tcp: remove READ_ONCE(req->ts_recent)

After commit 8d52da2 ("tcp: Defer ts_recent changes
until req is owned"), req->ts_recent is not changed anymore.

It is set once in tcp_openreq_init(), bpf_sk_assign_tcp_reqsk()
or cookie_tcp_reqsk_alloc() before the req can be seen by other
cpus/threads.

This completes the revert of eba2081 ("tcp: annotate
data-races around tcp_rsk(req)->ts_recent").

Signed-off-by: Eric Dumazet <edumazet@google.com>
Cc: Wang Hai <wanghai38@huawei.com>
Reviewed-by: Jason Xing <kerneljasonxing@gmail.com>
Reviewed-by: Kuniyuki Iwashima <kuniyu@amazon.com>
Link: https://patch.msgid.link/20250301201424.2046477-6-edumazet@google.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

net/ipv4/tcp_ipv4.c

@@ -1155,7 +1155,7 @@ static void tcp_v4_reqsk_send_ack(const struct sock *sk, struct sk_buff *skb,
 			tcp_rsk(req)->rcv_nxt,
 			tcp_synack_window(req) >> inet_rsk(req)->rcv_wscale,
 			tcp_rsk_tsval(tcp_rsk(req)),
-			READ_ONCE(req->ts_recent),
+			req->ts_recent,
 			0, &key,
 			inet_rsk(req)->no_srccheck ? IP_REPLY_ARG_NOSRCCHECK : 0,
 			ip_hdr(skb)->tos,

net/ipv4/tcp_minisocks.c

@@ -585,7 +585,7 @@ struct sock *tcp_create_openreq_child(const struct sock *sk,
 
 	if (newtp->rx_opt.tstamp_ok) {
 		newtp->tcp_usec_ts = treq->req_usec_ts;
-		newtp->rx_opt.ts_recent = READ_ONCE(req->ts_recent);
+		newtp->rx_opt.ts_recent = req->ts_recent;
 		newtp->rx_opt.ts_recent_stamp = ktime_get_seconds();
 		newtp->tcp_header_len = sizeof(struct tcphdr) + TCPOLEN_TSTAMP_ALIGNED;
 	} else {
@@ -673,7 +673,7 @@ struct sock *tcp_check_req(struct sock *sk, struct sk_buff *skb,
 		tcp_parse_options(sock_net(sk), skb, &tmp_opt, 0, NULL);
 
 		if (tmp_opt.saw_tstamp) {
-			tmp_opt.ts_recent = READ_ONCE(req->ts_recent);
+			tmp_opt.ts_recent = req->ts_recent;
 			if (tmp_opt.rcv_tsecr) {
 				if (inet_rsk(req)->tstamp_ok && !fastopen)
 					tsecr_reject = !between(tmp_opt.rcv_tsecr,

net/ipv4/tcp_output.c

@@ -949,7 +949,7 @@ static unsigned int tcp_synack_options(const struct sock *sk,
 			tcp_rsk(req)->snt_tsval_first = opts->tsval;
 		}
 		WRITE_ONCE(tcp_rsk(req)->snt_tsval_last, opts->tsval);
-		opts->tsecr = READ_ONCE(req->ts_recent);
+		opts->tsecr = req->ts_recent;
 		remaining -= TCPOLEN_TSTAMP_ALIGNED;
 	}
 	if (likely(ireq->sack_ok)) {

net/ipv6/tcp_ipv6.c

@@ -1279,7 +1279,7 @@ static void tcp_v6_reqsk_send_ack(const struct sock *sk, struct sk_buff *skb,
 			tcp_rsk(req)->rcv_nxt,
 			tcp_synack_window(req) >> inet_rsk(req)->rcv_wscale,
 			tcp_rsk_tsval(tcp_rsk(req)),
-			READ_ONCE(req->ts_recent), sk->sk_bound_dev_if,
+			req->ts_recent, sk->sk_bound_dev_if,
 			&key, ipv6_get_dsfield(ipv6_hdr(skb)), 0,
 			READ_ONCE(sk->sk_priority),
 			READ_ONCE(tcp_rsk(req)->txhash));