Merge master.kernel.org:/pub/scm/linux/kernel/git/roland/infiniband

[firefly-linux-kernel-4.4.55.git] / include / linux / list.h

diff --git a/include/linux/list.h b/include/linux/list.h
index 0f2435f92db333878f72fd70599905cc338d5d00..e6ec596822740ea70a2e6b4b865b704ba8bef4f7 100644 (file)
--- a/include/linux/list.h
+++ b/include/linux/list.h
@@ -634,6 +634,57 @@ static inline void hlist_add_after(struct hlist_node *n,
                next->next->pprev  = &next->next;
 }
 
+/**
+ * hlist_add_before_rcu - adds the specified element to the specified hlist
+ * before the specified node while permitting racing traversals.
+ * @n: the new element to add to the hash list.
+ * @next: the existing element to add the new element before.
+ *
+ * The caller must take whatever precautions are necessary
+ * (such as holding appropriate locks) to avoid racing
+ * with another list-mutation primitive, such as hlist_add_head_rcu()
+ * or hlist_del_rcu(), running on this same list.
+ * However, it is perfectly legal to run concurrently with
+ * the _rcu list-traversal primitives, such as
+ * hlist_for_each_rcu(), used to prevent memory-consistency
+ * problems on Alpha CPUs.
+ */
+static inline void hlist_add_before_rcu(struct hlist_node *n,
+                                       struct hlist_node *next)
+{
+       n->pprev = next->pprev;
+       n->next = next;
+       smp_wmb();
+       next->pprev = &n->next;
+       *(n->pprev) = n;
+}
+
+/**
+ * hlist_add_after_rcu - adds the specified element to the specified hlist
+ * after the specified node while permitting racing traversals.
+ * @prev: the existing element to add the new element after.
+ * @n: the new element to add to 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_add_head_rcu()
+ * or hlist_del_rcu(), running on this same list.
+ * However, it is perfectly legal to run concurrently with
+ * the _rcu list-traversal primitives, such as
+ * hlist_for_each_rcu(), used to prevent memory-consistency
+ * problems on Alpha CPUs.
+ */
+static inline void hlist_add_after_rcu(struct hlist_node *prev,
+                                      struct hlist_node *n)
+{
+       n->next = prev->next;
+       n->pprev = &prev->next;
+       smp_wmb();
+       prev->next = n;
+       if (n->next)
+               n->next->pprev = &n->next;
+}
+
 #define hlist_entry(ptr, type, member) container_of(ptr,type,member)
 
 #define hlist_for_each(pos, head) \