From 1746056588ce2c701fae30208669b00e55f0c0ed Mon Sep 17 00:00:00 2001
From: Corey Minyard <minyard@acm.org>
Date: Sat, 10 Feb 2007 01:45:42 -0800
Subject: [PATCH] --- yaml --- r: 47567 b: refs/heads/master c:
 3678d62f028689abc8ac5693b254e48f605f94ba h: refs/heads/master i:   47565:
 05cbc2e19fa5357bb5bef76bbf0368077061f2b3   47563:
 551e22f0c990995f2c2dfbc29eac149a06201b67   47559:
 2b3e95bd3a7f3da45e7527dd599cf374f66f17a2   47551:
 53949988fb2770e25d15e8962e5aa8709a3181e5 v: v3

---
 [refs]                     |  2 +-
 trunk/include/linux/list.h | 56 ++++++++++++++++++++++++++++++++++++++
 2 files changed, 57 insertions(+), 1 deletion(-)

diff --git a/[refs] b/[refs]
index 9f7af6092535..929fb838d70f 100644
--- a/[refs]
+++ b/[refs]
@@ -1,2 +1,2 @@
 ---
-refs/heads/master: 16cf5b39b81b95d1e3d81df3ba8c82cadf54f551
+refs/heads/master: 3678d62f028689abc8ac5693b254e48f605f94ba
diff --git a/trunk/include/linux/list.h b/trunk/include/linux/list.h
index 611059d633f4..cdc96559e5ae 100644
--- a/trunk/include/linux/list.h
+++ b/trunk/include/linux/list.h
@@ -359,6 +359,62 @@ static inline void list_splice_init(struct list_head *list,
 	}
 }
 
+/**
+ * list_splice_init_rcu - splice 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
+ * @sync:	function to sync: synchronize_rcu(), synchronize_sched(), ...
+ *
+ * @head 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.
+ */
+static inline void list_splice_init_rcu(struct list_head *list,
+					struct list_head *head,
+					void (*sync)(void))
+{
+	struct list_head *first = list->next;
+	struct list_head *last = list->prev;
+	struct list_head *at = head->next;
+
+	if (list_empty(head))
+		return;
+
+	/* "first" and "last" tracking list, so initialize it. */
+
+	INIT_LIST_HEAD(list);
+
+	/*
+	 * At this point, the list body still points to the source list.
+	 * Wait for any readers to finish using the list before splicing
+	 * the list body into the new list.  Any new readers will see
+	 * an empty list.
+	 */
+
+	sync();
+
+	/*
+	 * Readers are finished with the source list, so perform splice.
+	 * The order is important if the new list is global and accessible
+	 * to concurrent RCU readers.  Note that RCU readers are not
+	 * permitted to traverse the prev pointers without excluding
+	 * this function.
+	 */
+
+	last->next = at;
+	smp_wmb();
+	head->next = first;
+	first->prev = head;
+	at->prev = last;
+}
+
 /**
  * list_entry - get the struct for this entry
  * @ptr:	the &struct list_head pointer.