Re: [PATCH net-next v2 06/18] netfilter: nf_dup{4, 6}: Move duplication check to task_struct

[Peter Zijlstra <peterz@infradead.org>]

On Mon, Apr 14, 2025 at 06:07:42PM +0200, Sebastian Andrzej Siewior wrote:
> nf_skb_duplicated is a per-CPU variable and relies on disabled BH for its
> locking. Without per-CPU locking in local_bh_disable() on PREEMPT_RT
> this data structure requires explicit locking.
> 
> Due to the recursion involved, the simplest change is to make it a
> per-task variable.
> 
> Move the per-CPU variable nf_skb_duplicated to task_struct and name it
> in_nf_duplicate. Add it to the existing bitfield so it doesn't use
> additional memory.
> 
> Cc: Pablo Neira Ayuso <pablo@netfilter.org>
> Cc: Jozsef Kadlecsik <kadlec@netfilter.org>
> Cc: Ingo Molnar <mingo@redhat.com>
> Cc: Peter Zijlstra <peterz@infradead.org>
> Cc: Juri Lelli <juri.lelli@redhat.com>
> Cc: Vincent Guittot <vincent.guittot@linaro.org>
> Cc: Dietmar Eggemann <dietmar.eggemann@arm.com>
> Cc: Steven Rostedt <rostedt@goodmis.org>
> Cc: Ben Segall <bsegall@google.com>
> Cc: Mel Gorman <mgorman@suse.de>
> Cc: Valentin Schneider <vschneid@redhat.com>
> Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
> ---
>  include/linux/netfilter.h        | 11 -----------
>  include/linux/sched.h            |  1 +
>  net/ipv4/netfilter/ip_tables.c   |  2 +-
>  net/ipv4/netfilter/nf_dup_ipv4.c |  6 +++---
>  net/ipv6/netfilter/ip6_tables.c  |  2 +-
>  net/ipv6/netfilter/nf_dup_ipv6.c |  6 +++---
>  net/netfilter/core.c             |  3 ---
>  7 files changed, 9 insertions(+), 22 deletions(-)

Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>