net: use skb_queue_empty_lockless() in busy poll contexts

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>

4 files changed, 4 insertions, 4 deletions

diff --git a/net/core/datagram.c b/net/core/datagram.c
index 5b685e110aff..03515e46a49a 100644
--- a/net/core/datagram.c
+++ b/net/core/datagram.c
@@ -278,7 +278,7 @@ struct sk_buff *__skb_try_recv_datagram(struct sock *sk, unsigned int flags,
                         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;
 
diff --git a/net/core/sock.c b/net/core/sock.c
index a515392ba84b..b8e758bcb6ad 100644
--- a/net/core/sock.c
+++ b/net/core/sock.c
@@ -3600,7 +3600,7 @@ bool sk_busy_loop_end(void *p, unsigned long start_time)
 {
         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);
diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c
index ffef502f5292..d8876f0e9672 100644
--- a/net/ipv4/tcp.c
+++ b/net/ipv4/tcp.c
@@ -1964,7 +1964,7 @@ int tcp_recvmsg(struct sock *sk, struct msghdr *msg, size_t len, int nonblock,
         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);
 
diff --git a/net/sctp/socket.c b/net/sctp/socket.c
index cfb25391b8b0..ca81e06df165 100644
--- a/net/sctp/socket.c
+++ b/net/sctp/socket.c
@@ -8871,7 +8871,7 @@ struct sk_buff *sctp_skb_recv_datagram(struct sock *sk, int flags,
                 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;
                 }