linux-kernel - Re: [PATCH v1] module: Add support for default value for module async

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Date:   Fri, 3 Jun 2022 08:01:46 -0700
From:   Luis Chamberlain <mcgrof@...nel.org>
To:     Saravana Kannan <saravanak@...gle.com>,
        Dmitry Torokhov <dmitry.torokhov@...il.com>
Cc:     Jonathan Corbet <corbet@....net>, kernel-team@...roid.com,
        linux-doc@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-modules@...r.kernel.org
Subject: Re: [PATCH v1] module: Add support for default value for module
 async_probe

On Thu, Jun 02, 2022 at 10:54:41PM -0700, Saravana Kannan 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>
> ---
>  Documentation/admin-guide/kernel-parameters.txt |  8 ++++++--
>  kernel/module/main.c                            | 11 ++++++++++-
>  2 files changed, 16 insertions(+), 3 deletions(-)
> 
> diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
> index 710b52d87bdd..32083056bd25 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.

The commit log says a bit more. Can you clarify this on the
documentation?

We should strive slowly towards more async probes. This will take
time. To help with further then a Kconfig option which sets this
to a default to true if enabled would be useful so that no kernel
parameter is needed at all to set the default. Then you can
override the default, and blacklist each driver as well.

  Luis