
  * The caller must take whatever precautions are necessary
  * (such as holding appropriate locks) to avoid racing
  * with another list-mutation primitive, such as list_add_rcu()
  * or list_del_rcu(), running on this same list.
  * However, it is perfectly legal to run concurrently with
  * the _rcu list-traversal primitives, such as
  * list_for_each_entry_rcu().
  */
 static inline void list_add_rcu(struct list_head *new, struct list_head *head)
 {
     __list_add_rcu(new, head, head->next);
 }
 
 /**
  * list_add_tail_rcu - add a new entry to rcu-protected list
  * @new: new entry to be added
  * @head: list head to add it before
  *
  * Insert a new entry before the specified head.
  * This is useful for implementing queues.
  *
  * The caller must take whatever precautions are necessary
  * (such as holding appropriate locks) to avoid racing
  * with another list-mutation primitive, such as list_add_tail_rcu()
  * or list_del_rcu(), running on this same list.
  * However, it is perfectly legal to run concurrently with
  * the _rcu list-traversal primitives, such as
  * list_for_each_entry_rcu().
  */
 static inline void list_add_tail_rcu(struct list_head *new,
                     struct list_head *head)
 {
     __list_add_rcu(new, head->prev, head);
 }
 
 /**
  * list_del_rcu - deletes entry from list without re-initialization
  * @entry: the element to delete from the list.
  *
  * Note: list_empty() on entry does not return true after this,
  * the entry is in an undefined state. It is useful for RCU based
  * lockfree traversal.
  *
  * In particular, it means that we can not poison the forward
  * pointers that may still be used for walking the list.
  *
  * The caller must take whatever precautions are necessary
  * (such as holding appropriate locks) to avoid racing
  * with another list-mutation primitive, such as list_del_rcu()
  * or list_add_rcu(), running on this same list.
  * However, it is perfectly legal to run concurrently with
  * the _rcu list-traversal primitives, such as
  * list_for_each_entry_rcu().
  *
  * Note that the caller is not permitted to immediately free
  * the newly deleted entry.  Instead, either synchronize_rcu()
  * or call_rcu() must be used to defer freeing until an RCU
  * grace period has elapsed.
  */
 static inline void list_del_rcu(struct list_head *entry)
 {
     __list_del_entry(entry);
     entry->prev = LIST_POISON2;
 }
 
 /**
  * hlist_del_init_rcu - deletes entry from hash list with re-initialization
  * @n: the element to delete from the hash list.
  *
  * Note: list_unhashed() on the node return true after this. It is
  * useful for RCU based read lockfree traversal if the writer side
  * must know if the list entry is still hashed or already unhashed.
  *
  * In particular, it means that we can not poison the forward pointers
  * that may still be used for walking the hash list and we can only
  * zero the pprev pointer so list_unhashed() will return true after
  * this.
  *
  * The caller must take whatever precautions are necessary (such as
  * holding appropriate locks) to avoid racing with another
  * list-mutation primitive, such as hlist_add_head_rcu() or
  * hlist_del_rcu(), running on this same list.  However, it is
  * perfectly legal to run concurrently with the _rcu list-traversal
  * primitives, such as hlist_for_each_entry_rcu().
  */
 static inline void hlist_del_init_rcu(struct hlist_node *n)
 {
     if (!hlist_unhashed(n)) {
         __hlist_del(n);
         WRITE_ONCE(n->pprev, NULL);
     }
 }
 
 /**
  * list_replace_rcu - replace old entry by new one
  * @old : the element to be replaced
  * @new : the new element to insert
  *
  * The @old entry will be replaced with the @new entry atomically.
  * Note: @old should not be empty.
  */
 static inline void list_replace_rcu(struct list_head *old,
                 struct list_head *new)
 {
     new->next = old->next;
     new->prev = old->prev;
     rcu_assign_pointer(list_next_rcu(new->prev), new);
     new->next->prev = new;
     old->prev = LIST_POISON2;
 }
 
