diff --git a/include/linux/list_nulls.h b/include/linux/list_nulls.h new file mode 100644 index 0000000..856dee8 --- /dev/null +++ b/include/linux/list_nulls.h @@ -0,0 +1,94 @@ +#ifndef _LINUX_LIST_NULLS_H +#define _LINUX_LIST_NULLS_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 INIT_HLIST_NULLS_HEAD(ptr, nulls) \ + ((ptr)->first = (struct hlist_nulls_node *) (1UL | (((long)nulls) << 1))) + +#define hlist_nulls_entry(ptr, type, member) container_of(ptr,type,member) +/** + * 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; +} + +static inline int hlist_nulls_unhashed(const struct hlist_nulls_node *h) +{ + return !h->pprev; +} + +static inline int hlist_nulls_empty(const struct hlist_nulls_head *h) +{ + return is_a_nulls(h->first); +} + +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; + *pprev = next; + if (!is_a_nulls(next)) + next->pprev = pprev; +} + +/** + * 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 diff --git a/include/linux/rculist_nulls.h b/include/linux/rculist_nulls.h new file mode 100644 index 0000000..b185ac4 --- /dev/null +++ b/include/linux/rculist_nulls.h @@ -0,0 +1,110 @@ +#ifndef _LINUX_RCULIST_NULLS_H +#define _LINUX_RCULIST_NULLS_H + +#ifdef __KERNEL__ + +/* + * RCU-protected list version + */ +#include +#include + +/** + * hlist_nulls_del_init_rcu - deletes entry from hash list with re-initialization + * @n: the element to delete from the hash list. + * + * Note: hlist_nulls_unhashed() on the node return true after this. It is + * useful for RCU based read lockfree traversal if the writer side + * must know if the list entry is still hashed or already unhashed. + * + * In particular, it means that we can not poison the forward pointers + * that may still be used for walking the hash list and we can only + * zero the pprev pointer so list_unhashed() will return true after + * this. + * + * The caller must take whatever precautions are necessary (such as + * holding appropriate locks) to avoid racing with another + * list-mutation primitive, such as hlist_nulls_add_head_rcu() or + * hlist_nulls_del_rcu(), running on this same list. However, it is + * perfectly legal to run concurrently with the _rcu list-traversal + * primitives, such as hlist_nulls_for_each_entry_rcu(). + */ +static inline void hlist_nulls_del_init_rcu(struct hlist_nulls_node *n) +{ + if (!hlist_nulls_unhashed(n)) { + __hlist_nulls_del(n); + n->pprev = NULL; + } +} + +/** + * hlist_nulls_del_rcu - deletes entry from hash list without re-initialization + * @n: the element to delete from the hash list. + * + * Note: hlist_nulls_unhashed() on entry does not return true after this, + * the entry is in an undefined state. It is useful for RCU based + * lockfree traversal. + * + * In particular, it means that we can not poison the forward + * pointers that may still be used for walking the hash list. + * + * The caller must take whatever precautions are necessary + * (such as holding appropriate locks) to avoid racing + * with another list-mutation primitive, such as hlist_nulls_add_head_rcu() + * or hlist_nulls_del_rcu(), running on this same list. + * However, it is perfectly legal to run concurrently with + * the _rcu list-traversal primitives, such as + * hlist_nulls_for_each_entry(). + */ +static inline void hlist_nulls_del_rcu(struct hlist_nulls_node *n) +{ + __hlist_nulls_del(n); + n->pprev = LIST_POISON2; +} + +/** + * hlist_nulls_add_head_rcu + * @n: the element to add to the hash list. + * @h: the list to add to. + * + * Description: + * Adds the specified element to the specified hlist_nulls, + * while permitting racing traversals. + * + * The caller must take whatever precautions are necessary + * (such as holding appropriate locks) to avoid racing + * with another list-mutation primitive, such as hlist_nulls_add_head_rcu() + * or hlist_nulls_del_rcu(), running on this same list. + * However, it is perfectly legal to run concurrently with + * the _rcu list-traversal primitives, such as + * hlist_nulls_for_each_entry_rcu(), used to prevent memory-consistency + * problems on Alpha CPUs. Regardless of the type of CPU, the + * list-traversal primitive must be guarded by rcu_read_lock(). + */ +static inline void hlist_nulls_add_head_rcu(struct hlist_nulls_node *n, + struct hlist_nulls_head *h) +{ + struct hlist_nulls_node *first = h->first; + + n->next = first; + n->pprev = &h->first; + rcu_assign_pointer(h->first, n); + if (!is_a_nulls(first)) + first->pprev = &n->next; +} +/** + * hlist_nulls_for_each_entry_rcu - iterate over rcu list of given type + * @tpos: the type * to use as a loop cursor. + * @pos: the &struct hlist_nulls_node to use as a loop cursor. + * @head: the head for your list. + * @member: the name of the hlist_nulls_node within the struct. + * + */ +#define hlist_nulls_for_each_entry_rcu(tpos, pos, head, member) \ + for (pos = rcu_dereference((head)->first); \ + (!is_a_nulls(pos)) && \ + ({ tpos = hlist_nulls_entry(pos, typeof(*tpos), member); 1; }); \ + pos = rcu_dereference(pos->next)) + +#endif +#endif