[PATCH 1/3] Add hlist_for_each_entry_from_rcu

[Corey Minyard]

Add an RCU version of hlist_for_each_entry_from, getting ready for
converting the UDP hash lock to RCU.

Signed-off-by: Corey Minyard <cminyard@xxxxxxxxxx>
---
 include/linux/rculist.h |   18 ++++++++++++++++++
 1 files changed, 18 insertions(+), 0 deletions(-)

diff --git a/include/linux/rculist.h b/include/linux/rculist.h
index eb4443c..f20fe61 100644
--- a/include/linux/rculist.h
+++ b/include/linux/rculist.h
@@ -397,5 +397,23 @@ static inline void hlist_add_after_rcu(struct hlist_node *prev,
 		({ tpos = hlist_entry(pos, typeof(*tpos), member); 1; }); \
 		pos = rcu_dereference(pos->next))
 
+
+/**
+ * hlist_for_each_entry_from_rcu - iterate over rcu list starting from pos
+ * @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.
+ *
+ * This list-traversal primitive may safely run concurrently with
+ * the _rcu list-mutation primitives such as hlist_add_head_rcu()
+ * as long as the traversal is guarded by rcu_read_lock().
+ */
+#define hlist_for_each_entry_from_rcu(tpos, pos, member)                \
+	for (;                                                          \
+	     (pos) && ({ prefetch(pos->next); 1; }) &&    \
+	       ({ tpos = hlist_entry(pos, typeof(*tpos), member); 1; }); \
+	     pos = rcu_dereference(pos->next))
+
+
 #endif	/* __KERNEL__ */
 #endif
-- 
1.5.6.5

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