 /**
  * __list_splice_init_rcu - join an RCU-protected list into an existing list.
  * @list:   the RCU-protected list to splice
  * @prev:   points to the last element of the existing list
  * @next:   points to the first element of the existing list
  * @sync:   synchronize_rcu, synchronize_rcu_expedited, ...
  *
  * The list pointed to by @prev and @next can be RCU-read traversed
  * concurrently with this function.
  *
  * Note that this function blocks.
  *
  * Important note: the caller must take whatever action is necessary to prevent
  * any other updates to the existing list.  In principle, it is possible to
  * modify the list as soon as sync() begins execution. If this sort of thing
  * becomes necessary, an alternative version based on call_rcu() could be
  * created.  But only if -really- needed -- there is no shortage of RCU API
  * members.
  */
 static inline void __list_splice_init_rcu(struct list_head *list,
                       struct list_head *prev,
                       struct list_head *next,
                       void (*sync)(void))
 {
     struct list_head *first = list->next;
     struct list_head *last = list->prev;
 
     /*
      * "first" and "last" tracking list, so initialize it.  RCU readers
      * have access to this list, so we must use INIT_LIST_HEAD_RCU()
      * instead of INIT_LIST_HEAD().
      */
 
     INIT_LIST_HEAD_RCU(list);
 
     /*
      * At this point, the list body still points to the source list.
      * Wait for any readers to finish using the list before splicing
      * the list body into the new list.  Any new readers will see
      * an empty list.
      */
 
     sync();
     ASSERT_EXCLUSIVE_ACCESS(*first);
     ASSERT_EXCLUSIVE_ACCESS(*last);
 
     /*
      * Readers are finished with the source list, so perform splice.
      * The order is important if the new list is global and accessible
      * to concurrent RCU readers.  Note that RCU readers are not
      * permitted to traverse the prev pointers without excluding
      * this function.
      */
 
     last->next = next;
     rcu_assign_pointer(list_next_rcu(prev), first);
     first->prev = prev;
     next->prev = last;
 }
 
 /**
  * list_splice_init_rcu - splice an RCU-protected list into an existing list,
  *                        designed for stacks.
  * @list:   the RCU-protected list to splice
  * @head:   the place in the existing list to splice the first list into
  * @sync:   synchronize_rcu, synchronize_rcu_expedited, ...
  */
 static inline void list_splice_init_rcu(struct list_head *list,
                     struct list_head *head,
                     void (*sync)(void))
 {
     if (!list_empty(list))
         __list_splice_init_rcu(list, head, head->next, sync);
 }
 
 /**
  * list_splice_tail_init_rcu - splice an RCU-protected list into an existing
  *                             list, designed for queues.
  * @list:   the RCU-protected list to splice
  * @head:   the place in the existing list to splice the first list into
  * @sync:   synchronize_rcu, synchronize_rcu_expedited, ...
  */
 static inline void list_splice_tail_init_rcu(struct list_head *list,
                          struct list_head *head,
                          void (*sync)(void))
 {
     if (!list_empty(list))
         __list_splice_init_rcu(list, head->prev, head, sync);
 }
 
 /**
  * list_entry_rcu - get the struct for this entry
  * @ptr:        the &struct list_head pointer.
  * @type:       the type of the struct this is embedded in.
  * @member:     the name of the list_head within the struct.
  *
  * This primitive may safely run concurrently with the _rcu list-mutation
  * primitives such as list_add_rcu() as long as it's guarded by rcu_read_lock().
  */
 #define list_entry_rcu(ptr, type, member) \
     container_of(READ_ONCE(ptr), type, member)
 
