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Commit ccbf3bfa authored by Eric Dumazet's avatar Eric Dumazet Committed by David S. Miller
Browse files

tcp: shortcut listeners in tcp_get_info() 



Being lockless in tcp_get_info() is hard, because we need to add
specific synchronization in TCP fast path, like seqcount.

Following patch will change inet_diag_dump_icsk() to no longer
hold any lock for non listeners, so that we can properly acquire
socket lock in get_tcp_info() and let it return more consistent counters.

Signed-off-by: default avatarEric Dumazet <edumazet@google.com>
Signed-off-by: default avatarYuchung Cheng <ycheng@google.com>
Acked-by: default avatarSoheil Hassas Yeganeh <soheil@google.com>
Acked-by: default avatarNeal Cardwell <ncardwell@google.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 721ad321

net/ipv4/tcp.c

+24 −17
Original line number Diff line number Diff line
@@ -2721,6 +2721,27 @@ void tcp_get_info(struct sock *sk, struct tcp_info *info) 


	info->tcpi_state = sk_state_load(sk);



	/* Report meaningful fields for all TCP states, including listeners */

	rate = READ_ONCE(sk->sk_pacing_rate);

	rate64 = rate != ~0U ? rate : ~0ULL;

	put_unaligned(rate64, &info->tcpi_pacing_rate);



	rate = READ_ONCE(sk->sk_max_pacing_rate);

	rate64 = rate != ~0U ? rate : ~0ULL;

	put_unaligned(rate64, &info->tcpi_max_pacing_rate);



	info->tcpi_reordering = tp->reordering;

	info->tcpi_snd_cwnd = tp->snd_cwnd;



	if (info->tcpi_state == TCP_LISTEN) {

		/* listeners aliased fields :

		 * tcpi_unacked -> Number of children ready for accept()

		 * tcpi_sacked  -> max backlog

		 */

		info->tcpi_unacked = sk->sk_ack_backlog;

		info->tcpi_sacked = sk->sk_max_ack_backlog;

		return;

	}

	info->tcpi_ca_state = icsk->icsk_ca_state;

	info->tcpi_retransmits = icsk->icsk_retransmits;

	info->tcpi_probes = icsk->icsk_probes_out;
@@ -2748,13 +2769,9 @@ void tcp_get_info(struct sock *sk, struct tcp_info *info) 
	info->tcpi_snd_mss = tp->mss_cache;

	info->tcpi_rcv_mss = icsk->icsk_ack.rcv_mss;



	if (info->tcpi_state == TCP_LISTEN) {

		info->tcpi_unacked = sk->sk_ack_backlog;

		info->tcpi_sacked = sk->sk_max_ack_backlog;

	} else {

	info->tcpi_unacked = tp->packets_out;

	info->tcpi_sacked = tp->sacked_out;

	}



	info->tcpi_lost = tp->lost_out;

	info->tcpi_retrans = tp->retrans_out;

	info->tcpi_fackets = tp->fackets_out;
@@ -2768,23 +2785,13 @@ void tcp_get_info(struct sock *sk, struct tcp_info *info) 
	info->tcpi_rtt = tp->srtt_us >> 3;

	info->tcpi_rttvar = tp->mdev_us >> 2;

	info->tcpi_snd_ssthresh = tp->snd_ssthresh;

	info->tcpi_snd_cwnd = tp->snd_cwnd;

	info->tcpi_advmss = tp->advmss;

	info->tcpi_reordering = tp->reordering;



	info->tcpi_rcv_rtt = jiffies_to_usecs(tp->rcv_rtt_est.rtt)>>3;

	info->tcpi_rcv_space = tp->rcvq_space.space;



	info->tcpi_total_retrans = tp->total_retrans;



	rate = READ_ONCE(sk->sk_pacing_rate);

	rate64 = rate != ~0U ? rate : ~0ULL;

	put_unaligned(rate64, &info->tcpi_pacing_rate);



	rate = READ_ONCE(sk->sk_max_pacing_rate);

	rate64 = rate != ~0U ? rate : ~0ULL;

	put_unaligned(rate64, &info->tcpi_max_pacing_rate);



	do {

		start = u64_stats_fetch_begin_irq(&tp->syncp);

		put_unaligned(tp->bytes_acked, &info->tcpi_bytes_acked);