111 lines
3.8 KiB
C
111 lines
3.8 KiB
C
#ifndef _LINUX_RCULIST_NULLS_H
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#define _LINUX_RCULIST_NULLS_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_nulls.h>
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#include <linux/rcupdate.h>
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/**
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* hlist_nulls_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: hlist_nulls_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_nulls_add_head_rcu() or
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* hlist_nulls_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_nulls_for_each_entry_rcu().
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*/
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static inline void hlist_nulls_del_init_rcu(struct hlist_nulls_node *n)
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{
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if (!hlist_nulls_unhashed(n)) {
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__hlist_nulls_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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* hlist_nulls_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: hlist_nulls_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_nulls_add_head_rcu()
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* or hlist_nulls_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_nulls_for_each_entry().
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*/
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static inline void hlist_nulls_del_rcu(struct hlist_nulls_node *n)
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{
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__hlist_nulls_del(n);
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n->pprev = LIST_POISON2;
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}
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/**
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* hlist_nulls_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_nulls,
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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_nulls_add_head_rcu()
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* or hlist_nulls_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_nulls_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_nulls_add_head_rcu(struct hlist_nulls_node *n,
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struct hlist_nulls_head *h)
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{
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struct hlist_nulls_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 (!is_a_nulls(first))
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first->pprev = &n->next;
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}
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/**
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* hlist_nulls_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_nulls_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_nulls_node within the struct.
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*
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*/
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#define hlist_nulls_for_each_entry_rcu(tpos, pos, head, member) \
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for (pos = rcu_dereference((head)->first); \
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(!is_a_nulls(pos)) && \
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({ tpos = hlist_nulls_entry(pos, typeof(*tpos), member); 1; }); \
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pos = rcu_dereference(pos->next))
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#endif
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#endif
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