[PATCH] lockdep: annotate futex

Teach special (recursive) locking code to the lock validator.  Introduces
double_lock_hb() to unify double- hash-bucket-lock taking.

Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Arjan van de Ven <arjan@linux.intel.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

1 files changed, 18 insertions, 10 deletions

diff --git a/kernel/futex.c b/kernel/futex.c
index 15caf93e4a43..1dc98e4dd287 100644
--- a/kernel/futex.c
+++ b/kernel/futex.c
@@ -607,6 +607,22 @@ static int unlock_futex_pi(u32 __user *uaddr, u32 uval)
 }
 
 /*
+ * 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 @@ retryfull:
         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;