Re: [PATCH V4 8/9] jump_label: Batch updates if arch supports it

[Masami Hiramatsu <mhiramat@kernel.org>]

On Mon,  4 Feb 2019 20:59:01 +0100
Daniel Bristot de Oliveira <bristot@redhat.com> wrote:

> --- a/kernel/jump_label.c
> +++ b/kernel/jump_label.c
> @@ -407,6 +407,7 @@ bool jump_label_can_update_check(struct jump_entry *entry, bool init)
>  	return 0;
>  }
>  
> +#ifndef HAVE_JUMP_LABEL_BATCH
>  static void __jump_label_update(struct static_key *key,
>  				struct jump_entry *entry,
>  				struct jump_entry *stop,
> @@ -419,6 +420,34 @@ static void __jump_label_update(struct static_key *key,
>  		}
>  	}
>  }
> +#else
> +static void __jump_label_update(struct static_key *key,
> +				struct jump_entry *entry,
> +				struct jump_entry *stop,
> +				bool init)
> +{
> +	for_each_label_entry(key, entry, stop) {
> +
> +		if (!jump_label_can_update_check(entry, init))
> +			continue;
> +
> +		if (arch_jump_label_transform_queue(entry,
> +						    jump_label_type(entry)))
> +			continue;
> +
> +		/*
> +		 * Queue's overflow: Apply the current queue, and then
> +		 * queue again. If it stills not possible to queue, BUG!
> +		 */
> +		arch_jump_label_transform_apply();
> +		if (!arch_jump_label_transform_queue(entry,
> +						     jump_label_type(entry))) {
> +			BUG();

Please do not relay on BUG(), since in both case (applied or not),
jump_label is not critical for normal operation. I think you should use
WARN_ONCE() here and lock the jump_label so that root user can report it
to us :)

Thank you,


-- 
Masami Hiramatsu <mhiramat@kernel.org>