[patch] pi-futex: fix mm_struct memory leak

[Ingo Molnar <mingo@elte.hu>]

From: Vernon Mauery <vernux@us.ibm.com>
Subject: pi-futex: fix mm_struct memory leak

lock_queue was getting called essentially twice in a row and was
continually incrementing the mm_count ref count, thus causing a
memory leak.

Dinakar Guniguntala provided a proper fix for the problem that simply 
grabs the spinlock for the hash bucket queue rather than calling 
lock_queue.

The second time we do a queue_lock in futex_lock_pi, we really only need 
to take the hash bucket lock.

Signed-off-by: Dinakar Guniguntala <dino@in.ibm.com>
Signed-off-by: Vernon Mauery <vernux@us.ibm.com>
Acked-by: Paul E. McKenney <paulmck@us.ibm.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
---
 kernel/futex.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

Index: linux/kernel/futex.c
===================================================================
--- linux.orig/kernel/futex.c
+++ linux/kernel/futex.c
@@ -1208,7 +1208,7 @@ static int do_futex_lock_pi(u32 __user *
 	}
 
 	down_read(&curr->mm->mmap_sem);
-	hb = queue_lock(&q, -1, NULL);
+	spin_lock(q.lock_ptr);
 
 	/*
 	 * Got the lock. We might not be the anticipated owner if we