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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: Eric Dumazet <edumazet@google.com>
Signed-off-by: Yuchung Cheng <ycheng@google.com>
Acked-by: Soheil Hassas Yeganeh <soheil@google.com>
Acked-by: Neal Cardwell <ncardwell@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Eric Dumazet 2016-11-04 11:54:31 -07:00 committed by David S. Miller
parent 721ad32144
commit ccbf3bfaee
1 changed files with 24 additions and 17 deletions
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41
net/ipv4/tcp.c
View File

@ -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_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);