1 /* SPDX-License-Identifier: GPL-2.0 */ 2 #ifndef _LINUX_RCULIST_BL_H 3 #define _LINUX_RCULIST_BL_H 4 5 /* 6 * RCU-protected bl list version. See include/linux/list_bl.h. 7 */ 8 #include <linux/list_bl.h> 9 #include <linux/rcupdate.h> 10 11 static inline void hlist_bl_set_first_rcu(struct hlist_bl_head *h, 12 struct hlist_bl_node *n) 13 { 14 LIST_BL_BUG_ON((unsigned long)n & LIST_BL_LOCKMASK); 15 LIST_BL_BUG_ON(((unsigned long)h->first & LIST_BL_LOCKMASK) != 16 LIST_BL_LOCKMASK); 17 rcu_assign_pointer(h->first, 18 (struct hlist_bl_node *)((unsigned long)n | LIST_BL_LOCKMASK)); 19 } 20 21 static inline struct hlist_bl_node *hlist_bl_first_rcu(struct hlist_bl_head *h) 22 { 23 return (struct hlist_bl_node *) 24 ((unsigned long)rcu_dereference_check(h->first, hlist_bl_is_locked(h)) & ~LIST_BL_LOCKMASK); 25 } 26 27 /** 28 * hlist_bl_del_init_rcu - deletes entry from hash list with re-initialization 29 * @n: the element to delete from the hash list. 30 * 31 * Note: hlist_bl_unhashed() on the node returns true after this. It is 32 * useful for RCU based read lockfree traversal if the writer side 33 * must know if the list entry is still hashed or already unhashed. 34 * 35 * In particular, it means that we can not poison the forward pointers 36 * that may still be used for walking the hash list and we can only 37 * zero the pprev pointer so list_unhashed() will return true after 38 * this. 39 * 40 * The caller must take whatever precautions are necessary (such as 41 * holding appropriate locks) to avoid racing with another 42 * list-mutation primitive, such as hlist_bl_add_head_rcu() or 43 * hlist_bl_del_rcu(), running on this same list. However, it is 44 * perfectly legal to run concurrently with the _rcu list-traversal 45 * primitives, such as hlist_bl_for_each_entry_rcu(). 46 */ 47 static inline void hlist_bl_del_init_rcu(struct hlist_bl_node *n) 48 { 49 if (!hlist_bl_unhashed(n)) { 50 __hlist_bl_del(n); 51 n->pprev = NULL; 52 } 53 } 54 55 /** 56 * hlist_bl_del_rcu - deletes entry from hash list without re-initialization 57 * @n: the element to delete from the hash list. 58 * 59 * Note: hlist_bl_unhashed() on entry does not return true after this, 60 * the entry is in an undefined state. It is useful for RCU based 61 * lockfree traversal. 62 * 63 * In particular, it means that we can not poison the forward 64 * pointers that may still be used for walking the hash list. 65 * 66 * The caller must take whatever precautions are necessary 67 * (such as holding appropriate locks) to avoid racing 68 * with another list-mutation primitive, such as hlist_bl_add_head_rcu() 69 * or hlist_bl_del_rcu(), running on this same list. 70 * However, it is perfectly legal to run concurrently with 71 * the _rcu list-traversal primitives, such as 72 * hlist_bl_for_each_entry(). 73 */ 74 static inline void hlist_bl_del_rcu(struct hlist_bl_node *n) 75 { 76 __hlist_bl_del(n); 77 n->pprev = LIST_POISON2; 78 } 79 80 /** 81 * hlist_bl_add_head_rcu 82 * @n: the element to add to the hash list. 83 * @h: the list to add to. 84 * 85 * Description: 86 * Adds the specified element to the specified hlist_bl, 87 * while permitting racing traversals. 88 * 89 * The caller must take whatever precautions are necessary 90 * (such as holding appropriate locks) to avoid racing 91 * with another list-mutation primitive, such as hlist_bl_add_head_rcu() 92 * or hlist_bl_del_rcu(), running on this same list. 93 * However, it is perfectly legal to run concurrently with 94 * the _rcu list-traversal primitives, such as 95 * hlist_bl_for_each_entry_rcu(), used to prevent memory-consistency 96 * problems on Alpha CPUs. Regardless of the type of CPU, the 97 * list-traversal primitive must be guarded by rcu_read_lock(). 98 */ 99 static inline void hlist_bl_add_head_rcu(struct hlist_bl_node *n, 100 struct hlist_bl_head *h) 101 { 102 struct hlist_bl_node *first; 103 104 /* don't need hlist_bl_first_rcu because we're under lock */ 105 first = hlist_bl_first(h); 106 107 n->next = first; 108 if (first) 109 first->pprev = &n->next; 110 n->pprev = &h->first; 111 112 /* need _rcu because we can have concurrent lock free readers */ 113 hlist_bl_set_first_rcu(h, n); 114 } 115 /** 116 * hlist_bl_for_each_entry_rcu - iterate over rcu list of given type 117 * @tpos: the type * to use as a loop cursor. 118 * @pos: the &struct hlist_bl_node to use as a loop cursor. 119 * @head: the head for your list. 120 * @member: the name of the hlist_bl_node within the struct. 121 * 122 */ 123 #define hlist_bl_for_each_entry_rcu(tpos, pos, head, member) \ 124 for (pos = hlist_bl_first_rcu(head); \ 125 pos && \ 126 ({ tpos = hlist_bl_entry(pos, typeof(*tpos), member); 1; }); \ 127 pos = rcu_dereference_raw(pos->next)) 128 129 #endif 130