| From foo@baz Wed 06 Nov 2019 04:08:37 PM CET |
| From: Eric Dumazet <edumazet@google.com> |
| Date: Wed, 23 Oct 2019 22:44:51 -0700 |
| Subject: net: use skb_queue_empty_lockless() in busy poll contexts |
| |
| 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; |
| } |
| |