 /*
  * Where are list_empty_rcu() and list_first_entry_rcu()?
  *
  * They do not exist because they would lead to subtle race conditions:
  *
  * if (!list_empty_rcu(mylist)) {
  *  struct foo *bar = list_first_entry_rcu(mylist, struct foo, list_member);
  *  do_something(bar);
  * }
  *
  * The list might be non-empty when list_empty_rcu() checks it, but it
  * might have become empty by the time that list_first_entry_rcu() rereads
  * the ->next pointer, which would result in a SEGV.
  *
  * When not using RCU, it is OK for list_first_entry() to re-read that
  * pointer because both functions should be protected by some lock that
  * blocks writers.
  *
  * When using RCU, list_empty() uses READ_ONCE() to fetch the
  * RCU-protected ->next pointer and then compares it to the address of the
  * list head.  However, it neither dereferences this pointer nor provides
  * this pointer to its caller.  Thus, READ_ONCE() suffices (that is,
  * rcu_dereference() is not needed), which means that list_empty() can be
  * used anywhere you would want to use list_empty_rcu().  Just don't
  * expect anything useful to happen if you do a subsequent lockless
  * call to list_first_entry_rcu()!!!
  *
  * See list_first_or_null_rcu for an alternative.
  */
 
 /**
  * list_first_or_null_rcu - get the first element from a list
  * @ptr:        the list head to take the element from.
  * @type:       the type of the struct this is embedded in.
  * @member:     the name of the list_head within the struct.
  *
  * Note that if the list is empty, it returns NULL.
  *
  * This primitive may safely run concurrently with the _rcu list-mutation
  * primitives such as list_add_rcu() as long as it's guarded by rcu_read_lock().
  */
 #define list_first_or_null_rcu(ptr, type, member) \
 ({ \
     struct list_head *__ptr = (ptr); \
     struct list_head *__next = READ_ONCE(__ptr->next); \
     likely(__ptr != __next) ? list_entry_rcu(__next, type, member) : NULL; \
 })
 
 /**
  * list_next_or_null_rcu - get the first element from a list
  * @head:   the head for the list.
  * @ptr:        the list head to take the next element from.
  * @type:       the type of the struct this is embedded in.
  * @member:     the name of the list_head within the struct.
  *
  * Note that if the ptr is at the end of the list, NULL is returned.
  *
  * This primitive may safely run concurrently with the _rcu list-mutation
  * primitives such as list_add_rcu() as long as it's guarded by rcu_read_lock().
  */
 #define list_next_or_null_rcu(head, ptr, type, member) \
 ({ \
     struct list_head *__head = (head); \
     struct list_head *__ptr = (ptr); \
     struct list_head *__next = READ_ONCE(__ptr->next); \
     likely(__next != __head) ? list_entry_rcu(__next, type, \
                           member) : NULL; \
 })
 
 /**
  * list_for_each_entry_rcu  -   iterate over rcu list of given type
  * @pos:    the type * to use as a loop cursor.
  * @head:   the head for your list.
  * @member: the name of the list_head within the struct.
  * @cond:   optional lockdep expression if called from non-RCU protection.
  *
  * This list-traversal primitive may safely run concurrently with
  * the _rcu list-mutation primitives such as list_add_rcu()
  * as long as the traversal is guarded by rcu_read_lock().
  */
 #define list_for_each_entry_rcu(pos, head, member, cond...)     \
     for (__list_check_rcu(dummy, ## cond, 0),           \
          pos = list_entry_rcu((head)->next, typeof(*pos), member);  \
         &pos->member != (head);                 \
         pos = list_entry_rcu(pos->member.next, typeof(*pos), member))
 
 /**
  * list_for_each_entry_srcu -   iterate over rcu list of given type
  * @pos:    the type * to use as a loop cursor.
  * @head:   the head for your list.
  * @member: the name of the list_head within the struct.
  * @cond:   lockdep expression for the lock required to traverse the list.
  *
  * This list-traversal primitive may safely run concurrently with
  * the _rcu list-mutation primitives such as list_add_rcu()
  * as long as the traversal is guarded by srcu_read_lock().
  * The lockdep expression srcu_read_lock_held() can be passed as the
  * cond argument from read side.
  */
 #define list_for_each_entry_srcu(pos, head, member, cond)       \
     for (__list_check_srcu(cond),                   \
          pos = list_entry_rcu((head)->next, typeof(*pos), member);  \
         &pos->member != (head);                 \
         pos = list_entry_rcu(pos->member.next, typeof(*pos), member))
 
