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 <edumazet@google.com>
Acked-by: Soheil Hassas Yeganeh <soheil@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c
index b945c2b..5c7ed14 100644
--- a/net/ipv4/tcp.c
+++ b/net/ipv4/tcp.c
@@ -1084,6 +1084,7 @@
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 @@
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 @@
if (!skb)
goto wait_for_memory;
+ process_backlog = true;
/*
* Check whether we can use HW checksum.
*/