[PATCH 5.7 014/244] tcp: fix SO_RCVLOWAT possible hangs under high mem pressure

[Greg Kroah-Hartman]

From: Eric Dumazet <eduma...@google.com>

[ Upstream commit ba3bb0e76ccd464bb66665a1941fabe55dadb3ba ]

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 <eduma...@google.com>
Signed-off-by: David S. Miller <da...@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gre...@linuxfoundation.org>
---
 net/ipv4/tcp_input.c |    2 ++
 1 file changed, 2 insertions(+)

--- a/net/ipv4/tcp_input.c
+++ b/net/ipv4/tcp_input.c
@@ -4570,6 +4570,7 @@ static void tcp_data_queue_ofo(struct so
 
        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;
        }
@@ -4816,6 +4817,7 @@ 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;
                }