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(p200300ea8f3846000d4b063c654f4f21.dip0.t-ipconnect.de. [2003:ea:8f38:4600:d4b:63c:654f:4f21]) by smtp.googlemail.com with ESMTPSA id g9sm11469796wmh.21.2021.04.24.13.07.57 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Sat, 24 Apr 2021 13:07:58 -0700 (PDT) To: AceLan Kao Cc: Jakub Kicinski , Eric Dumazet , "David S. Miller" , Alexei Starovoitov , Andrii Nakryiko , Wei Wang , Cong Wang , Taehee Yoo , =?UTF-8?B?QmrDtnJuIFTDtnBlbA==?= , netdev , LKML References: <20210420075406.64105-1-acelan.kao@canonical.com> <20210420122715.2066b537@kicinski-fedora-pc1c0hjn.dhcp.thefacebook.com> From: Heiner Kallweit Subject: Re: [PATCH] net: called rtnl_unlock() before runpm resumes devices Message-ID: Date: Sat, 24 Apr 2021 22:07:50 +0200 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:78.0) Gecko/20100101 Thunderbird/78.10.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 23.04.2021 05:42, AceLan Kao wrote: > Heiner Kallweit 於 2021年4月22日 週四 下午3:09寫道： >> >> On 22.04.2021 08:30, AceLan Kao wrote: >>> Yes, should add >>> >>> Fixes: 9474933caf21 ("igb: close/suspend race in netif_device_detach") >>> and also >>> Fixes: 9513d2a5dc7f ("igc: Add legacy power management support") >>> >> Please don't top-post. Apart from that: >> If the issue was introduced with driver changes, then adding a workaround >> in net core may not be the right approach. > It's hard to say who introduces this issue, we probably could point > our finger to below commit > bd869245a3dc net: core: try to runtime-resume detached device in __dev_open > > This calling path is not usual, in my case, the NIC is not plugged in > any Ethernet cable, > and we are doing networking tests on another NIC on the system. So, > remove the rtnl lock from igb driver will affect other scenarios. > >> >>> Jakub Kicinski 於 2021年4月21日 週三 上午3:27寫道： >>>> >>>> On Tue, 20 Apr 2021 10:34:17 +0200 Eric Dumazet wrote: >>>>> On Tue, Apr 20, 2021 at 9:54 AM AceLan Kao wrote: >>>>>> >>>>>> From: "Chia-Lin Kao (AceLan)" >>>>>> >>>>>> The rtnl_lock() has been called in rtnetlink_rcv_msg(), and then in >>>>>> __dev_open() it calls pm_runtime_resume() to resume devices, and in >>>>>> some devices' resume function(igb_resum,igc_resume) they calls rtnl_lock() >>>>>> again. That leads to a recursive lock. >>>>>> >>>>>> It should leave the devices' resume function to decide if they need to >>>>>> call rtnl_lock()/rtnl_unlock(), so call rtnl_unlock() before calling >>>>>> pm_runtime_resume() and then call rtnl_lock() after it in __dev_open(). >>>>>> >>>>>> >>>>> >>>>> Hi Acelan >>>>> >>>>> When was the bugg added ? >>>>> Please add a Fixes: tag >>>> >>>> For immediate cause probably: >>>> >>>> Fixes: 9474933caf21 ("igb: close/suspend race in netif_device_detach") >>>> >>>>> By doing so, you give more chances for reviewers to understand why the >>>>> fix is not risky, >>>>> and help stable teams work. >>>> >>>> IMO the driver lacks internal locking. Taking 看rtnl from resume is just >>>> one example, git history shows many more places that lacked locking and >>>> got papered over with rtnl here. >> You could alternatively try the following. It should avoid the deadlock, and when runtime-resuming if __IGB_DOWN is set all we do is marking the net_device as present (because of PCI D3 -> D0 transition). I do basically the same in r8169 and it works as intended. Disclaimer: I don't have an igb-driven device and therefore can't test the proposal. diff --git a/drivers/net/ethernet/intel/igb/igb_main.c b/drivers/net/ethernet/intel/igb/igb_main.c index 038a9fd1a..21436626a 100644 --- a/drivers/net/ethernet/intel/igb/igb_main.c +++ b/drivers/net/ethernet/intel/igb/igb_main.c @@ -9300,6 +9300,14 @@ static int __maybe_unused igb_runtime_suspend(struct device *dev) static int __maybe_unused igb_runtime_resume(struct device *dev) { + struct net_device *netdev = dev_get_drvdata(dev); + struct igb_adapter *adapter = netdev_priv(netdev); + + if (test_bit(__IGB_DOWN, &adapter->state)) { + netif_device_attach(netdev); + return 0; + } + return igb_resume(dev); } -- 2.31.1