Re: [PATCH net-next 2/5] netdev-genl: Dump napi_defer_hard_irqs

Jakub Kicinski
2024-08-29T22:08:30Z

On Thu, 29 Aug 2024 13:11:58 +0000 Joe Damato wrote:
> diff --git a/Documentation/netlink/specs/netdev.yaml b/Documentation/netlink/specs/netdev.yaml
> index 959755be4d7f..ee4f99fd4574 100644
> --- a/Documentation/netlink/specs/netdev.yaml
> +++ b/Documentation/netlink/specs/netdev.yaml
> @@ -244,6 +244,11 @@ attribute-sets:
> threaded mode. If NAPI is not in threaded mode (i.e. uses normal
> softirq context), the attribute will be absent.
> type: u32
> + -
> + name: defer-hard-irqs
> + doc: The number of consecutive empty polls before IRQ deferral ends
> + and hardware IRQs are re-enabled.
> + type: s32

Why is this a signed value? 🤔️
You can use:

check:
max: s32-max

to have netlink validate the overflow if you switch to u32.

> -
> name: queue
> attributes:

> @@ -188,6 +189,10 @@ netdev_nl_napi_fill_one(struct sk_buff *rsp, struct napi_struct *napi,
> goto nla_put_failure;
> }
>
> + napi_defer_hard_irqs = napi_get_defer_hard_irqs(napi);

Here, for example the READ_ONCE() wouldn't have been necessary, right?
Cause we are holding rtnl_lock(), just a random thought, not really
actionable.

> + if (nla_put_s32(rsp, NETDEV_A_NAPI_DEFER_HARD_IRQS, napi_defer_hard_irqs))
> + goto nla_put_failure;