[tip:timers/core] hlist: Add hlist_is_singular_node() helper

[tip-bot for Thomas Gleixner]

Commit-ID:  15dba1e37b5cfd7fab9bc84e0f05f35c918f4eef
Gitweb:     http://git.kernel.org/tip/15dba1e37b5cfd7fab9bc84e0f05f35c918f4eef
Author:     Thomas Gleixner <tglx@xxxxxxxxxxxxx>
AuthorDate: Mon, 4 Jul 2016 09:50:27 +0000
Committer:  Ingo Molnar <mingo@xxxxxxxxxx>
CommitDate: Thu, 7 Jul 2016 10:35:07 +0200

hlist: Add hlist_is_singular_node() helper

Required to figure out whether the entry is the only one in the hlist.

Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Reviewed-by: Frederic Weisbecker <fweisbec@xxxxxxxxx>
Cc: Arjan van de Ven <arjan@xxxxxxxxxxxxx>
Cc: Chris Mason <clm@xxxxxx>
Cc: Eric Dumazet <edumazet@xxxxxxxxxx>
Cc: George Spelvin <linux@xxxxxxxxxxxxxxxxxxx>
Cc: Josh Triplett <josh@xxxxxxxxxxxxxxxx>
Cc: Len Brown <lenb@xxxxxxxxxx>
Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Cc: Paul E. McKenney <paulmck@xxxxxxxxxxxxxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: Rik van Riel <riel@xxxxxxxxxx>
Cc: rt@xxxxxxxxxxxxx
Link: http://lkml.kernel.org/r/20160704094341.867631372@xxxxxxxxxxxxx
Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx>
---
 include/linux/list.h | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/include/linux/list.h b/include/linux/list.h
index 5356f4d..5183138 100644
--- a/include/linux/list.h
+++ b/include/linux/list.h
@@ -679,6 +679,16 @@ static inline bool hlist_fake(struct hlist_node *h)
 }
 
 /*
+ * Check whether the node is the only node of the head without
+ * accessing head:
+ */
+static inline bool
+hlist_is_singular_node(struct hlist_node *n, struct hlist_head *h)
+{
+	return !n->next && n->pprev == &h->first;
+}
+
+/*
  * Move a list from one list head to another. Fixup the pprev
  * reference of the first entry if it exists.
  */