388 lines
12 KiB
C
388 lines
12 KiB
C
#ifndef _LINUX_RCULIST_H
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#define _LINUX_RCULIST_H
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#ifdef __KERNEL__
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/*
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* RCU-protected list version
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*/
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#include <linux/list.h>
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#include <linux/rcupdate.h>
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/*
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* Insert a new entry between two known consecutive entries.
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*
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* This is only for internal list manipulation where we know
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* the prev/next entries already!
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*/
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static inline void __list_add_rcu(struct list_head *new,
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struct list_head *prev, struct list_head *next)
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{
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new->next = next;
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new->prev = prev;
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rcu_assign_pointer(prev->next, new);
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next->prev = new;
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}
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/**
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* list_add_rcu - add a new entry to rcu-protected list
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* @new: new entry to be added
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* @head: list head to add it after
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*
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* Insert a new entry after the specified head.
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* This is good for implementing stacks.
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*
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* The caller must take whatever precautions are necessary
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* (such as holding appropriate locks) to avoid racing
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* with another list-mutation primitive, such as list_add_rcu()
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* or list_del_rcu(), running on this same list.
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* However, it is perfectly legal to run concurrently with
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* the _rcu list-traversal primitives, such as
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* list_for_each_entry_rcu().
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*/
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static inline void list_add_rcu(struct list_head *new, struct list_head *head)
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{
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__list_add_rcu(new, head, head->next);
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}
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/**
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* list_add_tail_rcu - add a new entry to rcu-protected list
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* @new: new entry to be added
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* @head: list head to add it before
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*
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* Insert a new entry before the specified head.
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* This is useful for implementing queues.
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*
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* The caller must take whatever precautions are necessary
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* (such as holding appropriate locks) to avoid racing
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* with another list-mutation primitive, such as list_add_tail_rcu()
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* or list_del_rcu(), running on this same list.
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* However, it is perfectly legal to run concurrently with
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* the _rcu list-traversal primitives, such as
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* list_for_each_entry_rcu().
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*/
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static inline void list_add_tail_rcu(struct list_head *new,
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struct list_head *head)
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{
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__list_add_rcu(new, head->prev, head);
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}
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/**
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* list_del_rcu - deletes entry from list without re-initialization
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* @entry: the element to delete from the list.
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*
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* Note: list_empty() on entry does not return true after this,
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* the entry is in an undefined state. It is useful for RCU based
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* lockfree traversal.
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*
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* In particular, it means that we can not poison the forward
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* pointers that may still be used for walking the list.
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*
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* The caller must take whatever precautions are necessary
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* (such as holding appropriate locks) to avoid racing
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* with another list-mutation primitive, such as list_del_rcu()
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* or list_add_rcu(), running on this same list.
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* However, it is perfectly legal to run concurrently with
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* the _rcu list-traversal primitives, such as
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* list_for_each_entry_rcu().
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*
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* Note that the caller is not permitted to immediately free
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* the newly deleted entry. Instead, either synchronize_rcu()
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* or call_rcu() must be used to defer freeing until an RCU
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* grace period has elapsed.
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*/
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static inline void list_del_rcu(struct list_head *entry)
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{
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__list_del(entry->prev, entry->next);
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entry->prev = LIST_POISON2;
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}
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/**
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* hlist_del_init_rcu - deletes entry from hash list with re-initialization
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* @n: the element to delete from the hash list.
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*
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* Note: list_unhashed() on the node return true after this. It is
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* useful for RCU based read lockfree traversal if the writer side
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* must know if the list entry is still hashed or already unhashed.
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*
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* In particular, it means that we can not poison the forward pointers
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* that may still be used for walking the hash list and we can only
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* zero the pprev pointer so list_unhashed() will return true after
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* this.
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*
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* The caller must take whatever precautions are necessary (such as
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* holding appropriate locks) to avoid racing with another
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* list-mutation primitive, such as hlist_add_head_rcu() or
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* hlist_del_rcu(), running on this same list. However, it is
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* perfectly legal to run concurrently with the _rcu list-traversal
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* primitives, such as hlist_for_each_entry_rcu().
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*/
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static inline void hlist_del_init_rcu(struct hlist_node *n)
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{
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if (!hlist_unhashed(n)) {
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__hlist_del(n);
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n->pprev = NULL;
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}
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}
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/**
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* list_replace_rcu - replace old entry by new one
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* @old : the element to be replaced
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* @new : the new element to insert
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*
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* The @old entry will be replaced with the @new entry atomically.
