| /* SPDX-License-Identifier: GPL-2.0 */ |
| #ifndef _LINUX_LIST_NULLS_H |
| #define _LINUX_LIST_NULLS_H |
| |
| #include <linux/poison.h> |
| #include <linux/const.h> |
| |
| /* |
| * Special version of lists, where end of list is not a NULL pointer, |
| * but a 'nulls' marker, which can have many different values. |
| * (up to 2^31 different values guaranteed on all platforms) |
| * |
| * In the standard hlist, termination of a list is the NULL pointer. |
| * In this special 'nulls' variant, we use the fact that objects stored in |
| * a list are aligned on a word (4 or 8 bytes alignment). |
| * We therefore use the last significant bit of 'ptr' : |
| * Set to 1 : This is a 'nulls' end-of-list marker (ptr >> 1) |
| * Set to 0 : This is a pointer to some object (ptr) |
| */ |
| |
| struct hlist_nulls_head { |
| struct hlist_nulls_node *first; |
| }; |
| |
| struct hlist_nulls_node { |
| struct hlist_nulls_node *next, **pprev; |
| }; |
| #define NULLS_MARKER(value) (1UL | (((long)value) << 1)) |
| #define INIT_HLIST_NULLS_HEAD(ptr, nulls) \ |
| ((ptr)->first = (struct hlist_nulls_node *) NULLS_MARKER(nulls)) |
| |
| #define hlist_nulls_entry(ptr, type, member) container_of(ptr,type,member) |
| |
| #define hlist_nulls_entry_safe(ptr, type, member) \ |
| ({ typeof(ptr) ____ptr = (ptr); \ |
| !is_a_nulls(____ptr) ? hlist_nulls_entry(____ptr, type, member) : NULL; \ |
| }) |
| /** |
| * ptr_is_a_nulls - Test if a ptr is a nulls |
| * @ptr: ptr to be tested |
| * |
| */ |
| static inline int is_a_nulls(const struct hlist_nulls_node *ptr) |
| { |
| return ((unsigned long)ptr & 1); |
| } |
| |
| /** |
| * get_nulls_value - Get the 'nulls' value of the end of chain |
| * @ptr: end of chain |
| * |
| * Should be called only if is_a_nulls(ptr); |
| */ |
| static inline unsigned long get_nulls_value(const struct hlist_nulls_node *ptr) |
| { |
| return ((unsigned long)ptr) >> 1; |
| } |
| |
| /** |
| * hlist_nulls_unhashed - Has node been removed and reinitialized? |
| * @h: Node to be checked |
| * |
| * Not that not all removal functions will leave a node in unhashed state. |
| * For example, hlist_del_init_rcu() leaves the node in unhashed state, |
| * but hlist_nulls_del() does not. |
| */ |
| static inline int hlist_nulls_unhashed(const struct hlist_nulls_node *h) |
| { |
| return !h->pprev; |
| } |
| |
| /** |
| * hlist_nulls_unhashed_lockless - Has node been removed and reinitialized? |
| * @h: Node to be checked |
| * |
| * Not that not all removal functions will leave a node in unhashed state. |
| * For example, hlist_del_init_rcu() leaves the node in unhashed state, |
| * but hlist_nulls_del() does not. Unlike hlist_nulls_unhashed(), this |
| * function may be used locklessly. |
| */ |
| static inline int hlist_nulls_unhashed_lockless(const struct hlist_nulls_node *h) |
| { |
| return !READ_ONCE(h->pprev); |
| } |
| |
| static inline int hlist_nulls_empty(const struct hlist_nulls_head *h) |
| { |
| return is_a_nulls(READ_ONCE(h->first)); |
| } |
| |
| static inline void hlist_nulls_add_head(struct hlist_nulls_node *n, |
| struct hlist_nulls_head *h) |
| { |
| struct hlist_nulls_node *first = h->first; |
| |
| n->next = first; |
| WRITE_ONCE(n->pprev, &h->first); |
| h->first = n; |
| if (!is_a_nulls(first)) |
| WRITE_ONCE(first->pprev, &n->next); |
| } |
| |
| static inline void __hlist_nulls_del(struct hlist_nulls_node *n) |
| { |
| struct hlist_nulls_node *next = n->next; |
| struct hlist_nulls_node **pprev = n->pprev; |
| |
| WRITE_ONCE(*pprev, next); |
| if (!is_a_nulls(next)) |
| WRITE_ONCE(next->pprev, pprev); |
| } |
| |
| static inline void hlist_nulls_del(struct hlist_nulls_node *n) |
| { |
| __hlist_nulls_del(n); |
| WRITE_ONCE(n->pprev, LIST_POISON2); |
| } |
| |
| /** |
| * hlist_nulls_for_each_entry - iterate over list of given type |
| * @tpos: the type * to use as a loop cursor. |
| * @pos: the &struct hlist_node to use as a loop cursor. |
| * @head: the head for your list. |
| * @member: the name of the hlist_node within the struct. |
| * |
| */ |
| #define hlist_nulls_for_each_entry(tpos, pos, head, member) \ |
| for (pos = (head)->first; \ |
| (!is_a_nulls(pos)) && \ |
| ({ tpos = hlist_nulls_entry(pos, typeof(*tpos), member); 1;}); \ |
| pos = pos->next) |
| |
| /** |
| * hlist_nulls_for_each_entry_from - iterate over a hlist continuing from current point |
| * @tpos: the type * to use as a loop cursor. |
| * @pos: the &struct hlist_node to use as a loop cursor. |
| * @member: the name of the hlist_node within the struct. |
| * |
| */ |
| #define hlist_nulls_for_each_entry_from(tpos, pos, member) \ |
| for (; (!is_a_nulls(pos)) && \ |
| ({ tpos = hlist_nulls_entry(pos, typeof(*tpos), member); 1;}); \ |
| pos = pos->next) |
| |
| #endif |