 /**
  * list_entry_lockless - get the struct for this entry
  * @ptr:        the &struct list_head pointer.
  * @type:       the type of the struct this is embedded in.
  * @member:     the name of the list_head within the struct.
  *
  * This primitive may safely run concurrently with the _rcu
  * list-mutation primitives such as list_add_rcu(), but requires some
  * implicit RCU read-side guarding.  One example is running within a special
  * exception-time environment where preemption is disabled and where lockdep
  * cannot be invoked.  Another example is when items are added to the list,
  * but never deleted.
  */
 #define list_entry_lockless(ptr, type, member) \
     container_of((typeof(ptr))READ_ONCE(ptr), type, member)
 
 /**
  * list_for_each_entry_lockless - iterate over rcu list of given type
  * @pos:    the type * to use as a loop cursor.
  * @head:   the head for your list.
  * @member: the name of the list_struct within the struct.
  *
  * This primitive may safely run concurrently with the _rcu
  * list-mutation primitives such as list_add_rcu(), but requires some
  * implicit RCU read-side guarding.  One example is running within a special
  * exception-time environment where preemption is disabled and where lockdep
  * cannot be invoked.  Another example is when items are added to the list,
  * but never deleted.
  */
 #define list_for_each_entry_lockless(pos, head, member) \
     for (pos = list_entry_lockless((head)->next, typeof(*pos), member); \
          &pos->member != (head); \
          pos = list_entry_lockless(pos->member.next, typeof(*pos), member))
 
 /**
  * list_for_each_entry_continue_rcu - continue iteration over list of given type
  * @pos:    the type * to use as a loop cursor.
  * @head:   the head for your list.
  * @member: the name of the list_head within the struct.
  *
  * Continue to iterate over list of given type, continuing after
  * the current position which must have been in the list when the RCU read
  * lock was taken.
  * This would typically require either that you obtained the node from a
  * previous walk of the list in the same RCU read-side critical section, or
  * that you held some sort of non-RCU reference (such as a reference count)
  * to keep the node alive *and* in the list.
  *
  * This iterator is similar to list_for_each_entry_from_rcu() except
  * this starts after the given position and that one starts at the given
  * position.
  */
 #define list_for_each_entry_continue_rcu(pos, head, member)         \
     for (pos = list_entry_rcu(pos->member.next, typeof(*pos), member); \
          &pos->member != (head);    \
          pos = list_entry_rcu(pos->member.next, typeof(*pos), member))
 
 /**
  * list_for_each_entry_from_rcu - iterate over a list from current point
  * @pos:    the type * to use as a loop cursor.
  * @head:   the head for your list.
  * @member: the name of the list_node within the struct.
  *
  * Iterate over the tail of a list starting from a given position,
  * which must have been in the list when the RCU read lock was taken.
  * This would typically require either that you obtained the node from a
  * previous walk of the list in the same RCU read-side critical section, or
  * that you held some sort of non-RCU reference (such as a reference count)
  * to keep the node alive *and* in the list.
  *
  * This iterator is similar to list_for_each_entry_continue_rcu() except
  * this starts from the given position and that one starts from the position
  * after the given position.
  */
 #define list_for_each_entry_from_rcu(pos, head, member)         \
     for (; &(pos)->member != (head);                    \
         pos = list_entry_rcu(pos->member.next, typeof(*(pos)), member))
 
 /**
  * hlist_del_rcu - deletes entry from hash list without re-initialization
  * @n: the element to delete from the hash list.
  *
  * Note: list_unhashed() on entry does not return true after this,
  * the entry is in an undefined state. It is useful for RCU based
  * lockfree traversal.
  *
  * In particular, it means that we can not poison the forward
  * pointers that may still be used for walking the hash list.
  *
  * The caller must take whatever precautions are necessary
  * (such as holding appropriate locks) to avoid racing
  * with another list-mutation primitive, such as hlist_add_head_rcu()
  * or hlist_del_rcu(), running on this same list.
  * However, it is perfectly legal to run concurrently with
  * the _rcu list-traversal primitives, such as
  * hlist_for_each_entry().
  */
 static inline void hlist_del_rcu(struct hlist_node *n)
 {
     __hlist_del(n);
     WRITE_ONCE(n->pprev, LIST_POISON2);
 }
 
