Contributors: 3
Author Tokens Token Proportion Commits Commit Proportion
Nicholas Piggin 191 83.77% 2 50.00%
Julian Anastasov 36 15.79% 1 25.00%
Greg Kroah-Hartman 1 0.44% 1 25.00%
Total 228 4 


/* SPDX-License-Identifier: GPL-2.0 */
#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>

/* return the first ptr or next element in an RCU protected list */
#define hlist_bl_first_rcu(head)	\
	(*((struct hlist_bl_node __rcu **)(&(head)->first)))
#define hlist_bl_next_rcu(node)	\
	(*((struct hlist_bl_node __rcu **)(&(node)->next)))

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(hlist_bl_first_rcu(h),
		(struct hlist_bl_node *)((unsigned long)n | LIST_BL_LOCKMASK));
}

#define hlist_bl_first_rcu_dereference(head)				\
({									\
	struct hlist_bl_head *__head = (head);				\
									\
	(struct hlist_bl_node *)					\
	((unsigned long)rcu_dereference_check(hlist_bl_first_rcu(__head), \
					      hlist_bl_is_locked(__head)) & \
					      ~LIST_BL_LOCKMASK);	\
})

/**
 * 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_dereference(head);		\
		pos &&							\
		({ tpos = hlist_bl_entry(pos, typeof(*tpos), member); 1; }); \
		pos = rcu_dereference_raw(hlist_bl_next_rcu(pos)))

/**
 * hlist_bl_for_each_entry_continue_rcu - continue iteration over 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.
 * @member:	the name of the hlist_bl_node 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.
 */
#define hlist_bl_for_each_entry_continue_rcu(tpos, pos, member)		\
	for (pos = rcu_dereference_raw(hlist_bl_next_rcu(&(tpos)->member)); \
	     pos &&							\
	     ({ tpos = hlist_bl_entry(pos, typeof(*tpos), member); 1; }); \
	     pos = rcu_dereference_raw(hlist_bl_next_rcu(pos)))

#endif