}
/**
- * list_splice_init_rcu - splice an RCU-protected list into an existing list.
+ * __list_splice_init_rcu - join an RCU-protected list into an existing list.
* @list: the RCU-protected list to splice
- * @head: the place in the list to splice the first list into
+ * @prev: points to the last element of the existing list
+ * @next: points to the first element of the existing list
* @sync: function to sync: synchronize_rcu(), synchronize_sched(), ...
*
- * @head can be RCU-read traversed concurrently with this function.
+ * The list pointed to by @prev and @next can be RCU-read traversed
+ * concurrently with this function.
*
* Note that this function blocks.
*
- * Important note: the caller must take whatever action is necessary to
- * prevent any other updates to @head. In principle, it is possible
- * to modify the list as soon as sync() begins execution.
- * If this sort of thing becomes necessary, an alternative version
- * based on call_rcu() could be created. But only if -really-
- * needed -- there is no shortage of RCU API members.
+ * Important note: the caller must take whatever action is necessary to prevent
+ * any other updates to the existing list. In principle, it is possible to
+ * modify the list as soon as sync() begins execution. If this sort of thing
+ * becomes necessary, an alternative version based on call_rcu() could be
+ * created. But only if -really- needed -- there is no shortage of RCU API
+ * members.
*/
-static inline void list_splice_init_rcu(struct list_head *list,
- struct list_head *head,
- void (*sync)(void))
+static inline void __list_splice_init_rcu(struct list_head *list,
+ struct list_head *prev,
+ struct list_head *next,
+ void (*sync)(void))
{
struct list_head *first = list->next;
struct list_head *last = list->prev;
- struct list_head *at = head->next;
-
- if (list_empty(list))
- return;
/*
* "first" and "last" tracking list, so initialize it. RCU readers
* this function.
*/
- last->next = at;
- rcu_assign_pointer(list_next_rcu(head), first);
- first->prev = head;
- at->prev = last;
+ last->next = next;
+ rcu_assign_pointer(list_next_rcu(prev), first);
+ first->prev = prev;
+ next->prev = last;
+}
+
+/**
+ * list_splice_init_rcu - splice an RCU-protected list into an existing list,
+ * designed for stacks.
+ * @list: the RCU-protected list to splice
+ * @head: the place in the existing list to splice the first list into
+ * @sync: function to sync: synchronize_rcu(), synchronize_sched(), ...
+ */
+static inline void list_splice_init_rcu(struct list_head *list,
+ struct list_head *head,
+ void (*sync)(void))
+{
+ if (!list_empty(list))
+ __list_splice_init_rcu(list, head, head->next, sync);
+}
+
+/**
+ * list_splice_tail_init_rcu - splice an RCU-protected list into an existing
+ * list, designed for queues.
+ * @list: the RCU-protected list to splice
+ * @head: the place in the existing list to splice the first list into
+ * @sync: function to sync: synchronize_rcu(), synchronize_sched(), ...
+ */
+static inline void list_splice_tail_init_rcu(struct list_head *list,
+ struct list_head *head,
+ void (*sync)(void))
+{
+ if (!list_empty(list))
+ __list_splice_init_rcu(list, head->prev, head, sync);
}
/**
likely(__ptr != __next) ? list_entry_rcu(__next, type, member) : NULL; \
})
+/**
+ * list_next_or_null_rcu - get the first element from a list
+ * @head: the head for the list.
+ * @ptr: the list head to take the next element from.
+ * @type: the type of the struct this is embedded in.
+ * @member: the name of the list_head within the struct.
+ *
+ * Note that if the ptr is at the end of the list, NULL is returned.
+ *
+ * This primitive may safely run concurrently with the _rcu list-mutation
+ * primitives such as list_add_rcu() as long as it's guarded by rcu_read_lock().
+ */
+#define list_next_or_null_rcu(head, ptr, type, member) \
+({ \
+ struct list_head *__head = (head); \
+ struct list_head *__ptr = (ptr); \
+ struct list_head *__next = READ_ONCE(__ptr->next); \
+ likely(__next != __head) ? list_entry_rcu(__next, type, \
+ member) : NULL; \
+})
+
/**
* list_for_each_entry_rcu - iterate over rcu list of given type
* @pos: the type * to use as a loop cursor.
&pos->member != (head); \
pos = list_entry_rcu(pos->member.next, typeof(*pos), member))
+/**
+ * list_entry_lockless - get the struct for this entry
+ * @ptr: the &struct list_head pointer.
+ * @type: the type of the struct this is embedded in.
+ * @member: the name of the list_head within the struct.
+ *
+ * This primitive may safely run concurrently with the _rcu list-mutation
+ * primitives such as list_add_rcu(), but requires some implicit RCU
+ * read-side guarding. One example is running within a special
+ * exception-time environment where preemption is disabled and where
+ * lockdep cannot be invoked (in which case updaters must use RCU-sched,
+ * as in synchronize_sched(), call_rcu_sched(), and friends). Another
+ * example is when items are added to the list, but never deleted.
+ */
+#define list_entry_lockless(ptr, type, member) \
+ container_of((typeof(ptr))lockless_dereference(ptr), type, member)
+
+/**
+ * list_for_each_entry_lockless - iterate over rcu list of given type
+ * @pos: the type * to use as a loop cursor.
+ * @head: the head for your list.
+ * @member: the name of the list_struct within the struct.
+ *
+ * This primitive may safely run concurrently with the _rcu list-mutation
+ * primitives such as list_add_rcu(), but requires some implicit RCU
+ * read-side guarding. One example is running within a special
+ * exception-time environment where preemption is disabled and where
+ * lockdep cannot be invoked (in which case updaters must use RCU-sched,
+ * as in synchronize_sched(), call_rcu_sched(), and friends). Another
+ * example is when items are added to the list, but never deleted.
+ */
+#define list_for_each_entry_lockless(pos, head, member) \
+ for (pos = list_entry_lockless((head)->next, typeof(*pos), member); \
+ &pos->member != (head); \
+ pos = list_entry_lockless(pos->member.next, typeof(*pos), member))
+
/**
* list_for_each_entry_continue_rcu - continue iteration over list of given type
* @pos: the type * to use as a loop cursor.
projects / cascardo / linux.git / blobdiff