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smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=XcUCOqiJ; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="XcUCOqiJ" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 336FAC4CEE7; Fri, 1 Aug 2025 10:05:23 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1754042725; bh=w6pDTD1NLo2TxxU9cYo4iXHA37Y0HGWEzLWLKMXP5JQ=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=XcUCOqiJXtno7wspxwIoeunM3oJuz+wxoThzYMMvha3X3QyANwsjqHRTaLO8ncHj/ Ai/BVotdsfYyzVYU/cNUqY+z2SU3+5sRt0BrSWbj8NGOnaCsKxbR7K3vMtGvZNx5+L fihTM4zX+rKtIESGqBd4BZcofuOzf7rBhnq7n4aJbrlajufy9Z/xlh27sk11yLFpRe H7vZJrMviMLC3uGNpnF+OkWcx6p208I6AK4W4D4EwyWIBIrTXso/eR+pwtD/UILe6Y hDrWhwJhkbC6qFbPegwuKg5Kl+VAgosvRtgxOGZCiw3jteQxmLXhiK2/dFa4Kmtd6I 9JUZOoWeFSg0w== Date: Fri, 1 Aug 2025 11:05:20 +0100 From: Simon Horman To: Jijie Shao Cc: davem@davemloft.net, edumazet@google.com, kuba@kernel.org, pabeni@redhat.com, andrew+netdev@lunn.ch, shenjian15@huawei.com, liuyonglong@huawei.com, chenhao418@huawei.com, jonathan.cameron@huawei.com, shameerali.kolothum.thodi@huawei.com, salil.mehta@huawei.com, netdev@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH net 1/3] net: hibmcge: fix rtnl deadlock issue Message-ID: <20250801100520.GJ8494@horms.kernel.org> References: <20250731134749.4090041-1-shaojijie@huawei.com> <20250731134749.4090041-2-shaojijie@huawei.com> Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20250731134749.4090041-2-shaojijie@huawei.com> On Thu, Jul 31, 2025 at 09:47:47PM +0800, Jijie Shao wrote: > Currently, the hibmcge netdev acquires the rtnl_lock in > pci_error_handlers.reset_prepare() and releases it in > pci_error_handlers.reset_done(). > > However, in the PCI framework: > pci_reset_bus - __pci_reset_slot - pci_slot_save_and_disable_locked - > pci_dev_save_and_disable - err_handler->reset_prepare(dev); > > In pci_slot_save_and_disable_locked(): > list_for_each_entry(dev, &slot->bus->devices, bus_list) { > if (!dev->slot || dev->slot!= slot) > continue; > pci_dev_save_and_disable(dev); > if (dev->subordinate) > pci_bus_save_and_disable_locked(dev->subordinate); > } > > This will iterate through all devices under the current bus and execute > err_handler->reset_prepare(), causing two devices of the hibmcge driver > to sequentially request the rtnl_lock, leading to a deadlock. > > Since the driver now executes netif_device_detach() > before the reset process, it will not concurrently with > other netdev APIs, so there is no need to hold the rtnl_lock now. > > Therefore, this patch removes the rtnl_lock during the reset process and > adjusts the position of HBG_NIC_STATE_RESETTING to ensure > that multiple resets are not executed concurrently. > > Fixes: 3f5a61f6d504f ("net: hibmcge: Add reset supported in this module") > Signed-off-by: Jijie Shao > --- > drivers/net/ethernet/hisilicon/hibmcge/hbg_err.c | 13 ++++--------- > 1 file changed, 4 insertions(+), 9 deletions(-) > > diff --git a/drivers/net/ethernet/hisilicon/hibmcge/hbg_err.c b/drivers/net/ethernet/hisilicon/hibmcge/hbg_err.c > index 503cfbfb4a8a..94bc6f0da912 100644 > --- a/drivers/net/ethernet/hisilicon/hibmcge/hbg_err.c > +++ b/drivers/net/ethernet/hisilicon/hibmcge/hbg_err.c > @@ -53,9 +53,11 @@ static int hbg_reset_prepare(struct hbg_priv *priv, enum hbg_reset_type type) > { > int ret; > > - ASSERT_RTNL(); > + if (test_and_set_bit(HBG_NIC_STATE_RESETTING, &priv->state)) > + return -EBUSY; > > if (netif_running(priv->netdev)) { > + clear_bit(HBG_NIC_STATE_RESETTING, &priv->state); > dev_warn(&priv->pdev->dev, > "failed to reset because port is up\n"); > return -EBUSY; > @@ -64,7 +66,6 @@ static int hbg_reset_prepare(struct hbg_priv *priv, enum hbg_reset_type type) > netif_device_detach(priv->netdev); > > priv->reset_type = type; > - set_bit(HBG_NIC_STATE_RESETTING, &priv->state); > clear_bit(HBG_NIC_STATE_RESET_FAIL, &priv->state); > ret = hbg_hw_event_notify(priv, HBG_HW_EVENT_RESET); > if (ret) { > @@ -84,10 +85,8 @@ static int hbg_reset_done(struct hbg_priv *priv, enum hbg_reset_type type) > type != priv->reset_type) > return 0; > > - ASSERT_RTNL(); > - > - clear_bit(HBG_NIC_STATE_RESETTING, &priv->state); > ret = hbg_rebuild(priv); > + clear_bit(HBG_NIC_STATE_RESETTING, &priv->state); Hi Jijie, If I understand things correctly, then with this patch the HBG_NIC_STATE_RESETTING bit is used to prevent concurrent execution. Noting that a reset may be triggered via eththool, where hbg_reset() is used as a callback, I am concerned about concurrency implications for lines below this one. > if (ret) { > priv->stats.reset_fail_cnt++; > set_bit(HBG_NIC_STATE_RESET_FAIL, &priv->state); > @@ -101,12 +100,10 @@ static int hbg_reset_done(struct hbg_priv *priv, enum hbg_reset_type type) > return ret; > } > > -/* must be protected by rtnl lock */ > int hbg_reset(struct hbg_priv *priv) > { > int ret; > > - ASSERT_RTNL(); > ret = hbg_reset_prepare(priv, HBG_RESET_TYPE_FUNCTION); > if (ret) > return ret; > @@ -171,7 +168,6 @@ static void hbg_pci_err_reset_prepare(struct pci_dev *pdev) > struct net_device *netdev = pci_get_drvdata(pdev); > struct hbg_priv *priv = netdev_priv(netdev); > > - rtnl_lock(); > hbg_reset_prepare(priv, HBG_RESET_TYPE_FLR); > } > > @@ -181,7 +177,6 @@ static void hbg_pci_err_reset_done(struct pci_dev *pdev) > struct hbg_priv *priv = netdev_priv(netdev); > > hbg_reset_done(priv, HBG_RESET_TYPE_FLR); > - rtnl_unlock(); > } > > static const struct pci_error_handlers hbg_pci_err_handler = { > -- > 2.33.0 >