netdev - Re: [PATCH v3 1/3] driver core: Revert default driver_deferred_probe

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Date:   Thu, 23 Apr 2020 09:23:09 +0200
From:   Geert Uytterhoeven <geert@...ux-m68k.org>
To:     John Stultz <john.stultz@...aro.org>
Cc:     lkml <linux-kernel@...r.kernel.org>,
        "David S. Miller" <davem@...emloft.net>,
        Alexey Kuznetsov <kuznet@....inr.ac.ru>,
        Hideaki YOSHIFUJI <yoshfuji@...ux-ipv6.org>,
        Jakub Kicinski <kuba@...nel.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        "Rafael J . Wysocki" <rjw@...ysocki.net>,
        Rob Herring <robh@...nel.org>,
        Yoshihiro Shimoda <yoshihiro.shimoda.uh@...esas.com>,
        Robin Murphy <robin.murphy@....com>,
        Andy Shevchenko <andy.shevchenko@...il.com>,
        Sudeep Holla <sudeep.holla@....com>,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        Naresh Kamboju <naresh.kamboju@...aro.org>,
        Basil Eljuse <Basil.Eljuse@....com>,
        Ferry Toth <fntoth@...il.com>, Arnd Bergmann <arnd@...db.de>,
        Anders Roxell <anders.roxell@...aro.org>,
        netdev <netdev@...r.kernel.org>,
        Linux PM list <linux-pm@...r.kernel.org>
Subject: Re: [PATCH v3 1/3] driver core: Revert default driver_deferred_probe_timeout
 value to 0

Hi John,

On Wed, Apr 22, 2020 at 10:33 PM John Stultz <john.stultz@...aro.org> wrote:
> This patch addresses a regression in 5.7-rc1+
>
> In commit c8c43cee29f6 ("driver core: Fix
> driver_deferred_probe_check_state() logic"), we both cleaned up
> the logic and also set the default driver_deferred_probe_timeout
> value to 30 seconds to allow for drivers that are missing
> dependencies to have some time so that the dependency may be
> loaded from userland after initcalls_done is set.
>
> However, Yoshihiro Shimoda reported that on his device that
> expects to have unmet dependencies (due to "optional links" in
> its devicetree), was failing to mount the NFS root.
>
> In digging further, it seemed the problem was that while the
> device properly probes after waiting 30 seconds for any missing
> modules to load, the ip_auto_config() had already failed,
> resulting in NFS to fail. This was due to ip_auto_config()
> calling wait_for_device_probe() which doesn't wait for the
> driver_deferred_probe_timeout to fire.
>
> Fixing that issue is possible, but could also introduce 30
> second delays in bootups for users who don't have any
> missing dependencies, which is not ideal.
>
> So I think the best solution to avoid any regressions is to
> revert back to a default timeout value of zero, and allow
> systems that need to utilize the timeout in order for userland
> to load any modules that supply misisng dependencies in the dts
> to specify the timeout length via the exiting documented boot
> argument.
>
> Thanks to Geert for chasing down that ip_auto_config was why NFS
> was failing in this case!
>
> Cc: "David S. Miller" <davem@...emloft.net>
> Cc: Alexey Kuznetsov <kuznet@....inr.ac.ru>
> Cc: Hideaki YOSHIFUJI <yoshfuji@...ux-ipv6.org>
> Cc: Jakub Kicinski <kuba@...nel.org>
> Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
> Cc: Rafael J. Wysocki <rjw@...ysocki.net>
> Cc: Rob Herring <robh@...nel.org>
> Cc: Geert Uytterhoeven <geert@...ux-m68k.org>
> Cc: Yoshihiro Shimoda <yoshihiro.shimoda.uh@...esas.com>
> Cc: Robin Murphy <robin.murphy@....com>
> Cc: Andy Shevchenko <andy.shevchenko@...il.com>
> Cc: Sudeep Holla <sudeep.holla@....com>
> Cc: Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
> Cc: Naresh Kamboju <naresh.kamboju@...aro.org>
> Cc: Basil Eljuse <Basil.Eljuse@....com>
> Cc: Ferry Toth <fntoth@...il.com>
> Cc: Arnd Bergmann <arnd@...db.de>
> Cc: Anders Roxell <anders.roxell@...aro.org>
> Cc: netdev <netdev@...r.kernel.org>
> Cc: linux-pm@...r.kernel.org
> Reported-by: Yoshihiro Shimoda <yoshihiro.shimoda.uh@...esas.com>
> Tested-by: Yoshihiro Shimoda <yoshihiro.shimoda.uh@...esas.com>
> Fixes: c8c43cee29f6 ("driver core: Fix driver_deferred_probe_check_state() logic")
> Signed-off-by: John Stultz <john.stultz@...aro.org>

Looks like you lost my
Tested-by: Geert Uytterhoeven <geert+renesas@...der.be>
on v2.

Gr{oetje,eeting}s,

                        Geert

-- 
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@...ux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds