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Mon, 26 Oct 2020 22:25:13 +0000 Date: Mon, 26 Oct 2020 19:25:12 -0300 From: Jason Gunthorpe To: Parav Pandit CC: , , , , , , Leon Romanovsky Subject: Re: [PATCH rdma-rc RESEND v1] RDMA/mlx5: Fix devlink deadlock on net namespace deletion Message-ID: <20201026222512.GB2066862@nvidia.com> References: <20201019052736.628909-1-leon@kernel.org> <20201026134359.23150-1-parav@nvidia.com> Content-Type: text/plain; charset="us-ascii" Content-Disposition: inline In-Reply-To: <20201026134359.23150-1-parav@nvidia.com> X-ClientProxiedBy: BL0PR0102CA0045.prod.exchangelabs.com (2603:10b6:208:25::22) To DM6PR12MB3834.namprd12.prod.outlook.com (2603:10b6:5:14a::12) MIME-Version: 1.0 X-MS-Exchange-MessageSentRepresentingType: 1 Received: from mlx.ziepe.ca (156.34.48.30) by BL0PR0102CA0045.prod.exchangelabs.com (2603:10b6:208:25::22) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.20.3499.18 via Frontend Transport; Mon, 26 Oct 2020 22:25:13 +0000 Received: from jgg by mlx with local (Exim 4.94) (envelope-from ) id 1kXAvQ-008fip-7w; Mon, 26 Oct 2020 19:25:12 -0300 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=nvidia.com; s=n1; t=1603751094; bh=GNl5jq9HUk30Ro5+CAAxiWjS05geCXV6Kqzf9VlXEHo=; h=ARC-Seal:ARC-Message-Signature:ARC-Authentication-Results:Date: From:To:CC:Subject:Message-ID:References:Content-Type: Content-Disposition:In-Reply-To:X-ClientProxiedBy:MIME-Version: X-MS-Exchange-MessageSentRepresentingType; b=TaKVNFfXjc8LCMiDRDJWlrKPJgamXEnZVX0AdLnkPyJtHNlnTinJs2i1WH5orQTR0 AIBrAGOXfp4aTbhPrZFCZTFy9qTifzmxxXawx383wA83K8G5ke/GgSsoPtwwrKUbZa ufq3Blt8hfSnzfKWEkAjJV5DqyY5hzMV+gLfWyFSDBdBYbU1cTGxLcH18mqdtkIB0n yQE+Jjnqll5sAOWBQUeo2kExeBzMYmbRuJekkyrSZM3WBrppN2vR/vA4K9WPsqHtkW sbTcFRpmDUZZLeIpyxMqZOYdeKwv8yvNXOulMXveeucTmQVLgKhp1F2B0qC0QtgBaL 9uW07KNVCjY9g== Precedence: bulk List-ID: X-Mailing-List: linux-rdma@vger.kernel.org On Mon, Oct 26, 2020 at 03:43:59PM +0200, Parav Pandit wrote: > When a mlx5 core devlink instance is reloaded in different net > namespace, its associated IB device is deleted and recreated. > > Example sequence is: > $ ip netns add foo > $ devlink dev reload pci/0000:00:08.0 netns foo > $ ip netns del foo > > mlx5 IB device needs to attach and detach the netdevice to it > through the netdev notifier chain during load and unload sequence. > A below call graph of the unload flow. > > cleanup_net() > down_read(&pernet_ops_rwsem); <- first sem acquired > ops_pre_exit_list() > pre_exit() > devlink_pernet_pre_exit() > devlink_reload() > mlx5_devlink_reload_down() > mlx5_unload_one() > [...] > mlx5_ib_remove() > mlx5_ib_unbind_slave_port() > mlx5_remove_netdev_notifier() > unregister_netdevice_notifier() > down_write(&pernet_ops_rwsem);<- recurrsive lock > > Hence, when net namespace is deleted, mlx5 reload results in deadlock. > > When deadlock occurs, devlink mutex is also held. This not only deadlocks > the mlx5 device under reload, but all the processes which attempt to access > unrelated devlink devices are deadlocked. > > Hence, fix this by mlx5 ib driver to register for per net netdev > notifier instead of global one, which operats on the net namespace > without holding the pernet_ops_rwsem. > > Fixes: 4383cfcc65e7 ("net/mlx5: Add devlink reload") > Signed-off-by: Parav Pandit > Signed-off-by: Leon Romanovsky > --- > Changelog: > v0->v1: > - updated comment for mlx5_core_net API to be used by multiple mlx5 > drivers > --- > drivers/infiniband/hw/mlx5/main.c | 6 ++++-- > .../net/ethernet/mellanox/mlx5/core/lib/mlx5.h | 5 ----- > include/linux/mlx5/driver.h | 18 ++++++++++++++++++ > 3 files changed, 22 insertions(+), 7 deletions(-) Applied to for-rc, thanks Jason