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tcp: annotate data-races around tp->srtt_us 

tcp_get_timestamping_opt_stats() intentionally runs lockless, we must
add READ_ONCE() and WRITE_ONCE() annotations to keep KCSAN happy.

Fixes: e8bd8fca67 ("tcp: add SRTT to SCM_TIMESTAMPING_OPT_STATS")
Signed-off-by: Eric Dumazet <edumazet@google.com>
Link: https://patch.msgid.link/20260416200319.3608680-12-edumazet@google.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
master
Eric Dumazet 2026-04-16 20:03:16 +00:00 committed by Jakub Kicinski
parent 62585690e6
commit 290b693ce7
2 changed files with 4 additions and 3 deletions
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5
net/ipv4/tcp.c
View File

@ -3623,7 +3623,8 @@ static void tcp_enable_tx_delay(struct sock *sk, int val)
if (delta && sk->sk_state == TCP_ESTABLISHED) {
s64 srtt = (s64)tp->srtt_us + delta;
tp->srtt_us = clamp_t(s64, srtt, 1, ~0U);
WRITE_ONCE(tp->srtt_us,
clamp_t(s64, srtt, 1, ~0U));
/* Note: does not deal with non zero icsk_backoff */
tcp_set_rto(sk);
@ -4467,7 +4468,7 @@ struct sk_buff *tcp_get_timestamping_opt_stats(const struct sock *sk,
READ_ONCE(tp->bytes_retrans), TCP_NLA_PAD);
nla_put_u32(stats, TCP_NLA_DSACK_DUPS, READ_ONCE(tp->dsack_dups));
nla_put_u32(stats, TCP_NLA_REORD_SEEN, READ_ONCE(tp->reord_seen));
nla_put_u32(stats, TCP_NLA_SRTT, tp->srtt_us >> 3);
nla_put_u32(stats, TCP_NLA_SRTT, READ_ONCE(tp->srtt_us) >> 3);
nla_put_u16(stats, TCP_NLA_TIMEOUT_REHASH, tp->timeout_rehash);
nla_put_u32(stats, TCP_NLA_BYTES_NOTSENT,
max_t(int, 0, tp->write_seq - tp->snd_nxt));

2
net/ipv4/tcp_input.c
View File

@ -1132,7 +1132,7 @@ static void tcp_rtt_estimator(struct sock *sk, long mrtt_us)
tcp_bpf_rtt(sk, mrtt_us, srtt);
}
tp->srtt_us = max(1U, srtt);
WRITE_ONCE(tp->srtt_us, max(1U, srtt));
}
void tcp_update_pacing_rate(struct sock *sk)