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 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 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_check(h->first, hlist_bl_is_locked(h)) & ~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 */ 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 */ 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 */ 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