linux-kernel - Re: [PATCH v5 0/6] driver core: Improve and cleanup driver_deferred_probe_check

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Date:   Wed, 22 Apr 2020 01:59:14 +0200
From:   Eugeniu Rosca <erosca@...adit-jv.com>
To:     John Stultz <john.stultz@...aro.org>
CC:     lkml <linux-kernel@...r.kernel.org>, Rob Herring <robh@...nel.org>,
        "Rafael J. Wysocki" <rjw@...ysocki.net>,
        Kevin Hilman <khilman@...nel.org>,
        Ulf Hansson <ulf.hansson@...aro.org>,
        Pavel Machek <pavel@....cz>, Len Brown <len.brown@...el.com>,
        Todd Kjos <tkjos@...gle.com>,
        Saravana Kannan <saravanak@...gle.com>,
        Bjorn Andersson <bjorn.andersson@...aro.org>,
        Liam Girdwood <lgirdwood@...il.com>,
        Mark Brown <broonie@...nel.org>,
        Thierry Reding <treding@...dia.com>,
        Linus Walleij <linus.walleij@...aro.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        <linux-pm@...r.kernel.org>, <linux-renesas-soc@...r.kernel.org>,
        Eugeniu Rosca <erosca@...adit-jv.com>,
        Eugeniu Rosca <roscaeugeniu@...il.com>
Subject: Re: [PATCH v5 0/6] driver core: Improve and cleanup
 driver_deferred_probe_check_state()

Hi John,
Cc: linux-renesas-soc

On Tue, Feb 25, 2020 at 05:08:22AM +0000, John Stultz wrote:
> This series goal is to improve and cleanup the
> driver_deferred_probe_check_state() code in the driver core.
> 
> This series is useful for being able to support modules
> dependencies which may be loaded by userland, far after
> late_initcall is done. For instance, this series allows us to
> successfully use various clk drivers as modules on the db845c
> board. And without it, those drivers have to be statically built
> in to work.
> 
> Since I first sent out this patch, Saravana suggested an
> alternative approach which also works for our needs, and is a
> bit simpler:
>  https://lore.kernel.org/lkml/20200220055250.196456-1-saravanak@google.com/T/#u
> 
> However, while that patch provides the functionality we need,
> I still suspect the driver_deferred_probe_check_state() code
> could benefit from the cleanup in this patch, as the existing
> logic is somewhat muddy.
> 
> New in v5:
> * Reworked the driver_deferred_probe_check_state() logic as
>   suggested by Saravana to tie the initcall_done checking with
>   modules being enabled.
> * Cleanup some comment wording as suggested by Rafael
> * Try to slightly simplify the regulator logic as suggested by
>   Bjorn
> 
> Thanks so much to Bjorn, Saravana and Rafael for their reviews
> and suggestions! Additional review and feedback is always greatly
> appreciated!

Building a recent [0] kernel using vanilla arm64 defconfig
and booting it on H3ULCB, I get buried into backtraces [1].

After reverting this series, up to and including its first commit,
booting goes back to normal [2].

Any chance to get a fix or at least some hints where to dig into?

[0] https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=18bf34080c4c3b
    ("Merge branch 'akpm' (patches from Andrew)")
[1] https://gist.github.com/erosca/ac779c348dd272c448e162c406c48f4a
[2] https://gist.github.com/erosca/5eea2bc5e82be651d405ba038d0ad036

-- 
Best regards,
Eugeniu Rosca