 /**
  * hlist_replace_rcu - replace old entry by new one
  * @old : the element to be replaced
  * @new : the new element to insert
  *
  * The @old entry will be replaced with the @new entry atomically.
  */
 static inline void hlist_replace_rcu(struct hlist_node *old,
                     struct hlist_node *new)
 {
     struct hlist_node *next = old->next;
 
     new->next = next;
     WRITE_ONCE(new->pprev, old->pprev);
     rcu_assign_pointer(*(struct hlist_node __rcu **)new->pprev, new);
     if (next)
         WRITE_ONCE(new->next->pprev, &new->next);
     WRITE_ONCE(old->pprev, LIST_POISON2);
 }
 
 /**
  * hlists_swap_heads_rcu - swap the lists the hlist heads point to
  * @left:  The hlist head on the left
  * @right: The hlist head on the right
  *
  * The lists start out as [@left  ][node1 ... ] and
  *                        [@right ][node2 ... ]
  * The lists end up as    [@left  ][node2 ... ]
  *                        [@right ][node1 ... ]
  */
 static inline void hlists_swap_heads_rcu(struct hlist_head *left, struct hlist_head *right)
 {
     struct hlist_node *node1 = left->first;
     struct hlist_node *node2 = right->first;
 
     rcu_assign_pointer(left->first, node2);
     rcu_assign_pointer(right->first, node1);
     WRITE_ONCE(node2->pprev, &left->first);
     WRITE_ONCE(node1->pprev, &right->first);
 }
 
 /*
  * return the first or the next element in an RCU protected hlist
  */
 #define hlist_first_rcu(head)   (*((struct hlist_node __rcu **)(&(head)->first)))
 #define hlist_next_rcu(node)    (*((struct hlist_node __rcu **)(&(node)->next)))
 #define hlist_pprev_rcu(node)   (*((struct hlist_node __rcu **)((node)->pprev)))
 
 /**
  * hlist_add_head_rcu
  * @n: the element to add to the hash list.
  * @h: the list to add to.
  *
  * Description:
  * Adds the specified element to the specified hlist,
  * while permitting racing traversals.
  *
  * The caller must take whatever precautions are necessary
  * (such as holding appropriate locks) to avoid racing
  * with another list-mutation primitive, such as hlist_add_head_rcu()
  * or hlist_del_rcu(), running on this same list.
  * However, it is perfectly legal to run concurrently with
  * the _rcu list-traversal primitives, such as
  * hlist_for_each_entry_rcu(), used to prevent memory-consistency
  * problems on Alpha CPUs.  Regardless of the type of CPU, the
  * list-traversal primitive must be guarded by rcu_read_lock().
  */
 static inline void hlist_add_head_rcu(struct hlist_node *n,
                     struct hlist_head *h)
 {
     struct hlist_node *first = h->first;
 
     n->next = first;
     WRITE_ONCE(n->pprev, &h->first);
     rcu_assign_pointer(hlist_first_rcu(h), n);
     if (first)
         WRITE_ONCE(first->pprev, &n->next);
 }
 
 /**
  * hlist_add_tail_rcu
  * @n: the element to add to the hash list.
  * @h: the list to add to.
  *
  * Description:
  * Adds the specified element to the specified hlist,
  * while permitting racing traversals.
  *
  * The caller must take whatever precautions are necessary
  * (such as holding appropriate locks) to avoid racing
  * with another list-mutation primitive, such as hlist_add_head_rcu()
  * or hlist_del_rcu(), running on this same list.
  * However, it is perfectly legal to run concurrently with
  * the _rcu list-traversal primitives, such as
  * hlist_for_each_entry_rcu(), used to prevent memory-consistency
  * problems on Alpha CPUs.  Regardless of the type of CPU, the
  * list-traversal primitive must be guarded by rcu_read_lock().
  */
 static inline void hlist_add_tail_rcu(struct hlist_node *n,
                       struct hlist_head *h)
 {
     struct hlist_node *i, *last = NULL;
 
