netdev - Re: [PATCH v4 bpf-next 4/6] bpf: udp: Avoid socket skips and repeats during iteration

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Message-ID: <11f8a2b3-ad4d-4e59-b537-61e1381de692@linux.dev>
Date: Mon, 21 Apr 2025 20:47:51 -0700
From: Martin KaFai Lau <martin.lau@...ux.dev>
To: Jordan Rife <jordan@...fe.io>
Cc: Aditi Ghag <aditi.ghag@...valent.com>,
 Daniel Borkmann <daniel@...earbox.net>,
 Willem de Bruijn <willemdebruijn.kernel@...il.com>,
 Kuniyuki Iwashima <kuniyu@...zon.com>, netdev@...r.kernel.org,
 bpf@...r.kernel.org
Subject: Re: [PATCH v4 bpf-next 4/6] bpf: udp: Avoid socket skips and repeats
 during iteration

On 4/19/25 8:58 AM, Jordan Rife wrote:
>   static void bpf_iter_udp_put_batch(struct bpf_udp_iter_state *iter)
>   {
> -	while (iter->cur_sk < iter->end_sk)
> -		sock_put(iter->batch[iter->cur_sk++].sock);
> +	union bpf_udp_iter_batch_item *item;
> +	unsigned int cur_sk = iter->cur_sk;
> +	__u64 cookie;
> +
> +	/* Remember the cookies of the sockets we haven't seen yet, so we can
> +	 * pick up where we left off next time around.
> +	 */
> +	while (cur_sk < iter->end_sk) {
> +		item = &iter->batch[cur_sk++];
> +		cookie = __sock_gen_cookie(item->sock);

This can be called in the start/stop which is preemptible. I suspect this should 
be sock_gen_cookie instead of __sock_gen_cookie. gen_cookie_next() is using 
this_cpu_ptr.

> +		sock_put(item->sock);
> +		item->cookie = cookie;
> +	}
>   }