linux-kernel - Re: [PATCH v2] module: Add support for default value for module async

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Date:   Wed, 15 Jun 2022 20:19:34 -0700
From:   Saravana Kannan <saravanak@...gle.com>
To:     Jonathan Corbet <corbet@....net>,
        Luis Chamberlain <mcgrof@...nel.org>
Cc:     kernel-team@...roid.com, linux-doc@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-modules@...r.kernel.org
Subject: Re: [PATCH v2] module: Add support for default value for module async_probe

On Fri, Jun 3, 2022 at 6:01 PM Saravana Kannan <saravanak@...gle.com> wrote:
>
> Add a module.async_probe kernel command line option that allows enabling
> async probing for all modules. When this command line option is used,
> there might still be some modules for which we want to explicitly force
> synchronous probing, so extend <modulename>.async_probe to take an
> optional bool input so that async probing can be disabled for a specific
> module.
>
> Signed-off-by: Saravana Kannan <saravanak@...gle.com>
> ---
> v1->v2:
> - Updated the documentation to capture all the details/changes.

Luis,

Gentle reminder.

-Saravana

>
>  Documentation/admin-guide/kernel-parameters.txt | 17 +++++++++++++++--
>  kernel/module/main.c                            | 11 ++++++++++-
>  2 files changed, 25 insertions(+), 3 deletions(-)
>
> diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
> index 710b52d87bdd..5174a08e20b0 100644
> --- a/Documentation/admin-guide/kernel-parameters.txt
> +++ b/Documentation/admin-guide/kernel-parameters.txt
> @@ -1147,8 +1147,12 @@
>         nopku           [X86] Disable Memory Protection Keys CPU feature found
>                         in some Intel CPUs.
>
> -       <module>.async_probe [KNL]
> -                       Enable asynchronous probe on this module.
> +       <module>.async_probe[=<bool>] [KNL]
> +                       If no <bool> value is specified or if the value
> +                       specified is not a valid <bool>, enable asynchronous
> +                       probe on this module.  Otherwise, enable/disable
> +                       asynchronous probe on this module as indicated by the
> +                       <bool> value. See also: module.async_probe
>
>         early_ioremap_debug [KNL]
>                         Enable debug messages in early_ioremap support. This
> @@ -3201,6 +3205,15 @@
>                         log everything. Information is printed at KERN_DEBUG
>                         so loglevel=8 may also need to be specified.
>
> +       module.async_probe=<bool>
> +                       [KNL] When set to true, modules will use async probing
> +                       by default. To enable/disable async probing for a
> +                       specific module, use the module specific control that
> +                       is documented under <module>.async_probe. When both
> +                       module.async_probe and <module>.async_probe are
> +                       specified, <module>.async_probe takes precedence for
> +                       the specific module.
> +
>         module.sig_enforce
>                         [KNL] When CONFIG_MODULE_SIG is set, this means that
>                         modules without (valid) signatures will fail to load.
> diff --git a/kernel/module/main.c b/kernel/module/main.c
> index fed58d30725d..47085795f037 100644
> --- a/kernel/module/main.c
> +++ b/kernel/module/main.c
> @@ -2410,6 +2410,12 @@ static void do_free_init(struct work_struct *w)
>         }
>  }
>
> +#undef MODULE_PARAM_PREFIX
> +#define MODULE_PARAM_PREFIX "module."
> +/* Default value for module->async_probe_requested */
> +static bool async_probe;
> +module_param(async_probe, bool, 0644);
> +
>  /*
>   * This is where the real work happens.
>   *
> @@ -2630,7 +2636,8 @@ static int unknown_module_param_cb(char *param, char *val, const char *modname,
>         int ret;
>
>         if (strcmp(param, "async_probe") == 0) {
> -               mod->async_probe_requested = true;
> +               if (strtobool(val, &mod->async_probe_requested))
> +                       mod->async_probe_requested = true;
>                 return 0;
>         }
>
> @@ -2797,6 +2804,8 @@ static int load_module(struct load_info *info, const char __user *uargs,
>         if (err)
>                 goto bug_cleanup;
>
> +       mod->async_probe_requested = async_probe;
> +
>         /* Module is ready to execute: parsing args may do that. */
>         after_dashes = parse_args(mod->name, mod->args, mod->kp, mod->num_kp,
>                                   -32768, 32767, mod,
> --
> 2.36.1.255.ge46751e96f-goog
>