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[23.128.96.18]) by mx.google.com with ESMTP id l5si3860412jaj.63.2021.09.02.17.52.15; Thu, 02 Sep 2021 17:52:45 -0700 (PDT) Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) client-ip=23.128.96.18; Authentication-Results: mx.google.com; dkim=fail (test mode) header.i=@armlinux.org.uk header.s=pandora-2019 header.b=uqsMXDZa; spf=pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org; dmarc=fail (p=NONE sp=NONE dis=NONE) header.from=armlinux.org.uk Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S242547AbhIBUEI (ORCPT + 99 others); Thu, 2 Sep 2021 16:04:08 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:41736 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229758AbhIBUEH (ORCPT ); Thu, 2 Sep 2021 16:04:07 -0400 Received: from pandora.armlinux.org.uk (pandora.armlinux.org.uk [IPv6:2001:4d48:ad52:32c8:5054:ff:fe00:142]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id C866EC061575; Thu, 2 Sep 2021 13:03:08 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=armlinux.org.uk; s=pandora-2019; h=Sender:In-Reply-To: Content-Transfer-Encoding:Content-Type:MIME-Version:References:Message-ID: Subject:Cc:To:From:Date:Reply-To:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Id: List-Help:List-Unsubscribe:List-Subscribe:List-Post:List-Owner:List-Archive; bh=HjCPobaicATTQhQvs0MFgxl93rLs6U0O7or7Fen91wA=; b=uqsMXDZaQHY+hAnQkNxWRvQq3 K7o5qh8Z0AxzTtcdHTzhA7OgJdalCne+0doPhBBrOXfVIHhyNndMh82OQu8I1HdSW88a8V/Fw+XWz jIetSLLC3jC6v6QWY7v3J66ZVwq6p0WHxclG/I8+ifo+DTAMEnjUF1WESIAnAWc3PSbwEFmnlnWtL 5Mu1YLsrpKy/7URjauscklPrpEXQJbTGaqUu50da8d79zHO7yReGwthKMC5rPV+vFP714EF/W+BHZ klxn+wdE+UdRxD8JYYJC2sKHrJZoGlklxmEzJGT4OqvArrPt5UucPj+unzmb9pwmyME6tuWqmkMfA dRzNeni1Q==; Received: from shell.armlinux.org.uk ([fd8f:7570:feb6:1:5054:ff:fe00:4ec]:48108) by pandora.armlinux.org.uk with esmtpsa (TLS1.3:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.92) (envelope-from ) id 1mLsvQ-0001xW-IY; Thu, 02 Sep 2021 21:03:04 +0100 Received: from linux by shell.armlinux.org.uk with local (Exim 4.92) (envelope-from ) id 1mLsvN-0008Ao-SB; Thu, 02 Sep 2021 21:03:01 +0100 Date: Thu, 2 Sep 2021 21:03:01 +0100 From: "Russell King (Oracle)" To: Vladimir Oltean Cc: Vladimir Oltean , "netdev@vger.kernel.org" , Greg Kroah-Hartman , "Rafael J. Wysocki" , Andrew Lunn , Heiner Kallweit , "David S. Miller" , Jakub Kicinski , Vivien Didelot , Florian Fainelli , "linux-kernel@vger.kernel.org" , Linus Walleij , Alvin =?utf-8?Q?=C5=A0ipraga?= , ACPI Devel Maling List , kernel-team , Len Brown Subject: Re: [RFC PATCH net-next 0/3] Make the PHY library stop being so greedy when binding the generic PHY driver Message-ID: <20210902200301.GM22278@shell.armlinux.org.uk> References: <20210901225053.1205571-1-vladimir.oltean@nxp.com> <20210902121927.GE22278@shell.armlinux.org.uk> <20210902123532.ruvuecxoig67yv5v@skbuf> <20210902132635.GG22278@shell.armlinux.org.uk> <20210902152342.vett7qfhvhiyejvo@skbuf> <20210902163144.GH22278@shell.armlinux.org.uk> <20210902171033.4byfnu3g25ptnghg@skbuf> <20210902175043.GK22278@shell.armlinux.org.uk> <20210902190507.shcdmfi3v55l2zuj@skbuf> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <20210902190507.shcdmfi3v55l2zuj@skbuf> User-Agent: Mutt/1.10.1 (2018-07-13) Sender: Russell King (Oracle) Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Sep 02, 2021 at 10:05:07PM +0300, Vladimir Oltean wrote: > On Thu, Sep 02, 2021 at 06:50:43PM +0100, Russell King (Oracle) wrote: > > On Thu, Sep 02, 2021 at 05:10:34PM +0000, Vladimir Oltean wrote: > > > On Thu, Sep 02, 2021 at 05:31:44PM +0100, Russell King (Oracle) wrote: > > > > On Thu, Sep 02, 2021 at 06:23:42PM +0300, Vladimir Oltean wrote: > > > > > On Thu, Sep 02, 2021 at 02:26:35PM +0100, Russell King (Oracle) wrote: > > > > > > Debian has had support for configuring bridges at boot time via > > > > > > the interfaces file for years. Breaking that is going to upset a > > > > > > lot of people (me included) resulting in busted networks. It > > > > > > would be a sure way to make oneself unpopular. > > > > > > > > > > > > > I expect there to be 2 call paths of phy_attach_direct: > > > > > > > - At probe time. Both the MAC driver and the PHY driver are probing. > > > > > > > This is what has this patch addresses. There is no issue to return > > > > > > > -EPROBE_DEFER at that time, since drivers connect to the PHY before > > > > > > > they register their netdev. So if connecting