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MINOR: mt_lists: Add new macroes.
Add a few new macroes to the mt_lists. MT_LIST_LOCK_ELT()/MT_LIST_UNLOCK_ELT() helps locking/unlocking an element. This should only be used if you know for sure nobody else will remove the element from the list in the meanwhile. mt_list_for_each_entry_safe() is an iterator, similar to list_for_each_entry_safe(). It takes 5 arguments, item, list_head, member are similar to those of the non-mt variant, tmpelt is a temporary pointer to a struct mt_list, while tmpelt2 is a struct mt_list itself. MT_LIST_DEL_SELF() can be used to delete an item while parsing the list with mt_list_for_each_entry_safe(). It shouldn't be used outside, and you shouldn't use MT_LIST_DEL() while using mt_list_for_each_entry_safe().
This commit is contained in:
Olivier Houchard
Olivier Houchard
parent
859dc80f94
commit
5e9b92cbff
@ -388,4 +388,180 @@ struct cond_wordlist {
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*/
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#define MT_LIST_ADDED(el) ((el)->next != (el))
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/* Lock an element in the list, to be sure it won't be removed.
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* It needs to be synchronized somehow to be sure it's not removed
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* from the list in the meanwhile.
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* This returns a struct mt_list, that will be needed at unlock time.
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*/
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#define MT_LIST_LOCK_ELT(el) \
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({ \
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struct mt_list ret; \
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while (1) { \
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struct mt_list *n, *n2; \
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struct mt_list *p, *p2 = NULL; \
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n = _HA_ATOMIC_XCHG(&(el)->next, MT_LIST_BUSY); \
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if (n == MT_LIST_BUSY) \
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continue; \
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p = _HA_ATOMIC_XCHG(&(el)->prev, MT_LIST_BUSY); \
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if (p == MT_LIST_BUSY) { \
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(el)->next = n; \
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__ha_barrier_store(); \
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continue; \
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} \
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if (p != (el)) { \
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p2 = _HA_ATOMIC_XCHG(&p->next, MT_LIST_BUSY);\
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if (p2 == MT_LIST_BUSY) { \
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(el)->prev = p; \
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(el)->next = n; \
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__ha_barrier_store(); \
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continue; \
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} \
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} \
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if (n != (el)) { \
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n2 = _HA_ATOMIC_XCHG(&n->prev, MT_LIST_BUSY);\
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if (n2 == MT_LIST_BUSY) { \
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if (p2 != NULL) \
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p->next = p2; \
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(el)->prev = p; \
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(el)->next = n; \
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__ha_barrier_store(); \
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continue; \
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} \
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} \
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ret.next = n; \
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ret.prev = p; \
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break; \
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} \
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ret; \
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})
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/* Unlock an element previously locked by MT_LIST_LOCK_ELT. "np" is the
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* struct mt_list returned by MT_LIST_LOCK_ELT().
