Re: [PATCH bpf-next] bpf, tcx: Skip RCU synchronization when the entry was newly created

[sashiko-bot@kernel.org]

Thank you for your contribution! Sashiko AI review found 1 potential
issue to consider:
- [Low] bpf: multi-line comment style in tcx_prog_attach() and
  tcx_link_prog_attach()
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commit 2e14928eb20fcdc45d5b96fe78599b9ad93e5381
Author: Qi Wu <shijing.wuqi@linux.alibaba.com>

bpf, tcx: Skip RCU synchronization when the entry was newly created

This commit skips calling tcx_entry_sync() in tcx_prog_attach() and
tcx_link_prog_attach() when the tcx_entry was newly created and never
published to RCU readers.

> diff --git a/kernel/bpf/tcx.c b/kernel/bpf/tcx.c
> index 02db0113b8e7c..7652069271e0c 100644
> --- a/kernel/bpf/tcx.c
> +++ b/kernel/bpf/tcx.c
> @@ -42,7 +42,11 @@ int tcx_prog_attach(const union bpf_attr *attr, struct bpf_prog *prog)
>  	if (!ret) {
>  		if (entry != entry_new) {
>  			tcx_entry_update(dev, entry_new, ingress);
> -			tcx_entry_sync();
> +			/* A newly created entry was never published, so
> +			 * there are no inflight RCU users to wait for.
> +			 */
> +			if (!created)
> +				tcx_entry_sync();
>  			tcx_skeys_inc(ingress);
>  		}
>  		bpf_mprog_commit(entry);
> @@ -156,7 +160,11 @@ static int tcx_link_prog_attach(struct bpf_link *link, u32 flags, u32 id_or_fd,
>  	if (!ret) {
>  		if (entry != entry_new) {
>  			tcx_entry_update(dev, entry_new, ingress);
> -			tcx_entry_sync();
> +			/* A newly created entry was never published, so
> +			 * there are no inflight RCU users to wait for.
> +			 */
> +			if (!created)
> +				tcx_entry_sync();
>  			tcx_skeys_inc(ingress);
>  		}
>  		bpf_mprog_commit(entry);

[Severity: Low]
This isn't a bug, but BPF code uses the multi-line comment style where the
opening /* is on its own line and the comment text starts on the next line.
Could both comments in tcx_prog_attach() and tcx_link_prog_attach() be
formatted that way?

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/20261114124039.111360-1-shijing.wuqi@linux.alibaba.com?part=1