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