From d4011239f46ac6e407af61e3f74d1e3874fc9394 Mon Sep 17 00:00:00 2001 From: Eric Dumazet Date: Mon, 2 May 2016 21:49:25 -0700 Subject: [PATCH] tcp: guarantee forward progress in tcp_sendmsg() Under high rx pressure, it is possible tcp_sendmsg() never has a chance to allocate an skb and loop forever as sk_flush_backlog() would always return true. Fix this by calling sk_flush_backlog() only if one skb had been allocated and filled before last backlog check. Fixes: d41a69f1d390 ("tcp: make tcp_sendmsg() aware of socket backlog") Signed-off-by: Eric Dumazet Acked-by: Soheil Hassas Yeganeh Signed-off-by: David S. Miller --- net/ipv4/tcp.c | 7 +++++-- 1 file changed, 5 insertions(+), 2 deletions(-) diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c index b945c2b046c5..5c7ed147449c 100644 --- a/net/ipv4/tcp.c +++ b/net/ipv4/tcp.c @@ -1084,6 +1084,7 @@ int tcp_sendmsg(struct sock *sk, struct msghdr *msg, size_t size) struct sockcm_cookie sockc; int flags, err, copied = 0; int mss_now = 0, size_goal, copied_syn = 0; + bool process_backlog = false; bool sg; long timeo; @@ -1167,9 +1168,10 @@ new_segment: if (!sk_stream_memory_free(sk)) goto wait_for_sndbuf; - if (sk_flush_backlog(sk)) + if (process_backlog && sk_flush_backlog(sk)) { + process_backlog = false; goto restart; - + } skb = sk_stream_alloc_skb(sk, select_size(sk, sg), sk->sk_allocation, @@ -1177,6 +1179,7 @@ new_segment: if (!skb) goto wait_for_memory; + process_backlog = true; /* * Check whether we can use HW checksum. */ -- 2.20.1