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From: Vladimir Oltean <firstname.lastname@example.org> To: "Russell King (Oracle)" <email@example.com> Cc: "Vladimir Oltean" <firstname.lastname@example.org>, "email@example.com" <firstname.lastname@example.org>, "Greg Kroah-Hartman" <email@example.com>, "Rafael J. Wysocki" <firstname.lastname@example.org>, "Andrew Lunn" <email@example.com>, "Heiner Kallweit" <firstname.lastname@example.org>, "David S. Miller" <email@example.com>, "Jakub Kicinski" <firstname.lastname@example.org>, "Vivien Didelot" <email@example.com>, "Florian Fainelli" <firstname.lastname@example.org>, "email@example.com" <firstname.lastname@example.org>, "Linus Walleij" <email@example.com>, "Alvin Šipraga" <firstname.lastname@example.org>, "ACPI Devel Maling List" <email@example.com>, kernel-team <firstname.lastname@example.org>, "Len Brown" <email@example.com> Subject: Re: [RFC PATCH net-next 0/3] Make the PHY library stop being so greedy when binding the generic PHY driver Date: Thu, 2 Sep 2021 23:21:24 +0300 [thread overview] Message-ID: <20210902202124.o5lcnukdzjkbft7l@skbuf> (raw) In-Reply-To: <20210902200301.GM22278@shell.armlinux.org.uk> On Thu, Sep 02, 2021 at 09:03:01PM +0100, Russell King (Oracle) wrote: > 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. So ifupdown-pre.service has a call to "udevadm settle". This "watches the udev event queue, and exits if all current events are handled", according to the man page. But which current events? ifupdown-pre.service does not have the dependency on systemd-modules-load.service, just networking.service does. So maybe ifupdown-pre.service does not wait for DSA to finish initializing, then it tells networking.service that all is ok.
next prev parent reply other threads:[~2021-09-02 20:21 UTC|newest] Thread overview: 52+ messages / expand[flat|nested] mbox.gz Atom feed top 2021-09-01 22:50 [RFC PATCH net-next 0/3] Make the PHY library stop being so greedy when binding the generic PHY driver Vladimir Oltean 2021-09-01 22:50 ` [RFC PATCH net-next 1/3] net: phy: don't bind genphy in phy_attach_direct if the specific driver defers probe Vladimir Oltean 2021-09-02 5:43 ` Greg Kroah-Hartman 2021-09-02 10:11 ` Vladimir Oltean 2021-09-02 10:37 ` Greg Kroah-Hartman 2021-09-02 11:17 ` Vladimir Oltean 2021-09-02 14:37 ` Rafael J. Wysocki 2021-09-02 18:50 ` Russell King (Oracle) 2021-09-02 19:23 ` Vladimir Oltean 2021-09-02 19:51 ` Andrew Lunn 2021-09-02 20:33 ` Florian Fainelli 2021-09-02 21:33 ` Russell King (Oracle) 2021-09-02 21:39 ` Vladimir Oltean 2021-09-02 22:24 ` Russell King (Oracle) 2021-09-02 22:45 ` Vladimir Oltean 2021-09-02 23:02 ` Andrew Lunn 2021-09-02 23:26 ` Vladimir Oltean 2021-09-03 0:04 ` Russell King (Oracle) 2021-09-03 20:48 ` Vladimir Oltean 2021-09-03 22:06 ` Russell King (Oracle) 2021-09-04 21:59 ` Vladimir Oltean 2021-09-04 23:25 ` Russell King (Oracle) 2021-09-05 0:41 ` Vladimir Oltean 2021-09-03 9:27 ` Ioana Ciornei 2021-09-01 22:50 ` [RFC PATCH net-next 2/3] net: dsa: destroy the phylink instance on any error in dsa_slave_phy_setup Vladimir Oltean 2021-09-02 12:25 ` Russell King (Oracle) 2021-09-02 23:21 ` Florian Fainelli 2021-09-01 22:50 ` [RFC PATCH net-next 3/3] net: dsa: allow the phy_connect() call to return -EPROBE_DEFER Vladimir Oltean 2021-09-02 12:19 ` [RFC PATCH net-next 0/3] Make the PHY library stop being so greedy when binding the generic PHY driver Russell King (Oracle) 2021-09-02 12:35 ` Vladimir Oltean 2021-09-02 12:59 ` Vladimir Oltean 2021-09-02 13:26 ` Russell King (Oracle) 2021-09-02 15:23 ` Vladimir Oltean 2021-09-02 16:31 ` Russell King (Oracle) 2021-09-02 17:10 ` Vladimir Oltean 2021-09-02 17:50 ` Russell King (Oracle) 2021-09-02 19:05 ` Vladimir Oltean 2021-09-02 20:03 ` Russell King (Oracle) 2021-09-02 20:21 ` Vladimir Oltean [this message] 2021-09-02 20:29 ` Russell King (Oracle) 2021-09-03 16:22 ` Vladimir Oltean 2021-09-03 17:21 ` Andrew Lunn 2021-09-03 18:58 ` Russell King (Oracle) 2021-09-03 19:56 ` Andrew Lunn 2021-09-03 20:08 ` Russell King (Oracle) 2021-09-03 18:54 ` Russell King (Oracle) 2021-09-03 20:11 ` Vladimir Oltean 2021-09-02 20:07 ` Andrew Lunn 2021-09-02 20:32 ` Vladimir Oltean 2021-09-02 21:39 ` Russell King (Oracle) 2021-09-02 22:05 ` Vladimir Oltean 2021-09-02 23:29 ` Saravana Kannan
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