linux-kernel - Re: [PATCH] dd: Invoke one probe retry cycle after every initcall level

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Date:   Mon, 23 Jul 2018 13:17:07 +0200
From:   "Rafael J. Wysocki" <rafael@...nel.org>
To:     Rishabh Bhatnagar <rishabhb@...eaurora.org>
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        ckadabi@...eaurora.org, tsoni@...eaurora.org,
        Vikram Mulukutla <markivx@...eaurora.org>
Subject: Re: [PATCH] dd: Invoke one probe retry cycle after every initcall level

On Thu, Jul 19, 2018 at 11:24 PM, Rishabh Bhatnagar
<rishabhb@...eaurora.org> wrote:
> Drivers that are registered at an initcall level may have to
> wait until late_init before the probe deferral mechanism can
> retry their probe functions. It is possible that their
> dependencies were resolved much earlier, in some cases even
> before the next initcall level. Invoke one probe retry cycle
> at every _sync initcall level, allowing these drivers to be
> probed earlier.

Can you please say something about the actual use case this is
expected to address?

> Signed-off-by: Vikram Mulukutla <markivx@...eaurora.org>
> Signed-off-by: Rishabh Bhatnagar <rishabhb@...eaurora.org>
> ---
>  drivers/base/dd.c | 33 +++++++++++++++++++++++++++------
>  1 file changed, 27 insertions(+), 6 deletions(-)
>
> diff --git a/drivers/base/dd.c b/drivers/base/dd.c
> index 1435d72..e6a6821 100644
> --- a/drivers/base/dd.c
> +++ b/drivers/base/dd.c
> @@ -224,23 +224,44 @@ void device_unblock_probing(void)
>         driver_deferred_probe_trigger();
>  }
>
> +static void enable_trigger_defer_cycle(void)
> +{
> +       driver_deferred_probe_enable = true;
> +       driver_deferred_probe_trigger();
> +       /*
> +        * Sort as many dependencies as possible before the next initcall
> +        * level
> +        */
> +       flush_work(&deferred_probe_work);
> +}
> +
>  /**
>   * deferred_probe_initcall() - Enable probing of deferred devices
>   *
>   * We don't want to get in the way when the bulk of drivers are getting probed.
>   * Instead, this initcall makes sure that deferred probing is delayed until
> - * late_initcall time.
> + * all the registered initcall functions at a particular level are completed.
> + * This function is invoked at every *_initcall_sync level.
>   */
>  static int deferred_probe_initcall(void)
>  {
> -       driver_deferred_probe_enable = true;
> -       driver_deferred_probe_trigger();
> -       /* Sort as many dependencies as possible before exiting initcalls */
> -       flush_work(&deferred_probe_work);
> +       enable_trigger_defer_cycle();
> +       driver_deferred_probe_enable = false;
> +       return 0;
> +}
> +arch_initcall_sync(deferred_probe_initcall);
> +subsys_initcall_sync(deferred_probe_initcall);
> +fs_initcall_sync(deferred_probe_initcall);
> +device_initcall_sync(deferred_probe_initcall);
> +
> +static int deferred_probe_enable_fn(void)
> +{
> +       /* Enable deferred probing for all time */
> +       enable_trigger_defer_cycle();
>         initcalls_done = true;
>         return 0;
>  }
> -late_initcall(deferred_probe_initcall);
> +late_initcall(deferred_probe_enable_fn);
>
>  /**
>   * device_is_bound() - Check if device is bound to a driver
> --
> The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum,
> a Linux Foundation Collaborative Project