From ccbf3bfaee0e4f1ddf8103884fd4bf9f35f31f08 Mon Sep 17 00:00:00 2001 From: Eric Dumazet Date: Fri, 4 Nov 2016 11:54:31 -0700 Subject: [PATCH] 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 Signed-off-by: Yuchung Cheng Acked-by: Soheil Hassas Yeganeh Acked-by: Neal Cardwell Signed-off-by: David S. Miller --- net/ipv4/tcp.c | 41 ++++++++++++++++++++++++----------------- 1 file changed, 24 insertions(+), 17 deletions(-) diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c index 3251fe71f39f..117982be0cab 100644 --- a/net/ipv4/tcp.c +++ b/net/ipv4/tcp.c @@ -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);