1 #ifndef _LINUX_LIST_NULLS_H 2 #define _LINUX_LIST_NULLS_H 3 4 /* 5 * Special version of lists, where end of list is not a NULL pointer, 6 * but a 'nulls' marker, which can have many different values. 7 * (up to 2^31 different values guaranteed on all platforms) 8 * 9 * In the standard hlist, termination of a list is the NULL pointer. 10 * In this special 'nulls' variant, we use the fact that objects stored in 11 * a list are aligned on a word (4 or 8 bytes alignment). 12 * We therefore use the last significant bit of 'ptr' : 13 * Set to 1 : This is a 'nulls' end-of-list marker (ptr >> 1) 14 * Set to 0 : This is a pointer to some object (ptr) 15 */ 16 17 struct hlist_nulls_head { 18 struct hlist_nulls_node *first; 19 }; 20 21 struct hlist_nulls_node { 22 struct hlist_nulls_node *next, **pprev; 23 }; 24 #define NULLS_MARKER(value) (1UL | (((long)value) << 1)) 25 #define INIT_HLIST_NULLS_HEAD(ptr, nulls) \ 26 ((ptr)->first = (struct hlist_nulls_node *) NULLS_MARKER(nulls)) 27 28 #define hlist_nulls_entry(ptr, type, member) container_of(ptr,type,member) 29 /** 30 * ptr_is_a_nulls - Test if a ptr is a nulls 31 * @ptr: ptr to be tested 32 * 33 */ 34 static inline int is_a_nulls(const struct hlist_nulls_node *ptr) 35 { 36 return ((unsigned long)ptr & 1); 37 } 38 39 /** 40 * get_nulls_value - Get the 'nulls' value of the end of chain 41 * @ptr: end of chain 42 * 43 * Should be called only if is_a_nulls(ptr); 44 */ 45 static inline unsigned long get_nulls_value(const struct hlist_nulls_node *ptr) 46 { 47 return ((unsigned long)ptr) >> 1; 48 } 49 50 static inline int hlist_nulls_unhashed(const struct hlist_nulls_node *h) 51 { 52 return !h->pprev; 53 } 54 55 static inline int hlist_nulls_empty(const struct hlist_nulls_head *h) 56 { 57 return is_a_nulls(h->first); 58 } 59 60 static inline void hlist_nulls_add_head(struct hlist_nulls_node *n, 61 struct hlist_nulls_head *h) 62 { 63 struct hlist_nulls_node *first = h->first; 64 65 n->next = first; 66 n->pprev = &h->first; 67 h->first = n; 68 if (!is_a_nulls(first)) 69 first->pprev = &n->next; 70 } 71 72 static inline void __hlist_nulls_del(struct hlist_nulls_node *n) 73 { 74 struct hlist_nulls_node *next = n->next; 75 struct hlist_nulls_node **pprev = n->pprev; 76 *pprev = next; 77 if (!is_a_nulls(next)) 78 next->pprev = pprev; 79 } 80 81 static inline void hlist_nulls_del(struct hlist_nulls_node *n) 82 { 83 __hlist_nulls_del(n); 84 n->pprev = LIST_POISON2; 85 } 86 87 /** 88 * hlist_nulls_for_each_entry - iterate over list of given type 89 * @tpos: the type * to use as a loop cursor. 90 * @pos: the &struct hlist_node to use as a loop cursor. 91 * @head: the head for your list. 92 * @member: the name of the hlist_node within the struct. 93 * 94 */ 95 #define hlist_nulls_for_each_entry(tpos, pos, head, member) \ 96 for (pos = (head)->first; \ 97 (!is_a_nulls(pos)) && \ 98 ({ tpos = hlist_nulls_entry(pos, typeof(*tpos), member); 1;}); \ 99 pos = pos->next) 100 101 /** 102 * hlist_nulls_for_each_entry_from - iterate over a hlist continuing from current point 103 * @tpos: the type * to use as a loop cursor. 104 * @pos: the &struct hlist_node to use as a loop cursor. 105 * @member: the name of the hlist_node within the struct. 106 * 107 */ 108 #define hlist_nulls_for_each_entry_from(tpos, pos, member) \ 109 for (; (!is_a_nulls(pos)) && \ 110 ({ tpos = hlist_nulls_entry(pos, typeof(*tpos), member); 1;}); \ 111 pos = pos->next) 112 113 #endif 114