From ee2aabd3fc2eef4c1a0ebdadccc76fbff74b94fc Mon Sep 17 00:00:00 2001 From: Eric Dumazet Date: Thu, 12 Dec 2019 12:55:30 -0800 Subject: tcp: refine tcp_write_queue_empty() implementation Due to how tcp_sendmsg() is implemented, we can have an empty skb at the tail of the write queue. Most [1] tcp_write_queue_empty() callers want to know if there is anything to send (payload and/or FIN) Instead of checking if the sk_write_queue is empty, we need to test if tp->write_seq == tp->snd_nxt [1] tcp_send_fin() was the only caller that expected to see if an skb was in the write queue, I have changed the code to reuse the tcp_write_queue_tail() result. Signed-off-by: Eric Dumazet Cc: Neal Cardwell Acked-by: Soheil Hassas Yeganeh Signed-off-by: Jakub Kicinski --- include/net/tcp.h | 11 ++++++++++- 1 file changed, 10 insertions(+), 1 deletion(-) (limited to 'include/net/tcp.h') diff --git a/include/net/tcp.h b/include/net/tcp.h index 86b9a8766648..e460ea7f767b 100644 --- a/include/net/tcp.h +++ b/include/net/tcp.h @@ -1766,9 +1766,18 @@ static inline bool tcp_skb_is_last(const struct sock *sk, return skb_queue_is_last(&sk->sk_write_queue, skb); } +/** + * tcp_write_queue_empty - test if any payload (or FIN) is available in write queue + * @sk: socket + * + * Since the write queue can have a temporary empty skb in it, + * we must not use "return skb_queue_empty(&sk->sk_write_queue)" + */ static inline bool tcp_write_queue_empty(const struct sock *sk) { - return skb_queue_empty(&sk->sk_write_queue); + const struct tcp_sock *tp = tcp_sk(sk); + + return tp->write_seq == tp->snd_nxt; } static inline bool tcp_rtx_queue_empty(const struct sock *sk) -- cgit v1.2.3-59-g8ed1b