     /* Note: write side code, so rcu accessors are not needed. */
     for (i = h->first; i; i = i->next)
         last = i;
 
     if (last) {
         n->next = last->next;
         WRITE_ONCE(n->pprev, &last->next);
         rcu_assign_pointer(hlist_next_rcu(last), n);
     } else {
         hlist_add_head_rcu(n, h);
     }
 }
 
 /**
  * hlist_add_before_rcu
  * @n: the new element to add to the hash list.
  * @next: the existing element to add the new element before.
  *
  * Description:
  * Adds the specified element to the specified hlist
  * before the specified node while permitting racing traversals.
  *
  * The caller must take whatever precautions are necessary
  * (such as holding appropriate locks) to avoid racing
  * with another list-mutation primitive, such as hlist_add_head_rcu()
  * or hlist_del_rcu(), running on this same list.
  * However, it is perfectly legal to run concurrently with
  * the _rcu list-traversal primitives, such as
  * hlist_for_each_entry_rcu(), used to prevent memory-consistency
  * problems on Alpha CPUs.
  */
 static inline void hlist_add_before_rcu(struct hlist_node *n,
                     struct hlist_node *next)
 {
     WRITE_ONCE(n->pprev, next->pprev);
     n->next = next;
     rcu_assign_pointer(hlist_pprev_rcu(n), n);
     WRITE_ONCE(next->pprev, &n->next);
 }
 
 /**
  * hlist_add_behind_rcu
  * @n: the new element to add to the hash list.
  * @prev: the existing element to add the new element after.
  *
  * Description:
  * Adds the specified element to the specified hlist
  * after the specified node while permitting racing traversals.
  *
  * The caller must take whatever precautions are necessary
  * (such as holding appropriate locks) to avoid racing
  * with another list-mutation primitive, such as hlist_add_head_rcu()
  * or hlist_del_rcu(), running on this same list.
  * However, it is perfectly legal to run concurrently with
  * the _rcu list-traversal primitives, such as
  * hlist_for_each_entry_rcu(), used to prevent memory-consistency
  * problems on Alpha CPUs.
  */
 static inline void hlist_add_behind_rcu(struct hlist_node *n,
                     struct hlist_node *prev)
 {
     n->next = prev->next;
     WRITE_ONCE(n->pprev, &prev->next);
     rcu_assign_pointer(hlist_next_rcu(prev), n);
     if (n->next)
         WRITE_ONCE(n->next->pprev, &n->next);
 }
 
 #define __hlist_for_each_rcu(pos, head)             \
     for (pos = rcu_dereference(hlist_first_rcu(head));  \
          pos;                       \
          pos = rcu_dereference(hlist_next_rcu(pos)))
 
 /**
  * hlist_for_each_entry_rcu - iterate over rcu list of given type
  * @pos:    the type * to use as a loop cursor.
  * @head:   the head for your list.
  * @member: the name of the hlist_node within the struct.
  * @cond:   optional lockdep expression if called from non-RCU protection.
  *
  * This list-traversal primitive may safely run concurrently with
  * the _rcu list-mutation primitives such as hlist_add_head_rcu()
  * as long as the traversal is guarded by rcu_read_lock().
  */
 #define hlist_for_each_entry_rcu(pos, head, member, cond...)        \
     for (__list_check_rcu(dummy, ## cond, 0),           \
          pos = hlist_entry_safe(rcu_dereference_raw(hlist_first_rcu(head)),\
             typeof(*(pos)), member);            \
         pos;                            \
         pos = hlist_entry_safe(rcu_dereference_raw(hlist_next_rcu(\
             &(pos)->member)), typeof(*(pos)), member))
 
 /**
  * hlist_for_each_entry_srcu - iterate over rcu list of given type
  * @pos:    the type * to use as a loop cursor.
  * @head:   the head for your list.
  * @member: the name of the hlist_node within the struct.
  * @cond:   lockdep expression for the lock required to traverse the list.
  *
  * This list-traversal primitive may safely run concurrently with
  * the _rcu list-mutation primitives such as hlist_add_head_rcu()
  * as long as the traversal is guarded by srcu_read_lock().
  * The lockdep expression srcu_read_lock_held() can be passed as the
  * cond argument from read side.
  */
 #define hlist_for_each_entry_srcu(pos, head, member, cond)      \
     for (__list_check_srcu(cond),                   \
          pos = hlist_entry_safe(rcu_dereference_raw(hlist_first_rcu(head)),\
             typeof(*(pos)), member);            \
         pos;                            \
         pos = hlist_entry_safe(rcu_dereference_raw(hlist_next_rcu(\
             &(pos)->member)), typeof(*(pos)), member))
 
