linux-kernel - Re: [PATCH v4 2/6] driver core: Set deferred_probe_timeout to a longer default if CONFIG

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Message-ID: <CAJZ5v0jZ8VVEFjMcCMby-RdEwUY6mS5w3pMktv-hfJQ7OEp9Gg@mail.gmail.com>
Date:   Thu, 20 Feb 2020 11:36:16 +0100
From:   "Rafael J. Wysocki" <rafael@...nel.org>
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>,
        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 <linux-pm@...r.kernel.org>
Subject: Re: [PATCH v4 2/6] driver core: Set deferred_probe_timeout to a
 longer default if CONFIG_MODULES is set

On Thu, Feb 20, 2020 at 6:05 AM John Stultz <john.stultz@...aro.org> wrote:
>
> When using modules, its common for the modules not to be loaded
> until quite late by userland. With the current code,
> driver_deferred_probe_check_state() will stop returning
> EPROBE_DEFER after late_initcall, which can cause module
> dependency resolution to fail after that.
>
> So allow a longer window of 30 seconds (picked somewhat
> arbitrarily, but influenced by the similar regulator core
> timeout value) in the case where modules are enabled.
>
> Cc: Rob Herring <robh@...nel.org>
> Cc: "Rafael J. Wysocki" <rjw@...ysocki.net>
> Cc: Kevin Hilman <khilman@...nel.org>
> Cc: Ulf Hansson <ulf.hansson@...aro.org>
> Cc: Pavel Machek <pavel@....cz>
> Cc: Len Brown <len.brown@...el.com>
> Cc: Todd Kjos <tkjos@...gle.com>
> Cc: Bjorn Andersson <bjorn.andersson@...aro.org>
> Cc: Liam Girdwood <lgirdwood@...il.com>
> Cc: Mark Brown <broonie@...nel.org>
> Cc: Thierry Reding <treding@...dia.com>
> Cc: Linus Walleij <linus.walleij@...aro.org>
> Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
> Cc: linux-pm@...r.kernel.org
> Signed-off-by: John Stultz <john.stultz@...aro.org>
> Change-Id: I9c5a02a54915ff53f9f14d49c601f41d7105e05e
> ---
> v4:
> * Split out into its own patch as suggested by Mark
> * Made change conditional on CONFIG_MODULES
> ---
>  drivers/base/dd.c | 9 +++++++++
>  1 file changed, 9 insertions(+)
>
> diff --git a/drivers/base/dd.c b/drivers/base/dd.c
> index bb383dca39c1..fa138f24e2d3 100644
> --- a/drivers/base/dd.c
> +++ b/drivers/base/dd.c
> @@ -224,7 +224,16 @@ static int deferred_devs_show(struct seq_file *s, void *data)
>  }
>  DEFINE_SHOW_ATTRIBUTE(deferred_devs);
>
> +#ifdef CONFIG_MODULES
> +/*
> + * In the case of modules, set the default probe timeout to
> + * 30 seconds to give userland some time to load needed modules
> + */
> +static int deferred_probe_timeout = 30;
> +#else
> +/* In the case of !modules, no probe timeout needed */
>  static int deferred_probe_timeout = -1;
> +#endif

Looks reasonable to me.

Reviewed-by: Rafael J. Wysocki <rafael.j.wysocki@...el.com>

>  static int __init deferred_probe_timeout_setup(char *str)
>  {
>         int timeout;
> --