netdev - [PATCH net] net/mlx4: Fix irq-unsafe spinlock usage

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Date:   Wed, 23 May 2018 10:41:59 +0300
From:   Tariq Toukan <tariqt@...lanox.com>
To:     "David S. Miller" <davem@...emloft.net>
Cc:     netdev@...r.kernel.org, Eran Ben Elisha <eranbe@...lanox.com>,
        Jack Morgenstein <jackm@....mellanox.co.il>,
        Tariq Toukan <tariqt@...lanox.com>
Subject: [PATCH net] net/mlx4: Fix irq-unsafe spinlock usage

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

spin_lock/unlock was used instead of spin_un/lock_irq
in a procedure used in process space, on a spinlock
which can be grabbed in an interrupt.

This caused the stack trace below to be displayed (on kernel
4.17.0-rc1 compiled with Lock Debugging enabled):

[  154.661474] WARNING: SOFTIRQ-safe -> SOFTIRQ-unsafe lock order detected
[  154.668909] 4.17.0-rc1-rdma_rc_mlx+ #3 Tainted: G          I
[  154.675856] -----------------------------------------------------
[  154.682706] modprobe/10159 [HC0[0]:SC0[0]:HE0:SE1] is trying to acquire:
[  154.690254] 00000000f3b0e495 (&(&qp_table->lock)->rlock){+.+.}, at: mlx4_qp_remove+0x20/0x50 [mlx4_core]
[  154.700927]
and this task is already holding:
[  154.707461] 0000000094373b5d (&(&cq->lock)->rlock/1){....}, at: destroy_qp_common+0x111/0x560 [mlx4_ib]
[  154.718028] which would create a new lock dependency:
[  154.723705]  (&(&cq->lock)->rlock/1){....} -> (&(&qp_table->lock)->rlock){+.+.}
[  154.731922]
but this new dependency connects a SOFTIRQ-irq-safe lock:
[  154.740798]  (&(&cq->lock)->rlock){..-.}
[  154.740800]
... which became SOFTIRQ-irq-safe at:
[  154.752163]   _raw_spin_lock_irqsave+0x3e/0x50
[  154.757163]   mlx4_ib_poll_cq+0x36/0x900 [mlx4_ib]
[  154.762554]   ipoib_tx_poll+0x4a/0xf0 [ib_ipoib]
...
to a SOFTIRQ-irq-unsafe lock:
[  154.815603]  (&(&qp_table->lock)->rlock){+.+.}
[  154.815604]
... which became SOFTIRQ-irq-unsafe at:
[  154.827718] ...
[  154.827720]   _raw_spin_lock+0x35/0x50
[  154.833912]   mlx4_qp_lookup+0x1e/0x50 [mlx4_core]
[  154.839302]   mlx4_flow_attach+0x3f/0x3d0 [mlx4_core]

Since mlx4_qp_lookup() is called only in process space, we can
simply replace the spin_un/lock calls with spin_un/lock_irq calls.

Fixes: 6dc06c08bef1 ("net/mlx4: Fix the check in attaching steering rules")
Signed-off-by: Jack Morgenstein <jackm@....mellanox.co.il>
Signed-off-by: Tariq Toukan <tariqt@...lanox.com>
---

Hi Dave, please queue for -stable >= 4.12.

---
 drivers/net/ethernet/mellanox/mlx4/qp.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/net/ethernet/mellanox/mlx4/qp.c b/drivers/net/ethernet/mellanox/mlx4/qp.c
index 3aaf4bad6c5a..427e7a31862c 100644
--- a/drivers/net/ethernet/mellanox/mlx4/qp.c
+++ b/drivers/net/ethernet/mellanox/mlx4/qp.c
@@ -393,11 +393,11 @@ struct mlx4_qp *mlx4_qp_lookup(struct mlx4_dev *dev, u32 qpn)
 	struct mlx4_qp_table *qp_table = &mlx4_priv(dev)->qp_table;
 	struct mlx4_qp *qp;
 
-	spin_lock(&qp_table->lock);
+	spin_lock_irq(&qp_table->lock);
 
 	qp = __mlx4_qp_lookup(dev, qpn);
 
-	spin_unlock(&qp_table->lock);
+	spin_unlock_irq(&qp_table->lock);
 	return qp;
 }
 
-- 
1.8.3.1