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In-Reply-To: <Yo3WvGnNk3LvLb7R@linutronix.de>
From:   Saravana Kannan <saravanak@google.com>
Date:   Wed, 25 May 2022 12:49:00 -0700
Message-ID: <CAGETcx84ja_w_=vXKDOZnM8EVEcuAg1tX9Kqy57PTkDb1=H4FA@mail.gmail.com>
Subject: Re: [PATCH v1] driver core: Extend deferred probe timeout on driver registration
To:     Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Cc:     Nathan Chancellor <nathan@kernel.org>,
        Jonathan Corbet <corbet@lwn.net>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        "Rafael J. Wysocki" <rafael@kernel.org>,
        "Rafael J. Wysocki" <rjw@rjwysocki.net>,
        Rob Herring <robh@kernel.org>,
        Linus Walleij <linus.walleij@linaro.org>,
        Will Deacon <will@kernel.org>,
        Ulf Hansson <ulf.hansson@linaro.org>,
        Kevin Hilman <khilman@kernel.org>,
        Thierry Reding <treding@nvidia.com>,
        Mark Brown <broonie@kernel.org>, Pavel Machek <pavel@ucw.cz>,
        Geert Uytterhoeven <geert@linux-m68k.org>,
        Yoshihiro Shimoda <yoshihiro.shimoda.uh@renesas.com>,
        Paul Kocialkowski <paul.kocialkowski@bootlin.com>,
        linux-gpio@vger.kernel.org, linux-pm@vger.kernel.org,
        iommu@lists.linux-foundation.org, kernel-team@android.com,
        linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org,
        linux-s390@vger.kernel.org, John Stultz <jstultz@google.com>
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On Wed, May 25, 2022 at 12:12 AM Sebastian Andrzej Siewior
<bigeasy@linutronix.de> wrote:
>
> On 2022-05-24 10:46:49 [-0700], Saravana Kannan wrote:
> > > Removing probe_timeout_waitqueue (as suggested) or setting the timeou=
t
> > > to 0 avoids the delay.
> >
> > In your case, I think it might be working as intended? Curious, what
> > was the call stack in your case where it was blocked?
>
> Why is then there 10sec delay during boot? The backtrace is
> |------------[ cut here ]------------
> |WARNING: CPU: 4 PID: 1 at drivers/base/dd.c:742 wait_for_device_probe+0x=
30/0x110
> |Modules linked in:
> |CPU: 4 PID: 1 Comm: swapper/0 Not tainted 5.18.0-rc5+ #154
> |RIP: 0010:wait_for_device_probe+0x30/0x110
> |Call Trace:
> | <TASK>
> | prepare_namespace+0x2b/0x160
> | kernel_init_freeable+0x2b3/0x2dd
> | kernel_init+0x11/0x110
> | ret_from_fork+0x22/0x30
> | </TASK>
>
> Looking closer, it can't access init. This in particular box boots
> directly the kernel without an initramfs so the kernel later mounts
> /dev/sda1 and everything is good.  So that seems to be the reason=E2=80=
=A6

Hmmm... that part shouldn't matter. As long as you are hitting the
same code path. My guess is one of them has CONFIG_MODULES enabled and
the other doesn't.

In either case, I think the patch needs to be reverted (I'll send out
one soon), but that'll also mean I need to revert part of my patch
(sets the timeout back to 0) or I need to fix this case:
https://lore.kernel.org/lkml/TYAPR01MB45443DF63B9EF29054F7C41FD8C60@TYAPR01=
MB4544.jpnprd01.prod.outlook.com/

I'll try to do the latter if I can get something reasonable soon.
Otherwise, I'll just do the revert + partial revert.

-Saravana


> My other machine with an initramfs does not show this problem.
>
> > -Saravana
>
> Sebastian