linux-kernel - [PATCH 3/3] llist: llist_add() can use llist_add

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Message-ID: <20130615173046.GA15068@redhat.com>
Date:	Sat, 15 Jun 2013 19:30:46 +0200
From:	Oleg Nesterov <oleg@...hat.com>
To:	Andrew Morton <akpm@...ux-foundation.org>
Cc:	Al Viro <viro@...iv.linux.org.uk>,
	Andrey Vagin <avagin@...nvz.org>,
	"Eric W. Biederman" <ebiederm@...ssion.com>,
	David Howells <dhowells@...hat.com>,
	Huang Ying <ying.huang@...el.com>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	linux-kernel@...r.kernel.org
Subject: [PATCH 3/3] llist: llist_add() can use llist_add_batch()

llist_add(new, head) can simply use llist_add_batch(new, new, head),
no need to duplicate the code.

This obviously uninlines llist_add() and to me this is a win. But we
can make llist_add_batch() inline if this is desirable, in this case
gcc can notice that new_first == new_last if the caller is llist_add().

Signed-off-by: Oleg Nesterov <oleg@...hat.com>
---
 include/linux/llist.h |   14 ++++----------
 1 files changed, 4 insertions(+), 10 deletions(-)

diff --git a/include/linux/llist.h b/include/linux/llist.h
index 3e2b969..cdaa7f0 100644
--- a/include/linux/llist.h
+++ b/include/linux/llist.h
@@ -142,6 +142,9 @@ static inline struct llist_node *llist_next(struct llist_node *node)
 	return node->next;
 }
 
+extern bool llist_add_batch(struct llist_node *new_first,
+			    struct llist_node *new_last,
+			    struct llist_head *head);
 /**
  * llist_add - add a new entry
  * @new:	new entry to be added
@@ -151,13 +154,7 @@ static inline struct llist_node *llist_next(struct llist_node *node)
  */
 static inline bool llist_add(struct llist_node *new, struct llist_head *head)
 {
-	struct llist_node *first;
-
-	do {
-		new->next = first = ACCESS_ONCE(head->first);
-	} while (cmpxchg(&head->first, first, new) != first);
-
-	return !first;
+	return llist_add_batch(new, new, head);
 }
 
 /**
@@ -173,9 +170,6 @@ static inline struct llist_node *llist_del_all(struct llist_head *head)
 	return xchg(&head->first, NULL);
 }
 
-extern bool llist_add_batch(struct llist_node *new_first,
-			    struct llist_node *new_last,
-			    struct llist_head *head);
 extern struct llist_node *llist_del_first(struct llist_head *head);
 
 #endif /* LLIST_H */
-- 
1.5.5.1

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