From e89b6d5bae3c74aa4abb3c0a74d2fe6bbb822b41 Mon Sep 17 00:00:00 2001
From: Ingo Molnar <mingo@elte.hu>
Date: Mon, 3 Jul 2006 00:25:05 -0700
Subject: [PATCH] --- yaml --- r: 31815 b: refs/heads/master c:
 8b8f319fc7f4ab59f567d6a401a62659b3d37007 h: refs/heads/master i:   31813:
 5d53cc023036178996a9cf2965103a6e20ca02ec   31811:
 ac748fcfa555573aea1ad3a3ae8679e32b00667b   31807:
 751c8fe3e201192bd7ade00fba0d6d8be5394a8d v: v3

---
 [refs]               |  2 +-
 trunk/kernel/futex.c | 28 ++++++++++++++++++----------
 2 files changed, 19 insertions(+), 11 deletions(-)

diff --git a/[refs] b/[refs]
index a9e461266691..12c4ad84f230 100644
--- a/[refs]
+++ b/[refs]
@@ -1,2 +1,2 @@
 ---
-refs/heads/master: f2eace23e924bd3f05aedea4fc505eb5508d2d93
+refs/heads/master: 8b8f319fc7f4ab59f567d6a401a62659b3d37007
diff --git a/trunk/kernel/futex.c b/trunk/kernel/futex.c
index 15caf93e4a43..1dc98e4dd287 100644
--- a/trunk/kernel/futex.c
+++ b/trunk/kernel/futex.c
@@ -606,6 +606,22 @@ static int unlock_futex_pi(u32 __user *uaddr, u32 uval)
 	return 0;
 }
 
+/*
+ * Express the locking dependencies for lockdep:
+ */
+static inline void
+double_lock_hb(struct futex_hash_bucket *hb1, struct futex_hash_bucket *hb2)
+{
+	if (hb1 <= hb2) {
+		spin_lock(&hb1->lock);
+		if (hb1 < hb2)
+			spin_lock_nested(&hb2->lock, SINGLE_DEPTH_NESTING);
+	} else { /* hb1 > hb2 */
+		spin_lock(&hb2->lock);
+		spin_lock_nested(&hb1->lock, SINGLE_DEPTH_NESTING);
+	}
+}
+
 /*
  * Wake up all waiters hashed on the physical page that is mapped
  * to this virtual address:
@@ -674,11 +690,7 @@ futex_wake_op(u32 __user *uaddr1, u32 __user *uaddr2,
 	hb2 = hash_futex(&key2);
 
 retry:
-	if (hb1 < hb2)
-		spin_lock(&hb1->lock);
-	spin_lock(&hb2->lock);
-	if (hb1 > hb2)
-		spin_lock(&hb1->lock);
+	double_lock_hb(hb1, hb2);
 
 	op_ret = futex_atomic_op_inuser(op, uaddr2);
 	if (unlikely(op_ret < 0)) {
@@ -787,11 +799,7 @@ static int futex_requeue(u32 __user *uaddr1, u32 __user *uaddr2,
 	hb1 = hash_futex(&key1);
 	hb2 = hash_futex(&key2);
 
-	if (hb1 < hb2)
-		spin_lock(&hb1->lock);
-	spin_lock(&hb2->lock);
-	if (hb1 > hb2)
-		spin_lock(&hb1->lock);
+	double_lock_hb(hb1, hb2);
 
 	if (likely(cmpval != NULL)) {
 		u32 curval;