127 lines
4.6 KiB
C
127 lines
4.6 KiB
C
#ifndef LLIST_H
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#define LLIST_H
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/*
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* Lock-less NULL terminated single linked list
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*
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* If there are multiple producers and multiple consumers, llist_add
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* can be used in producers and llist_del_all can be used in
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* consumers. They can work simultaneously without lock. But
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* llist_del_first can not be used here. Because llist_del_first
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* depends on list->first->next does not changed if list->first is not
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* changed during its operation, but llist_del_first, llist_add,
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* llist_add (or llist_del_all, llist_add, llist_add) sequence in
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* another consumer may violate that.
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*
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* If there are multiple producers and one consumer, llist_add can be
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* used in producers and llist_del_all or llist_del_first can be used
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* in the consumer.
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*
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* This can be summarized as follow:
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*
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* | add | del_first | del_all
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* add | - | - | -
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* del_first | | L | L
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* del_all | | | -
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*
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* Where "-" stands for no lock is needed, while "L" stands for lock
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* is needed.
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*
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* The list entries deleted via llist_del_all can be traversed with
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* traversing function such as llist_for_each etc. But the list
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* entries can not be traversed safely before deleted from the list.
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* The order of deleted entries is from the newest to the oldest added
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* one. If you want to traverse from the oldest to the newest, you
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* must reverse the order by yourself before traversing.
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*
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* The basic atomic operation of this list is cmpxchg on long. On
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* architectures that don't have NMI-safe cmpxchg implementation, the
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* list can NOT be used in NMI handler. So code uses the list in NMI
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* handler should depend on CONFIG_ARCH_HAVE_NMI_SAFE_CMPXCHG.
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*/
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struct llist_head {
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struct llist_node *first;
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};
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struct llist_node {
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struct llist_node *next;
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};
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#define LLIST_HEAD_INIT(name) { NULL }
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#define LLIST_HEAD(name) struct llist_head name = LLIST_HEAD_INIT(name)
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/**
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* init_llist_head - initialize lock-less list head
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* @head: the head for your lock-less list
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*/
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static inline void init_llist_head(struct llist_head *list)
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{
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list->first = NULL;
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}
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/**
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* llist_entry - get the struct of this entry
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* @ptr: the &struct llist_node pointer.
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* @type: the type of the struct this is embedded in.
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* @member: the name of the llist_node within the struct.
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*/
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#define llist_entry(ptr, type, member) \
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container_of(ptr, type, member)
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/**
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* llist_for_each - iterate over some deleted entries of a lock-less list
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* @pos: the &struct llist_node to use as a loop cursor
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* @node: the first entry of deleted list entries
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*
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* In general, some entries of the lock-less list can be traversed
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* safely only after being deleted from list, so start with an entry
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* instead of list head.
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*
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* If being used on entries deleted from lock-less list directly, the
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* traverse order is from the newest to the oldest added entry. If
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* you want to traverse from the oldest to the newest, you must
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* reverse the order by yourself before traversing.
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*/
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#define llist_for_each(pos, node) \
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for ((pos) = (node); pos; (pos) = (pos)->next)
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/**
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* llist_for_each_entry - iterate over some deleted entries of lock-less list of given type
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* @pos: the type * to use as a loop cursor.
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* @node: the fist entry of deleted list entries.
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* @member: the name of the llist_node with the struct.
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*
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* In general, some entries of the lock-less list can be traversed
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* safely only after being removed from list, so start with an entry
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* instead of list head.
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*
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* If being used on entries deleted from lock-less list directly, the
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* traverse order is from the newest to the oldest added entry. If
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* you want to traverse from the oldest to the newest, you must
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* reverse the order by yourself before traversing.
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*/
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#define llist_for_each_entry(pos, node, member) \
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for ((pos) = llist_entry((node), typeof(*(pos)), member); \
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&(pos)->member != NULL; \
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(pos) = llist_entry((pos)->member.next, typeof(*(pos)), member))
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/**
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* llist_empty - tests whether a lock-less list is empty
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* @head: the list to test
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*
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* Not guaranteed to be accurate or up to date. Just a quick way to
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* test whether the list is empty without deleting something from the
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* list.
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*/
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static inline int llist_empty(const struct llist_head *head)
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{
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return ACCESS_ONCE(head->first) == NULL;
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}
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void llist_add(struct llist_node *new, struct llist_head *head);
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void llist_add_batch(struct llist_node *new_first, struct llist_node *new_last,
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struct llist_head *head);
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struct llist_node *llist_del_first(struct llist_head *head);
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struct llist_node *llist_del_all(struct llist_head *head);
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#endif /* LLIST_H */
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