This is a note to let you know that I've just added the patch titled
sctp: fix busy polling
to the 6.6-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
sctp-fix-busy-polling.patch
and it can be found in the queue-6.6 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
commit 495d5a7438b878810f501002758d57f21921922b
Author: Eric Dumazet <edumazet@xxxxxxxxxx>
Date: Tue Dec 19 17:00:17 2023 +0000
sctp: fix busy polling
[ 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>
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;
