From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-16.7 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 1A854C432BE for ; Tue, 10 Aug 2021 07:08:10 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id F08AC61019 for ; Tue, 10 Aug 2021 07:08:09 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S237256AbhHJHI3 (ORCPT ); Tue, 10 Aug 2021 03:08:29 -0400 Received: from mail.kernel.org ([198.145.29.99]:46856 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231535AbhHJHI0 (ORCPT ); Tue, 10 Aug 2021 03:08:26 -0400 Received: by mail.kernel.org (Postfix) with ESMTPSA id 1524460EFF; Tue, 10 Aug 2021 07:08:03 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1628579284; bh=wdPjk4FkZsB5gtwP0grHrE2IXLuYuMTNiOrU9r96BPI=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=k2cimawheqFmESKO/fgNTCsmob9XOOQpSt21S4A1y6KooRLLhWwTpRTZs48fMegtk zVfwaClF3oDoPVnDR2US15hzx+e1c1Nfr0i/iUXSFtbf/4YPN4KelucA7bZZ+3HbMp 5+Poop6nML8fDzUOZ8Ml3HDnduItLnAQrTTUwf9jch79N6KSQYJNbv36q8i+O4urXz ogPg7jfAfOYmk83warVQ8ipa/9Muc8ulZPBf90UuEbqf40Atont4Bz4Y0wHGBARMPZ pKa7WnGyb7TAiHj8LqFcum2XLCjMomcN8ETnVl0vP2lISpGd4v0N5yLxFB6Qz33AD/ 98nNCXg/yZMSQ== Date: Tue, 10 Aug 2021 10:08:01 +0300 From: Leon Romanovsky To: AceLan Kao Cc: "David S. Miller" , Jakub Kicinski , Eric Dumazet , Daniel Borkmann , Antoine Tenart , Alexander Lobakin , Wei Wang , Taehee Yoo , =?iso-8859-1?Q?Bj=F6rn_T=F6pel?= , Heiner Kallweit , netdev@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [RESEND][PATCH] net: called rtnl_unlock() before runpm resumes devices Message-ID: References: <20210809032809.1224002-1-acelan.kao@canonical.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Aug 10, 2021 at 09:57:57AM +0800, AceLan Kao wrote: > Leon Romanovsky 於 2021年8月9日 週一 下午1:51寫道： > > > > On Mon, Aug 09, 2021 at 11:28:09AM +0800, 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(), > > > > Why? It doesn't sound right that drivers internally decide if to take or > > release some external to them lock without seeing full picture. > From what I observed, this is the only calling path that acquired > rtnl_lock() before calling drivers' resume function. > So, it encounters recursive lock while driver is going to cal rtnl_lock() again. I clearly see the problem, but don't agree with a solution. > > > > > Most of the time, device driver authors do it wrong. I afraid that igs > > is one of such drivers that did it wrong. > The issues could be if we remove rtnl_lock in device drivers, then in > other calling path, it won't be protected by the rtnl lock, > and maybe we shouldn't call pm_runtime_resume() here(within rtnl > lock), for device drivers don't know if they are protected by the rtnl > lock while their resume() got called. This is exactly the problem, every driver guesses if rtnl_lock is needed or not in specific path. It is wrong by design. You should ensure that all paths that are triggered through rtnl should hold rtnl_lock. You dropped rtnl_lock() without any protection, it is 100% bug. Thanks > > > > > Thanks > > > > > so call rtnl_unlock() before calling pm_runtime_resume() and then call > > > rtnl_lock() after it in __dev_open(). > > > > > > [ 967.723577] INFO: task ip:6024 blocked for more than 120 seconds. > > > [ 967.723588] Not tainted 5.12.0-rc3+ #1 > > > [ 967.723592] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. > > > [ 967.723594] task:ip state:D stack: 0 pid: 6024 ppid: 5957 flags:0x00004000 > > > [ 967.723603] Call Trace: > > > [ 967.723610] __schedule+0x2de/0x890 > > > [ 967.723623] schedule+0x4f/0xc0 > > > [ 967.723629] schedule_preempt_disabled+0xe/0x10 > > > [ 967.723636] __mutex_lock.isra.0+0x190/0x510 > > > [ 967.723644] __mutex_lock_slowpath+0x13/0x20 > > > [ 967.723651] mutex_lock+0x32/0x40 > > > [ 967.723657] rtnl_lock+0x15/0x20 > > > [ 967.723665] igb_resume+0xee/0x1d0 [igb] > > > [ 967.723687] ? pci_pm_default_resume+0x30/0x30 > > > [ 967.723696] igb_runtime_resume+0xe/0x10 [igb] > > > [ 967.723713] pci_pm_runtime_resume+0x74/0x90 > > > [ 967.723718] __rpm_callback+0x53/0x1c0 > > > [ 967.723725] rpm_callback+0x57/0x80 > > > [ 967.723730] ? pci_pm_default_resume+0x30/0x30 > > > [ 967.723735] rpm_resume+0x547/0x760 > > > [ 967.723740] __pm_runtime_resume+0x52/0x80 > > > [ 967.723745] __dev_open+0x56/0x160 > > > [ 967.723753] ? _raw_spin_unlock_bh+0x1e/0x20 > > > [ 967.723758] __dev_change_flags+0x188/0x1e0 > > > [ 967.723766] dev_change_flags+0x26/0x60 > > > [ 967.723773] do_setlink+0x723/0x10b0 > > > [ 967.723782] ? __nla_validate_parse+0x5b/0xb80 > > > [ 967.723792] __rtnl_newlink+0x594/0xa00 > > > [ 967.723800] ? nla_put_ifalias+0x38/0xa0 > > > [ 967.723807] ? __nla_reserve+0x41/0x50 > > > [ 967.723813] ? __nla_reserve+0x41/0x50 > > > [ 967.723818] ? __kmalloc_node_track_caller+0x49b/0x4d0 > > > [ 967.723824] ? pskb_expand_head+0x75/0x310 > > > [ 967.723830] ? nla_reserve+0x28/0x30 > > > [ 967.723835] ? skb_free_head+0x25/0x30 > > > [ 967.723843] ? security_sock_rcv_skb+0x2f/0x50 > > > [ 967.723850] ? netlink_deliver_tap+0x3d/0x210 > > > [ 967.723859] ? sk_filter_trim_cap+0xc1/0x230 > > > [ 967.723863] ? skb_queue_tail+0x43/0x50 > > > [ 967.723870] ? sock_def_readable+0x4b/0x80 > > > [ 967.723876] ? __netlink_sendskb+0x42/0x50 > > > [ 967.723888] ? security_capable+0x3d/0x60 > > > [ 967.723894] ? __cond_resched+0x19/0x30 > > > [ 967.723900] ? kmem_cache_alloc_trace+0x390/0x440 > > > [ 967.723906] rtnl_newlink+0x49/0x70 > > > [ 967.723913] rtnetlink_rcv_msg+0x13c/0x370 > > > [ 967.723920] ? _copy_to_iter+0xa0/0x460 > > > [ 967.723927] ? rtnl_calcit.isra.0+0x130/0x130 > > > [ 967.723934] netlink_rcv_skb+0x55/0x100 > > > [ 967.723939] rtnetlink_rcv+0x15/0x20 > > > [ 967.723944] netlink_unicast+0x1a8/0x250 > > > [ 967.723949] netlink_sendmsg+0x233/0x460 > > > [ 967.723954] sock_sendmsg+0x65/0x70 > > > [ 967.723958] ____sys_sendmsg+0x218/0x290 > > > [ 967.723961] ? copy_msghdr_from_user+0x5c/0x90 > > > [ 967.723966] ? lru_cache_add_inactive_or_unevictable+0x27/0xb0 > > > [ 967.723974] ___sys_sendmsg+0x81/0xc0 > > > [ 967.723980] ? __mod_memcg_lruvec_state+0x22/0xe0 > > > [ 967.723987] ? kmem_cache_free+0x244/0x420 > > > [ 967.723991] ? dentry_free+0x37/0x70 > > > [ 967.723996] ? mntput_no_expire+0x4c/0x260 > > > [ 967.724001] ? __cond_resched+0x19/0x30 > > > [ 967.724007] ? security_file_free+0x54/0x60 > > > [ 967.724013] ? call_rcu+0xa4/0x250 > > > [ 967.724021] __sys_sendmsg+0x62/0xb0 > > > [ 967.724026] ? exit_to_user_mode_prepare+0x3d/0x1a0 > > > [ 967.724032] __x64_sys_sendmsg+0x1f/0x30 > > > [ 967.724037] do_syscall_64+0x38/0x90 > > > [ 967.724044] entry_SYSCALL_64_after_hwframe+0x44/0xae > > > > > > Fixes: bd869245a3dc ("net: core: try to runtime-resume detached device in __dev_open") > > > Signed-off-by: Chia-Lin Kao (AceLan) > > > --- > > > net/core/dev.c | 5 ++++- > > > 1 file changed, 4 insertions(+), 1 deletion(-) > > > > > > diff --git a/net/core/dev.c b/net/core/dev.c > > > index 8f1a47ad6781..dd43a29419fd 100644 > > > --- a/net/core/dev.c > > > +++ b/net/core/dev.c > > > @@ -1585,8 +1585,11 @@ static int __dev_open(struct net_device *dev, struct netlink_ext_ack *extack) > > > > > > if (!netif_device_present(dev)) { > > > /* may be detached because parent is runtime-suspended */ > > > - if (dev->dev.parent) > > > + if (dev->dev.parent) { > > > + rtnl_unlock(); > > > pm_runtime_resume(dev->dev.parent); > > > + rtnl_lock(); > > > + } > > > if (!netif_device_present(dev)) > > > return -ENODEV; > > > } > > > -- > > > 2.25.1 > > >