From: Eric Dumazet edumazet@google.com
[ Upstream commit 3f926af3f4d688e2e11e7f8ed04e277a14d4d4a4 ]
Busy polling usually runs without locks. Let's use skb_queue_empty_lockless() instead of skb_queue_empty()
Also uses READ_ONCE() in __skb_try_recv_datagram() to address a similar potential problem.
Signed-off-by: Eric Dumazet edumazet@google.com Signed-off-by: David S. Miller davem@davemloft.net Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- net/core/datagram.c | 2 +- net/core/sock.c | 2 +- net/ipv4/tcp.c | 2 +- net/sctp/socket.c | 2 +- 4 files changed, 4 insertions(+), 4 deletions(-)
--- a/net/core/datagram.c +++ b/net/core/datagram.c @@ -281,7 +281,7 @@ struct sk_buff *__skb_try_recv_datagram( break;
sk_busy_loop(sk, flags & MSG_DONTWAIT); - } while (sk->sk_receive_queue.prev != *last); + } while (READ_ONCE(sk->sk_receive_queue.prev) != *last);
error = -EAGAIN;
--- a/net/core/sock.c +++ b/net/core/sock.c @@ -3381,7 +3381,7 @@ bool sk_busy_loop_end(void *p, unsigned { struct sock *sk = p;
- return !skb_queue_empty(&sk->sk_receive_queue) || + return !skb_queue_empty_lockless(&sk->sk_receive_queue) || sk_busy_loop_timeout(sk, start_time); } EXPORT_SYMBOL(sk_busy_loop_end); --- a/net/ipv4/tcp.c +++ b/net/ipv4/tcp.c @@ -1787,7 +1787,7 @@ int tcp_recvmsg(struct sock *sk, struct if (unlikely(flags & MSG_ERRQUEUE)) return inet_recv_error(sk, msg, len, addr_len);
- if (sk_can_busy_loop(sk) && skb_queue_empty(&sk->sk_receive_queue) && + if (sk_can_busy_loop(sk) && skb_queue_empty_lockless(&sk->sk_receive_queue) && (sk->sk_state == TCP_ESTABLISHED)) sk_busy_loop(sk, nonblock);
--- a/net/sctp/socket.c +++ b/net/sctp/socket.c @@ -7716,7 +7716,7 @@ struct sk_buff *sctp_skb_recv_datagram(s if (sk_can_busy_loop(sk)) { sk_busy_loop(sk, noblock);
- if (!skb_queue_empty(&sk->sk_receive_queue)) + if (!skb_queue_empty_lockless(&sk->sk_receive_queue)) continue; }