Re: [PATCH nf-next 2/6] netfilter: nf_tables: wrap tracing with a static key

[Patrick McHardy <kaber@trash.net>]

On 24.11, Florian Westphal wrote:
> diff --git a/net/netfilter/nf_tables_core.c b/net/netfilter/nf_tables_core.c
> index 29a6ca9..dabf5ed 100644
> --- a/net/netfilter/nf_tables_core.c
> +++ b/net/netfilter/nf_tables_core.c
> @@ -138,7 +144,8 @@ next_rule:
>  		if (unlikely(rule->genmask & (1 << gencursor)))
>  			continue;
>  
> -		rulenum++;
> +		if (static_key_false(&nft_trace_enabled))
> +			rulenum++;

This API is deprecated, see Documentation/static-keys.txt.

I'm also wondering if this introduces a race condition on architectures
that don't support jump labels. static_key_slow_inc() simply increases
the ->enabled counter without further synchronization, so this might
happen while we're executing this function and some of the increments
might be skipped.