linux-kernel - [ 043/221] IB/mlx4: Fix spinlock order to avoid lockdep warnings

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Date:	Tue, 15 Jan 2013 10:49:30 -0800
From:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:	linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	alan@...rguk.ukuu.org.uk,
	Jack Morgenstein <jackm@....mellanox.co.il>,
	Or Gerlitz <ogerlitz@...lanox.com>,
	Roland Dreier <roland@...estorage.com>
Subject: [ 043/221] IB/mlx4: Fix spinlock order to avoid lockdep warnings

3.7-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Jack Morgenstein <jackm@....mellanox.co.il>

commit ceb7decb366591e9b67d70832e07f5d240572a3d upstream.

lockdep warns about taking a hard-irq-unsafe lock (sriov->id_map_lock)
inside a hard-irq-safe lock (sriov->going_down_lock).

Since id_map_lock is never taken in the interrupt context, we can
simply reverse the order of taking the two spinlocks, thus avoiding
the warning and the depencency.

Signed-off-by: Jack Morgenstein <jackm@....mellanox.co.il>
Signed-off-by: Or Gerlitz <ogerlitz@...lanox.com>
Signed-off-by: Roland Dreier <roland@...estorage.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 drivers/infiniband/hw/mlx4/cm.c |    4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

--- a/drivers/infiniband/hw/mlx4/cm.c
+++ b/drivers/infiniband/hw/mlx4/cm.c
@@ -268,15 +268,15 @@ static void schedule_delayed(struct ib_d
 	struct mlx4_ib_sriov *sriov = &to_mdev(ibdev)->sriov;
 	unsigned long flags;
 
-	spin_lock_irqsave(&sriov->going_down_lock, flags);
 	spin_lock(&sriov->id_map_lock);
+	spin_lock_irqsave(&sriov->going_down_lock, flags);
 	/*make sure that there is no schedule inside the scheduled work.*/
 	if (!sriov->is_going_down) {
 		id->scheduled_delete = 1;
 		schedule_delayed_work(&id->timeout, CM_CLEANUP_CACHE_TIMEOUT);
 	}
-	spin_unlock(&sriov->id_map_lock);
 	spin_unlock_irqrestore(&sriov->going_down_lock, flags);
+	spin_unlock(&sriov->id_map_lock);
 }
 
 int mlx4_ib_multiplex_cm_handler(struct ib_device *ibdev, int port, int slave_id,


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