Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67;
From:   Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To:     linux-kernel@vger.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        stable@vger.kernel.org, Moshe Shemesh <moshe@mellanox.com>,
        Saeed Mahameed <saeedm@mellanox.com>,
        Sasha Levin <sashal@kernel.org>
Subject: [PATCH 4.9 078/171] net/mlx5: Fix health work queue spin lock to IRQ safe
Date:   Thu,  8 Nov 2018 13:50:48 -0800
Message-Id: <20181108215133.199210073@linuxfoundation.org>
In-Reply-To: <20181108215127.257643509@linuxfoundation.org>
References: <20181108215127.257643509@linuxfoundation.org>
User-Agent: quilt/0.65
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

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

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

[ Upstream commit 6377ed0bbae6fa28853e1679d068a9106c8a8908 ]

spin_lock/unlock of health->wq_lock should be IRQ safe.
It was changed to spin_lock_irqsave since adding commit 0179720d6be2
("net/mlx5: Introduce trigger_health_work function") which uses
spin_lock from asynchronous event (IRQ) context.
Thus, all spin_lock/unlock of health->wq_lock should have been moved
to IRQ safe mode.
However, one occurrence on new code using this lock missed that
change, resulting in possible deadlock:
  kernel: Possible unsafe locking scenario:
  kernel:       CPU0
  kernel:       ----
  kernel:  lock(&(&health->wq_lock)->rlock);
  kernel:  <Interrupt>
  kernel:    lock(&(&health->wq_lock)->rlock);
  kernel: #012 *** DEADLOCK ***

Fixes: 2a0165a034ac ("net/mlx5: Cancel delayed recovery work when unloading the driver")
Signed-off-by: Moshe Shemesh <moshe@mellanox.com>
Signed-off-by: Saeed Mahameed <saeedm@mellanox.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 drivers/net/ethernet/mellanox/mlx5/core/health.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/drivers/net/ethernet/mellanox/mlx5/core/health.c b/drivers/net/ethernet/mellanox/mlx5/core/health.c
index 448e71e07668..264f51b3409d 100644
--- a/drivers/net/ethernet/mellanox/mlx5/core/health.c
+++ b/drivers/net/ethernet/mellanox/mlx5/core/health.c
@@ -369,10 +369,11 @@ void mlx5_drain_health_wq(struct mlx5_core_dev *dev)
 void mlx5_drain_health_recovery(struct mlx5_core_dev *dev)
 {
 	struct mlx5_core_health *health = &dev->priv.health;
+	unsigned long flags;
 
-	spin_lock(&health->wq_lock);
+	spin_lock_irqsave(&health->wq_lock, flags);
 	set_bit(MLX5_DROP_NEW_RECOVERY_WORK, &health->flags);
-	spin_unlock(&health->wq_lock);
+	spin_unlock_irqrestore(&health->wq_lock, flags);
 	cancel_delayed_work_sync(&dev->priv.health.recover_work);
 }
 
-- 
2.17.1