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>

diff --git a/drivers/crypto/chelsio/chtls/chtls_io.c b/drivers/crypto/chelsio/chtls/chtls_io.c
index 0891ab8..98bc5a4 100644 (file)
--- a/drivers/crypto/chelsio/chtls/chtls_io.c
+++ b/drivers/crypto/chelsio/chtls/chtls_io.c
@@ -1702,7 +1702,7 @@ int chtls_recvmsg(struct sock *sk, struct msghdr *msg, size_t len,
                return peekmsg(sk, msg, len, nonblock, flags);
 
        if (sk_can_busy_loop(sk) &&
-           skb_queue_empty(&sk->sk_receive_queue) &&
+           skb_queue_empty_lockless(&sk->sk_receive_queue) &&
            sk->sk_state == TCP_ESTABLISHED)
                sk_busy_loop(sk, nonblock);
 

diff --git a/drivers/nvme/host/tcp.c b/drivers/nvme/host/tcp.c
index 770dbcb..7544be8 100644 (file)
--- a/drivers/nvme/host/tcp.c
+++ b/drivers/nvme/host/tcp.c
@@ -2219,7 +2219,7 @@ static int nvme_tcp_poll(struct blk_mq_hw_ctx *hctx)
        struct nvme_tcp_queue *queue = hctx->driver_data;
        struct sock *sk = queue->sock->sk;
 
-       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_busy_loop(sk, true);
        nvme_tcp_try_recv(queue);
        return queue->nr_cqe;

diff --git a/net/core/datagram.c b/net/core/datagram.c
index 5b685e1..03515e4 100644 (file)
--- 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 a515392..b8e758b 100644 (file)
--- 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 ffef502..d8876f0 100644 (file)
--- 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 cfb2539..ca81e06 100644 (file)
--- 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;
                }