6.6-stable review patch. If anyone has any objections, please let me know.
------------------
From: Eric Dumazet <edumazet@xxxxxxxxxx>
[ Upstream commit a562c0a2d651e040681b0bfce9b4d229ac3b0b8c ]
Busy polling while holding the socket lock makes litle sense,
because incoming packets wont reach our receive queue.
Fixes: 8465a5fcd1ce ("sctp: add support for busy polling to sctp protocol")
Reported-by: Jacob Moroni <jmoroni@xxxxxxxxxx>
Signed-off-by: Eric Dumazet <edumazet@xxxxxxxxxx>
Cc: Marcelo Ricardo Leitner <marcelo.leitner@xxxxxxxxx>
Cc: Xin Long <lucien.xin@xxxxxxxxx>
Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
net/sctp/socket.c | 10 ++++------
1 file changed, 4 insertions(+), 6 deletions(-)
diff --git a/net/sctp/socket.c b/net/sctp/socket.c
index 5fb02bbb4b34..6b9fcdb0952a 100644
--- a/net/sctp/socket.c
+++ b/net/sctp/socket.c
@@ -2102,6 +2102,10 @@ static int sctp_recvmsg(struct sock *sk, struct msghdr *msg, size_t len,
if (unlikely(flags & MSG_ERRQUEUE))
return inet_recv_error(sk, msg, len, addr_len);
+ if (sk_can_busy_loop(sk) &&
+ skb_queue_empty_lockless(&sk->sk_receive_queue))
+ sk_busy_loop(sk, flags & MSG_DONTWAIT);
+
lock_sock(sk);
if (sctp_style(sk, TCP) && !sctp_sstate(sk, ESTABLISHED) &&
@@ -9046,12 +9050,6 @@ struct sk_buff *sctp_skb_recv_datagram(struct sock *sk, int flags, int *err)
if (sk->sk_shutdown & RCV_SHUTDOWN)
break;
- if (sk_can_busy_loop(sk)) {
- sk_busy_loop(sk, flags & MSG_DONTWAIT);
-
- if (!skb_queue_empty_lockless(&sk->sk_receive_queue))
- continue;
- }
/* User doesn't want to wait. */
error = -EAGAIN;
--
2.43.0