 /**
  * hlist_for_each_entry_rcu_notrace - iterate over rcu list of given type (for tracing)
  * @pos:    the type * to use as a loop cursor.
  * @head:   the head for your list.
  * @member: the name of the hlist_node within the struct.
  *
  * This list-traversal primitive may safely run concurrently with
  * the _rcu list-mutation primitives such as hlist_add_head_rcu()
  * as long as the traversal is guarded by rcu_read_lock().
  *
  * This is the same as hlist_for_each_entry_rcu() except that it does
  * not do any RCU debugging or tracing.
  */
 #define hlist_for_each_entry_rcu_notrace(pos, head, member)         \
     for (pos = hlist_entry_safe(rcu_dereference_raw_check(hlist_first_rcu(head)),\
             typeof(*(pos)), member);            \
         pos;                            \
         pos = hlist_entry_safe(rcu_dereference_raw_check(hlist_next_rcu(\
             &(pos)->member)), typeof(*(pos)), member))
 
 /**
  * hlist_for_each_entry_rcu_bh - iterate over rcu list of given type
  * @pos:    the type * to use as a loop cursor.
  * @head:   the head for your list.
  * @member: the name of the hlist_node within the struct.
  *
  * This list-traversal primitive may safely run concurrently with
  * the _rcu list-mutation primitives such as hlist_add_head_rcu()
  * as long as the traversal is guarded by rcu_read_lock().
  */
 #define hlist_for_each_entry_rcu_bh(pos, head, member)          \
     for (pos = hlist_entry_safe(rcu_dereference_bh(hlist_first_rcu(head)),\
             typeof(*(pos)), member);            \
         pos;                            \
         pos = hlist_entry_safe(rcu_dereference_bh(hlist_next_rcu(\
             &(pos)->member)), typeof(*(pos)), member))
 
 /**
  * hlist_for_each_entry_continue_rcu - iterate over a hlist continuing after current point
  * @pos:    the type * to use as a loop cursor.
  * @member: the name of the hlist_node within the struct.
  */
 #define hlist_for_each_entry_continue_rcu(pos, member)          \
     for (pos = hlist_entry_safe(rcu_dereference_raw(hlist_next_rcu( \
             &(pos)->member)), typeof(*(pos)), member);  \
          pos;                           \
          pos = hlist_entry_safe(rcu_dereference_raw(hlist_next_rcu( \
             &(pos)->member)), typeof(*(pos)), member))
 
 /**
  * hlist_for_each_entry_continue_rcu_bh - iterate over a hlist continuing after current point
  * @pos:    the type * to use as a loop cursor.
  * @member: the name of the hlist_node within the struct.
  */
 #define hlist_for_each_entry_continue_rcu_bh(pos, member)       \
     for (pos = hlist_entry_safe(rcu_dereference_bh(hlist_next_rcu(  \
             &(pos)->member)), typeof(*(pos)), member);  \
          pos;                           \
          pos = hlist_entry_safe(rcu_dereference_bh(hlist_next_rcu(  \
             &(pos)->member)), typeof(*(pos)), member))
 
 /**
  * hlist_for_each_entry_from_rcu - iterate over a hlist continuing from current point
  * @pos:    the type * to use as a loop cursor.
  * @member: the name of the hlist_node within the struct.
  */
 #define hlist_for_each_entry_from_rcu(pos, member)          \
     for (; pos;                         \
          pos = hlist_entry_safe(rcu_dereference_raw(hlist_next_rcu( \
             &(pos)->member)), typeof(*(pos)), member))
 
 #endif  /* __KERNEL__ */
 #endif

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