defers, there is no > > > > > > > netdev to unregister, and user space knows nothing of this. > > > > > > > - At .ndo_open time. This is where it maybe gets interesting, but not to > > > > > > > user space. If you open a netdev and it connects to the PHY then, I > > > > > > > wouldn't expect the PHY to be undergoing a probing process, all of > > > > > > > that should have been settled by then, should it not? Where it might > > > > > > > get interesting is with NFS root, and I admit I haven't tested that. > > > > > > > > > > > > I don't think you can make that assumption. Consider the case where > > > > > > systemd is being used, DSA stuff is modular, and we're trying to > > > > > > setup a bridge device on DSA. DSA could be probing while the bridge > > > > > > is being setup. > > > > > > > > > > > > Sadly, this isn't theoretical. I've ended up needing: > > > > > > > > > > > > pre-up sleep 1 > > > > > > > > > > > > in my bridge configuration to allow time for DSA to finish probing. > > > > > > It's not a pleasant solution, nor a particularly reliable one at > > > > > > that, but it currently works around the problem. > > > > > > > > > > What problem? This is the first time I've heard of this report, and you > > > > > should definitely not need that. > > > > > > > > I found it when upgrading the Clearfog by the DSL modems to v5.13. > > > > When I rebooted it with a previously working kernel (v5.7) it has > > > > never had a problem. With v5.13, it failed to add all the lan ports > > > > into the bridge, because the bridge was still being setup by the > > > > kernel while userspace was trying to configure it. Note that I have > > > > extra debug in my kernels, hence the extra messages: > > > > > > Ok, first you talked about the interfaces file, then systemd. If it's > > > not about systemd's network manager then I don't see how it is relevant. > > > > You're reading in stuff to what I write that I did not write... I said: > > > > "Consider the case where systemd is being used, DSA stuff is modular, > > and we're trying to setup a bridge device on DSA." > > > > That does not mean I'm using systemd's network manager - which is > > something I know little about and have never used. > > You should definitely try it out, it gets a lot of new features added > all the time, it uses the netlink interface, it reacts on udev events. > > > The reason I mentioned systemd is precisely because with systemd, you > > get a hell of a lot happening parallel - and that's significiant in > > this case, because it's very clear that modules are being loaded in > > parallel with networking being brought up - and that is where the > > problems begin. In fact, modules themselves get loaded in paralllel > > with systemd. > > So that's what I don't understand. You're saying that the ifupdown > service runs in parallel with systemd-modules-load.service, and > networking is a kernel module? Doesn't that mean it behaves as expected, > then? /shrug/ > Have you tried adding an 'After=systemd-modules-load.service' dependency > to the ifupdown service? I don't think that DSA is that bad that it > registers its net devices outside of the process context in which the > insmod mv88e6xxx.ko is called. Quite the opposite, I think (but I > haven't actually taken a close look yet) that the component stuff > Saravana is proposing would do exactly that. So you "fix" one issue, you > introduce another. # systemctl list-dependencies networking.service networking.service ├─ifupdown-pre.service ├─system.slice └─network.target # systemctl list-dependencies ifupdown-pre.service ifupdown-pre.service ├─system.slice └─systemd-udevd.service Looking in the service files for a better idea: networking.service: Requires=ifupdown-pre.service Wants=network.target After=local-fs.target network-pre.target apparmor.service systemd-sysctl.service systemd-modules-load.service ifupdown-pre.service Before=network.target shutdown.target network-online.target ifupdown-pre.service: Wants=systemd-udevd.service After=systemd-udev-trigger.service Before=network.target So, the dependency you mention is already present. As is a dependency on udev. The problem is udev does all the automatic module loading asynchronously and in a multithreaded way. I don't think there's a way to make systemd wait for all module loads to complete. -- RMK's Patch system: https://www.armlinux.org.uk/developer/patches/ FTTP is here! 40Mbps down 10Mbps up. Decent connectivity at last!