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Message-ID: <CAMuHMdVrWotHv5qTW0j_=uZsmwv7Vrkg-rm-=U=YbffsSfwfCg@mail.gmail.com>
Date: Wed, 16 Aug 2023 12:10:53 +0200
From: Geert Uytterhoeven <geert@...ux-m68k.org>
To: Shreeya Patel <shreeya.patel@...labora.com>
Cc: saravanak@...gle.com,
Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
stable@...r.kernel.org, John Stultz <jstultz@...gle.com>,
"David S. Miller" <davem@...emloft.net>,
Alexey Kuznetsov <kuznet@....inr.ac.ru>,
Hideaki YOSHIFUJI <yoshfuji@...ux-ipv6.org>,
Jakub Kicinski <kuba@...nel.org>,
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>,
linux-pm@...r.kernel.org, Nathan Chancellor <nathan@...nel.org>,
Sebastian Andrzej Siewior <bigeasy@...utronix.de>,
Geert Uytterhoeven <geert+renesas@...der.be>,
"Rafael J. Wysocki" <rafael@...nel.org>,
Linus Torvalds <torvalds@...ux-foundation.org>,
Sasha Levin <sashal@...nel.org>, linux-kernel@...r.kernel.org,
"gustavo.padovan@...labora.com" <gustavo.padovan@...labora.com>,
Ricardo Cañuelo Navarro
<ricardo.canuelo@...labora.com>,
Guillaume Charles Tucker <guillaume.tucker@...labora.com>,
usama.anjum@...labora.com, kernelci@...ts.linux.dev
Subject: Re: [PATCH 5.17 127/298] driver core: Fix wait_for_device_probe() &
deferred_probe_timeout interaction
Hi Shreeya,
On Wed, Aug 16, 2023 at 11:39 AM Shreeya Patel
<shreeya.patel@...labora.com> wrote:
> On 13/06/22 15:40, Greg Kroah-Hartman wrote:
> > From: Saravana Kannan<saravanak@...gle.com>
> >
> > [ Upstream commit 5ee76c256e928455212ab759c51d198fedbe7523 ]
> >
> > Mounting NFS rootfs was timing out when deferred_probe_timeout was
> > non-zero [1]. This was because ip_auto_config() initcall times out
> > waiting for the network interfaces to show up when
> > deferred_probe_timeout was non-zero. While ip_auto_config() calls
> > wait_for_device_probe() to make sure any currently running deferred
> > probe work or asynchronous probe finishes, that wasn't sufficient to
> > account for devices being deferred until deferred_probe_timeout.
> >
> > Commit 35a672363ab3 ("driver core: Ensure wait_for_device_probe() waits
> > until the deferred_probe_timeout fires") tried to fix that by making
> > sure wait_for_device_probe() waits for deferred_probe_timeout to expire
> > before returning.
> >
> > However, if wait_for_device_probe() is called from the kernel_init()
> > context:
> >
> > - Before deferred_probe_initcall() [2], it causes the boot process to
> > hang due to a deadlock.
> >
> > - After deferred_probe_initcall() [3], it blocks kernel_init() from
> > continuing till deferred_probe_timeout expires and beats the point of
> > deferred_probe_timeout that's trying to wait for userspace to load
> > modules.
> >
> > Neither of this is good. So revert the changes to
> > wait_for_device_probe().
> >
> > [1] -https://lore.kernel.org/lkml/TYAPR01MB45443DF63B9EF29054F7C41FD8C60@TYAPR01MB4544.jpnprd01.prod.outlook.com/
> > [2] -https://lore.kernel.org/lkml/YowHNo4sBjr9ijZr@dev-arch.thelio-3990X/
> > [3] -https://lore.kernel.org/lkml/Yo3WvGnNk3LvLb7R@linutronix.de/
>
> Hi Saravana, Greg,
>
>
> KernelCI found this patch causes the baseline.bootrr.deferred-probe-empty test to fail on r8a77960-ulcb,
> see the following details for more information.
Commit 9be4cbd09da820a2 ("driver core: Set default deferred_probe_timeout
back to 0.") in v5.19 contains a reference to the same commit as
mentioned in the Fixes tag. Does backporting that help?
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
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