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* Note: @old should not be empty.
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*/
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static inline void list_replace_rcu(struct list_head *old,
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struct list_head *new)
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{
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new->next = old->next;
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new->prev = old->prev;
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rcu_assign_pointer(new->prev->next, new);
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new->next->prev = new;
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old->prev = LIST_POISON2;
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}
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/**
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* list_splice_init_rcu - splice an RCU-protected list into an existing list.
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* @list: the RCU-protected list to splice
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* @head: the place in the list to splice the first list into
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* @sync: function to sync: synchronize_rcu(), synchronize_sched(), ...
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*
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* @head can be RCU-read traversed concurrently with this function.
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*
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* Note that this function blocks.
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*
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* Important note: the caller must take whatever action is necessary to
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* prevent any other updates to @head. In principle, it is possible
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* to modify the list as soon as sync() begins execution.
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* If this sort of thing becomes necessary, an alternative version
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* based on call_rcu() could be created. But only if -really-
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* needed -- there is no shortage of RCU API members.
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*/
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static inline void list_splice_init_rcu(struct list_head *list,
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struct list_head *head,
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void (*sync)(void))
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{
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struct list_head *first = list->next;
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struct list_head *last = list->prev;
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struct list_head *at = head->next;
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if (list_empty(head))
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return;
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/* "first" and "last" tracking list, so initialize it. */
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INIT_LIST_HEAD(list);
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/*
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* At this point, the list body still points to the source list.
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* Wait for any readers to finish using the list before splicing
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* the list body into the new list. Any new readers will see
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* an empty list.
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*/
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sync();
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/*
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* Readers are finished with the source list, so perform splice.
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* The order is important if the new list is global and accessible
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* to concurrent RCU readers. Note that RCU readers are not
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* permitted to traverse the prev pointers without excluding
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* this function.
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*/
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last->next = at;
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rcu_assign_pointer(head->next, first);
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first->prev = head;
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at->prev = last;
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}
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#define __list_for_each_rcu(pos, head) \
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for (pos = rcu_dereference((head)->next); \
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pos != (head); \
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pos = rcu_dereference(pos->next))
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/**
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* list_for_each_entry_rcu - iterate over rcu list of given type
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* @pos: the type * to use as a loop cursor.
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* @head: the head for your list.
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* @member: the name of the list_struct within the struct.
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*
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* This list-traversal primitive may safely run concurrently with
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* the _rcu list-mutation primitives such as list_add_rcu()
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* as long as the traversal is guarded by rcu_read_lock().
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*/
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#define list_for_each_entry_rcu(pos, head, member) \
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for (pos = list_entry(rcu_dereference((head)->next), typeof(*pos), member); \
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prefetch(pos->member.next), &pos->member != (head); \
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pos = list_entry(rcu_dereference(pos->member.next), typeof(*pos), member))
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/**
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* list_for_each_continue_rcu
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* @pos: the &struct list_head to use as a loop cursor.
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* @head: the head for your list.
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*
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* Iterate over an rcu-protected list, continuing after current point.
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*
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* This list-traversal primitive may safely run concurrently with
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* the _rcu list-mutation primitives such as list_add_rcu()
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* as long as the traversal is guarded by rcu_read_lock().
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*/
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#define list_for_each_continue_rcu(pos, head) \
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for ((pos) = rcu_dereference((pos)->next); \
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prefetch((pos)->next), (pos) != (head); \
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(pos) = rcu_dereference((pos)->next))
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/**
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* hlist_del_rcu - deletes entry from hash list without re-initialization
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* @n: the element to delete from the hash list.
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*
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* Note: list_unhashed() on entry does not return true after this,
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* the entry is in an undefined state. It is useful for RCU based
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* lockfree traversal.
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*
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* In particular, it means that we can not poison the forward
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* pointers that may still be used for walking the hash list.
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*
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* The caller must take whatever precautions are necessary
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* (such as holding appropriate locks) to avoid racing
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* with another list-mutation primitive, such as hlist_add_head_rcu()
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* or hlist_del_rcu(), running on this same list.
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* However, it is perfectly legal to run concurrently with
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* the _rcu list-traversal primitives, such as
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* hlist_for_each_entry().
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*/
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static inline void hlist_del_rcu(struct hlist_node *n)
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{
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__hlist_del(n);
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n->pprev = LIST_POISON2;
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}
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/**
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* hlist_replace_rcu - replace old entry by new one
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* @old : the element to be replaced
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* @new : the new element to insert
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*
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* The @old entry will be replaced with the @new entry atomically.
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*/
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static inline void hlist_replace_rcu(struct hlist_node *old,
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struct hlist_node *new)
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{
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struct hlist_node *next = old->next;
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new->next = next;
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new->pprev = old->pprev;
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rcu_assign_pointer(*new->pprev, new);
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if (next)
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new->next->pprev = &new->next;
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old->pprev = LIST_POISON2;
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}
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/**
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* hlist_add_head_rcu
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* @n: the element to add to the hash list.
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* @h: the list to add to.
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*
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* Description:
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* Adds the specified element to the specified hlist,
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* while permitting racing traversals.
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*
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* The caller must take whatever precautions are necessary
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* (such as holding appropriate locks) to avoid racing
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* with another list-mutation primitive, such as hlist_add_head_rcu()
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* or hlist_del_rcu(), running on this same list.
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* However, it is perfectly legal to run concurrently with
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* the _rcu list-traversal primitives, such as
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* hlist_for_each_entry_rcu(), used to prevent memory-consistency
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* problems on Alpha CPUs. Regardless of the type of CPU, the
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* list-traversal primitive must be guarded by rcu_read_lock().
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*/
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static inline void hlist_add_head_rcu(struct hlist_node *n,
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struct hlist_head *h)
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{
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struct hlist_node *first = h->first;
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n->next = first;
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n->pprev = &h->first;
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rcu_assign_pointer(h->first, n);
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if (first)
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first->pprev = &n->next;
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}
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/**
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* hlist_add_before_rcu
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* @n: the new element to add to the hash list.
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* @next: the existing element to add the new element before.
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*
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* Description:
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* Adds the specified element to the specified hlist
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* before the specified node while permitting racing traversals.
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*
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* The caller must take whatever precautions are necessary
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* (such as holding appropriate locks) to avoid racing
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* with another list-mutation primitive, such as hlist_add_head_rcu()
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* or hlist_del_rcu(), running on this same list.
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* However, it is perfectly legal to run concurrently with
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* the _rcu list-traversal primitives, such as
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* hlist_for_each_entry_rcu(), used to prevent memory-consistency
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* problems on Alpha CPUs.
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*/
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static inline void hlist_add_before_rcu(struct hlist_node *n,
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struct hlist_node *next)
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{
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n->pprev = next->pprev;
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n->next = next;
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rcu_assign_pointer(*(n->pprev), n);
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next->pprev = &n->next;
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}
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/**
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* hlist_add_after_rcu
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* @prev: the existing element to add the new element after.
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* @n: the new element to add to the hash list.
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*
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* Description:
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* Adds the specified element to the specified hlist
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* after the specified node while permitting racing traversals.
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*
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* The caller must take whatever precautions are necessary
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* (such as holding appropriate locks) to avoid racing
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* with another list-mutation primitive, such as hlist_add_head_rcu()
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* or hlist_del_rcu(), running on this same list.
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* However, it is perfectly legal to run concurrently with
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* the _rcu list-traversal primitives, such as
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* hlist_for_each_entry_rcu(), used to prevent memory-consistency
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* problems on Alpha CPUs.
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*/
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static inline void hlist_add_after_rcu(struct hlist_node *prev,
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struct hlist_node *n)
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{
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n->next = prev->next;
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n->pprev = &prev->next;
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rcu_assign_pointer(prev->next, n);
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if (n->next)
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n->next->pprev = &n->next;
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}
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/**
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* hlist_for_each_entry_rcu - iterate over rcu list of given type
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* @tpos: the type * to use as a loop cursor.
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* @pos: the &struct hlist_node to use as a loop cursor.
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* @head: the head for your list.
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* @member: the name of the hlist_node within the struct.
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*
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* This list-traversal primitive may safely run concurrently with
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* the _rcu list-mutation primitives such as hlist_add_head_rcu()
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* as long as the traversal is guarded by rcu_read_lock().
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*/
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#define hlist_for_each_entry_rcu(tpos, pos, head, member) \
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for (pos = rcu_dereference((head)->first); \
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pos && ({ prefetch(pos->next); 1; }) && \
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({ tpos = hlist_entry(pos, typeof(*tpos), member); 1; }); \
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pos = rcu_dereference(pos->next))
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#endif /* __KERNEL__ */
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#endif
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