tcp: fix SO_RCVLOWAT possible hangs under high mem pressure

Whenever tcp_try_rmem_schedule() returns an error, we are under
trouble and should make sure to wakeup readers so that they
can drain socket queues and eventually make room.

Fixes: 03f45c883c6f ("tcp: avoid extra wakeups for SO_RCVLOWAT users")
Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
index f3a0eb1..9615e72 100644 (file)
--- a/net/ipv4/tcp_input.c
+++ b/net/ipv4/tcp_input.c
@@ -4582,6 +4582,7 @@ static void tcp_data_queue_ofo(struct sock *sk, struct sk_buff *skb)
 
        if (unlikely(tcp_try_rmem_schedule(sk, skb, skb->truesize))) {
                NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPOFODROP);
+               sk->sk_data_ready(sk);
                tcp_drop(sk, skb);
                return;
        }
@@ -4828,6 +4829,7 @@ queue_and_out:
                        sk_forced_mem_schedule(sk, skb->truesize);
                else if (tcp_try_rmem_schedule(sk, skb, skb->truesize)) {
                        NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPRCVQDROP);
+                       sk->sk_data_ready(sk);
                        goto drop;
                }