netdev - Re: [PATCH net-next v2 4/5] ptp: Support late timestamp determination

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Date:   Sun, 10 Apr 2022 00:29:30 -0700
From:   Richard Cochran <richardcochran@...il.com>
To:     Gerhard Engleder <gerhard@...leder-embedded.com>
Cc:     vinicius.gomes@...el.com, yangbo.lu@....com, davem@...emloft.net,
        kuba@...nel.org, mlichvar@...hat.com, netdev@...r.kernel.org
Subject: Re: [PATCH net-next v2 4/5] ptp: Support late timestamp determination

On Sun, Apr 03, 2022 at 07:55:43PM +0200, Gerhard Engleder wrote:

> @@ -887,18 +885,28 @@ void __sock_recv_timestamp(struct msghdr *msg, struct sock *sk,
>  	if (shhwtstamps &&
>  	    (sk->sk_tsflags & SOF_TIMESTAMPING_RAW_HARDWARE) &&
>  	    !skb_is_swtx_tstamp(skb, false_tstamp)) {
> +		rcu_read_lock();
> +		orig_dev = dev_get_by_napi_id(skb_napi_id(skb));

__sock_recv_timestamp() is hot path.

No need to call dev_get_by_napi_id() for the vast majority of cases
using plain old MAC time stamping.

Make this conditional on (sk->sk_tsflags & SOF_TIMESTAMPING_BIND_PHC).

Thanks,
Richard

> +		if (orig_dev) {
> +			if_index = orig_dev->ifindex;
> +			hwtstamp = netdev_get_tstamp(orig_dev, shhwtstamps,
> +						     sk->sk_tsflags & SOF_TIMESTAMPING_BIND_PHC);
> +		} else {
> +			if_index = 0;
> +			hwtstamp = shhwtstamps->hwtstamp;
> +		}
> +		rcu_read_unlock();
> +
>  		if (sk->sk_tsflags & SOF_TIMESTAMPING_BIND_PHC)
> -			hwtstamp = ptp_convert_timestamp(&shhwtstamps->hwtstamp,
> +			hwtstamp = ptp_convert_timestamp(&hwtstamp,
>  							 sk->sk_bind_phc);
> -		else
> -			hwtstamp = shhwtstamps->hwtstamp;
>  
>  		if (ktime_to_timespec64_cond(hwtstamp, tss.ts + 2)) {
>  			empty = 0;
>  
>  			if ((sk->sk_tsflags & SOF_TIMESTAMPING_OPT_PKTINFO) &&
>  			    !skb_is_err_queue(skb))
> -				put_ts_pktinfo(msg, skb);
> +				put_ts_pktinfo(msg, skb, if_index);
>  		}
>  	}
>  	if (!empty) {
> -- 
> 2.20.1
>