diff --git a/include/net/tcp.h b/include/net/tcp.h
index 364426a2be5a..309801f7eb82 100644
--- a/include/net/tcp.h
+++ b/include/net/tcp.h
@@ -1165,6 +1165,19 @@ static inline void tcp_sack_reset(struct tcp_options_received *rx_opt)
 }
 
 u32 tcp_default_init_rwnd(u32 mss);
+void tcp_cwnd_restart(struct sock *sk, s32 delta);
+
+static inline void tcp_slow_start_after_idle_check(struct sock *sk)
+{
+	struct tcp_sock *tp = tcp_sk(sk);
+	s32 delta;
+
+	if (!sysctl_tcp_slow_start_after_idle || tp->packets_out)
+		return;
+	delta = tcp_time_stamp - tp->lsndtime;
+	if (delta > inet_csk(sk)->icsk_rto)
+		tcp_cwnd_restart(sk, delta);
+}
 
 /* Determine a window scaling and initial window to offer. */
 void tcp_select_initial_window(int __space, __u32 mss, __u32 *rcv_wnd,
diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c
index 45534a5ab430..b8b8fa184f75 100644
--- a/net/ipv4/tcp.c
+++ b/net/ipv4/tcp.c
@@ -627,6 +627,8 @@ static void skb_entail(struct sock *sk, struct sk_buff *skb)
 	sk_mem_charge(sk, skb->truesize);
 	if (tp->nonagle & TCP_NAGLE_PUSH)
 		tp->nonagle &= ~TCP_NAGLE_PUSH;
+
+	tcp_slow_start_after_idle_check(sk);
 }
 
 static inline void tcp_mark_urg(struct tcp_sock *tp, int flags)
diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
index 4e4d6bcd0ca9..0abca2841de2 100644
--- a/net/ipv4/tcp_input.c
+++ b/net/ipv4/tcp_input.c
@@ -3332,6 +3332,9 @@ static int tcp_ack_update_window(struct sock *sk, const struct sk_buff *skb, u32
 			tp->pred_flags = 0;
 			tcp_fast_path_check(sk);
 
+			if (tcp_send_head(sk))
+				tcp_slow_start_after_idle_check(sk);
+
 			if (nwin > tp->max_window) {
 				tp->max_window = nwin;
 				tcp_sync_mss(sk, inet_csk(sk)->icsk_pmtu_cookie);
diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c
index 444ab5beecbd..1188e4fcf23b 100644
--- a/net/ipv4/tcp_output.c
+++ b/net/ipv4/tcp_output.c
@@ -137,12 +137,12 @@ static __u16 tcp_advertise_mss(struct sock *sk)
 }
 
 /* RFC2861. Reset CWND after idle period longer RTO to "restart window".
- * This is the first part of cwnd validation mechanism. */
-static void tcp_cwnd_restart(struct sock *sk, const struct dst_entry *dst)
+ * This is the first part of cwnd validation mechanism.
+ */
+void tcp_cwnd_restart(struct sock *sk, s32 delta)
 {
 	struct tcp_sock *tp = tcp_sk(sk);
-	s32 delta = tcp_time_stamp - tp->lsndtime;
-	u32 restart_cwnd = tcp_init_cwnd(tp, dst);
+	u32 restart_cwnd = tcp_init_cwnd(tp, __sk_dst_get(sk));
 	u32 cwnd = tp->snd_cwnd;
 
 	tcp_ca_event(sk, CA_EVENT_CWND_RESTART);
@@ -164,10 +164,6 @@ static void tcp_event_data_sent(struct tcp_sock *tp,
 	struct inet_connection_sock *icsk = inet_csk(sk);
 	const u32 now = tcp_time_stamp;
 
-	if (sysctl_tcp_slow_start_after_idle &&
-	    (!tp->packets_out && (s32)(now - tp->lsndtime) > icsk->icsk_rto))
-		tcp_cwnd_restart(sk, __sk_dst_get(sk));
-
 	tp->lsndtime = now;
 
 	/* If it is a reply for ato after last received