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*/
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#define MT_LIST_UNLOCK_ELT(el, np) \
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do { \
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struct mt_list *n = (np).next, *p = (np).prev; \
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(el)->next = n; \
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(el)->prev = p; \
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if (n != (el)) \
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n->prev = (el); \
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if (p != (el)) \
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p->next = (el); \
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} while (0)
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/* Internal macroes for the foreach macroes */
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#define _MT_LIST_UNLOCK_NEXT(el, np) \
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do { \
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struct mt_list *n = (np); \
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(el)->next = n; \
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if (n != (el)) \
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n->prev = (el); \
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} while (0)
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/* Internal macroes for the foreach macroes */
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#define _MT_LIST_UNLOCK_PREV(el, np) \
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do { \
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struct mt_list *p = (np); \
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(el)->prev = p; \
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if (p != (el)) \
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p->next = (el); \
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} while (0)
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#define _MT_LIST_LOCK_NEXT(el) \
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({ \
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struct mt_list *n = NULL; \
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while (1) { \
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struct mt_list *n2; \
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n = _HA_ATOMIC_XCHG(&((el)->next), MT_LIST_BUSY); \
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if (n == MT_LIST_BUSY) \
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continue; \
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if (n != (el)) { \
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n2 = _HA_ATOMIC_XCHG(&n->prev, MT_LIST_BUSY);\
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if (n2 == MT_LIST_BUSY) { \
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(el)->next = n; \
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__ha_barrier_store(); \
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continue; \
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} \
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} \
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break; \
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} \
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n; \
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})
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#define _MT_LIST_LOCK_PREV(el) \
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({ \
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struct mt_list *p = NULL; \
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while (1) { \
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struct mt_list *p2; \
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p = _HA_ATOMIC_XCHG(&((el)->prev), MT_LIST_BUSY); \
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if (p == MT_LIST_BUSY) \
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continue; \
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if (p != (el)) { \
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p2 = _HA_ATOMIC_XCHG(&p->next, MT_LIST_BUSY);\
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if (p2 == MT_LIST_BUSY) { \
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(el)->prev = p; \
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__ha_barrier_store(); \
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continue; \
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} \
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} \
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break; \
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} \
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p; \
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})
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#define _MT_LIST_RELINK_DELETED(elt2) \
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do { \
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struct mt_list *n = elt2.next, *p = elt2.prev; \
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n->prev = p; \
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p->next = n; \
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} while (0);
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/* Equivalent of MT_LIST_DEL(), to be used when parsing the list with mt_list_entry_for_each_safe().
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* It should be the element currently parsed (tmpelt1)
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*/
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#define MT_LIST_DEL_SAFE(el) \
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do { \
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(el)->prev = (el); \
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(el)->next = (el); \
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(el) = NULL; \
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} while (0)
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/* Simpler FOREACH_ITEM_SAFE macro inspired from Linux sources.
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* Iterates <item> through a list of items of type "typeof(*item)" which are
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* linked via a "struct list" member named <member>. A pointer to the head of
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* the list is passed in <list_head>. A temporary variable <back> of same type
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* as <item> is needed so that <item> may safely be deleted if needed.
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* tmpelt1 is a temporary struct mt_list *, and tmpelt2 is a temporary
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* struct mt_list, used internally, both are needed for MT_LIST_DEL_SAFE.
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* Example: list_for_each_entry_safe(cur_acl, tmp, known_acl, list, elt1, elt2)
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* { ... };
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* If you want to remove the current element, please use MT_LIST_DEL_SAFE.
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*/
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#define mt_list_for_each_entry_safe(item, list_head, member, tmpelt, tmpelt2) \
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for ((tmpelt) = NULL; (tmpelt) != MT_LIST_BUSY; ({ \
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if (tmpelt) { \
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if (tmpelt2.prev) \
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MT_LIST_UNLOCK_ELT(tmpelt, tmpelt2); \
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else \
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_MT_LIST_UNLOCK_NEXT(tmpelt, tmpelt2.next); \
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} else \
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_MT_LIST_RELINK_DELETED(tmpelt2); \
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(tmpelt) = MT_LIST_BUSY; \
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})) \
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for ((tmpelt) = (list_head), (tmpelt2).prev = NULL, (tmpelt2).next = _MT_LIST_LOCK_NEXT(list_head); ({ \
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(item) = MT_LIST_ELEM((tmpelt2.next), typeof(item), member); \
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if (&item->member != (list_head)) { \
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if (tmpelt2.prev != &item->member) \
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tmpelt2.next = _MT_LIST_LOCK_NEXT(&item->member); \
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else \
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tmpelt2.next = tmpelt; \
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if (tmpelt != NULL) { \
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if (tmpelt2.prev) \
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_MT_LIST_UNLOCK_PREV(tmpelt, tmpelt2.prev); \
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tmpelt2.prev = tmpelt; \
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} \
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(tmpelt) = &item->member; \
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} \
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}), \
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&item->member != (list_head);)
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#endif /* _COMMON_MINI_CLIST_H */
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