rculist_bl.h
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#ifndef _LINUX_RCULIST_BL_H
#define _LINUX_RCULIST_BL_H
/*
* RCU-protected bl list version. See include/linux/list_bl.h.
*/
#include <linux/list_bl.h>
#include <linux/rcupdate.h>
static inline void hlist_bl_set_first_rcu(struct hlist_bl_head *h,
struct hlist_bl_node *n)
{
LIST_BL_BUG_ON((unsigned long)n & LIST_BL_LOCKMASK);
LIST_BL_BUG_ON(((unsigned long)h->first & LIST_BL_LOCKMASK) !=
LIST_BL_LOCKMASK);
rcu_assign_pointer(h->first,
(struct hlist_bl_node *)((unsigned long)n | LIST_BL_LOCKMASK));
}
static inline struct hlist_bl_node *hlist_bl_first_rcu(struct hlist_bl_head *h)
{
return (struct hlist_bl_node *)
((unsigned long)rcu_dereference_check(h->first, hlist_bl_is_locked(h)) & ~LIST_BL_LOCKMASK);
}
/**
* hlist_bl_del_init_rcu - deletes entry from hash list with re-initialization
* @n: the element to delete from the hash list.
*
* Note: hlist_bl_unhashed() on the node returns 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_bl_add_head_rcu() or
* hlist_bl_del_rcu(), running on this same list. However, it is
* perfectly legal to run concurrently with the _rcu list-traversal
* primitives, such as hlist_bl_for_each_entry_rcu().
*/
static inline void hlist_bl_del_init_rcu(struct hlist_bl_node *n)
{
if (!hlist_bl_unhashed(n)) {
__hlist_bl_del(n);
n->pprev = NULL;
}
}
/**
* hlist_bl_del_rcu - deletes entry from hash list without re-initialization
* @n: the element to delete from the hash list.
*
* Note: hlist_bl_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_bl_add_head_rcu()
* or hlist_bl_del_rcu(), running on this same list.
* However, it is perfectly legal to run concurrently with
* the _rcu list-traversal primitives, such as
* hlist_bl_for_each_entry().
*/
static inline void hlist_bl_del_rcu(struct hlist_bl_node *n)
{
__hlist_bl_del(n);
n->pprev = LIST_POISON2;
}
/**
* hlist_bl_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_bl,
* 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_bl_add_head_rcu()
* or hlist_bl_del_rcu(), running on this same list.
* However, it is perfectly legal to run concurrently with
* the _rcu list-traversal primitives, such as
* hlist_bl_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_bl_add_head_rcu(struct hlist_bl_node *n,
struct hlist_bl_head *h)
{
struct hlist_bl_node *first;
/* don't need hlist_bl_first_rcu because we're under lock */
first = hlist_bl_first(h);
n->next = first;
if (first)
first->pprev = &n->next;
n->pprev = &h->first;
/* need _rcu because we can have concurrent lock free readers */
hlist_bl_set_first_rcu(h, n);
}
/**
* hlist_bl_for_each_entry_rcu - iterate over rcu list of given type
* @tpos: the type * to use as a loop cursor.
* @pos: the &struct hlist_bl_node to use as a loop cursor.
* @head: the head for your list.
* @member: the name of the hlist_bl_node within the struct.
*
*/
#define hlist_bl_for_each_entry_rcu(tpos, pos, head, member) \
for (pos = hlist_bl_first_rcu(head); \
pos && \
({ tpos = hlist_bl_entry(pos, typeof(*tpos), member); 1; }); \
pos = rcu_dereference_raw(pos->next))
#endif