1 #ifndef _LINUX_RCULIST_BL_H
2 #define _LINUX_RCULIST_BL_H
3 
4 /*
5  * RCU-protected bl list version. See include/linux/list_bl.h.
6  */
7 #include <linux/list_bl.h>
8 #include <linux/rcupdate.h>
9 
hlist_bl_set_first_rcu(struct hlist_bl_head * h,struct hlist_bl_node * n)10 static inline void hlist_bl_set_first_rcu(struct hlist_bl_head *h,
11 					struct hlist_bl_node *n)
12 {
13 	LIST_BL_BUG_ON((unsigned long)n & LIST_BL_LOCKMASK);
14 	LIST_BL_BUG_ON(((unsigned long)h->first & LIST_BL_LOCKMASK) !=
15 							LIST_BL_LOCKMASK);
16 	rcu_assign_pointer(h->first,
17 		(struct hlist_bl_node *)((unsigned long)n | LIST_BL_LOCKMASK));
18 }
19 
hlist_bl_first_rcu(struct hlist_bl_head * h)20 static inline struct hlist_bl_node *hlist_bl_first_rcu(struct hlist_bl_head *h)
21 {
22 	return (struct hlist_bl_node *)
23 		((unsigned long)rcu_dereference(h->first) & ~LIST_BL_LOCKMASK);
24 }
25 
26 /**
27  * hlist_bl_del_init_rcu - deletes entry from hash list with re-initialization
28  * @n: the element to delete from the hash list.
29  *
30  * Note: hlist_bl_unhashed() on the node returns true after this. It is
31  * useful for RCU based read lockfree traversal if the writer side
32  * must know if the list entry is still hashed or already unhashed.
33  *
34  * In particular, it means that we can not poison the forward pointers
35  * that may still be used for walking the hash list and we can only
36  * zero the pprev pointer so list_unhashed() will return true after
37  * this.
38  *
39  * The caller must take whatever precautions are necessary (such as
40  * holding appropriate locks) to avoid racing with another
41  * list-mutation primitive, such as hlist_bl_add_head_rcu() or
42  * hlist_bl_del_rcu(), running on this same list.  However, it is
43  * perfectly legal to run concurrently with the _rcu list-traversal
44  * primitives, such as hlist_bl_for_each_entry_rcu().
45  */
hlist_bl_del_init_rcu(struct hlist_bl_node * n)46 static inline void hlist_bl_del_init_rcu(struct hlist_bl_node *n)
47 {
48 	if (!hlist_bl_unhashed(n)) {
49 		__hlist_bl_del(n);
50 		n->pprev = NULL;
51 	}
52 }
53 
54 /**
55  * hlist_bl_del_rcu - deletes entry from hash list without re-initialization
56  * @n: the element to delete from the hash list.
57  *
58  * Note: hlist_bl_unhashed() on entry does not return true after this,
59  * the entry is in an undefined state. It is useful for RCU based
60  * lockfree traversal.
61  *
62  * In particular, it means that we can not poison the forward
63  * pointers that may still be used for walking the hash list.
64  *
65  * The caller must take whatever precautions are necessary
66  * (such as holding appropriate locks) to avoid racing
67  * with another list-mutation primitive, such as hlist_bl_add_head_rcu()
68  * or hlist_bl_del_rcu(), running on this same list.
69  * However, it is perfectly legal to run concurrently with
70  * the _rcu list-traversal primitives, such as
71  * hlist_bl_for_each_entry().
72  */
hlist_bl_del_rcu(struct hlist_bl_node * n)73 static inline void hlist_bl_del_rcu(struct hlist_bl_node *n)
74 {
75 	__hlist_bl_del(n);
76 	n->pprev = LIST_POISON2;
77 }
78 
79 /**
80  * hlist_bl_add_head_rcu
81  * @n: the element to add to the hash list.
82  * @h: the list to add to.
83  *
84  * Description:
85  * Adds the specified element to the specified hlist_bl,
86  * while permitting racing traversals.
87  *
88  * The caller must take whatever precautions are necessary
89  * (such as holding appropriate locks) to avoid racing
90  * with another list-mutation primitive, such as hlist_bl_add_head_rcu()
91  * or hlist_bl_del_rcu(), running on this same list.
92  * However, it is perfectly legal to run concurrently with
93  * the _rcu list-traversal primitives, such as
94  * hlist_bl_for_each_entry_rcu(), used to prevent memory-consistency
95  * problems on Alpha CPUs.  Regardless of the type of CPU, the
96  * list-traversal primitive must be guarded by rcu_read_lock().
97  */
hlist_bl_add_head_rcu(struct hlist_bl_node * n,struct hlist_bl_head * h)98 static inline void hlist_bl_add_head_rcu(struct hlist_bl_node *n,
99 					struct hlist_bl_head *h)
100 {
101 	struct hlist_bl_node *first;
102 
103 	/* don't need hlist_bl_first_rcu because we're under lock */
104 	first = hlist_bl_first(h);
105 
106 	n->next = first;
107 	if (first)
108 		first->pprev = &n->next;
109 	n->pprev = &h->first;
110 
111 	/* need _rcu because we can have concurrent lock free readers */
112 	hlist_bl_set_first_rcu(h, n);
113 }
114 /**
115  * hlist_bl_for_each_entry_rcu - iterate over rcu list of given type
116  * @tpos:	the type * to use as a loop cursor.
117  * @pos:	the &struct hlist_bl_node to use as a loop cursor.
118  * @head:	the head for your list.
119  * @member:	the name of the hlist_bl_node within the struct.
120  *
121  */
122 #define hlist_bl_for_each_entry_rcu(tpos, pos, head, member)		\
123 	for (pos = hlist_bl_first_rcu(head);				\
124 		pos &&							\
125 		({ tpos = hlist_bl_entry(pos, typeof(*tpos), member); 1; }); \
126 		pos = rcu_dereference_raw(pos->next))
127 
128 #endif
129