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Subject[PATCH 4.19 57/79] net: use skb_queue_empty_lockless() in busy poll contexts
Date
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>
---
drivers/crypto/chelsio/chtls/chtls_io.c | 2 +-
net/core/datagram.c | 2 +-
net/core/sock.c | 2 +-
net/ipv4/tcp.c | 2 +-
net/sctp/socket.c | 2 +-
5 files changed, 5 insertions(+), 5 deletions(-)

--- a/drivers/crypto/chelsio/chtls/chtls_io.c
+++ b/drivers/crypto/chelsio/chtls/chtls_io.c
@@ -1716,7 +1716,7 @@ int chtls_recvmsg(struct sock *sk, struc
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);

--- a/net/core/datagram.c
+++ b/net/core/datagram.c
@@ -279,7 +279,7 @@ 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
@@ -3483,7 +3483,7 @@ 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
@@ -1948,7 +1948,7 @@ 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
@@ -8334,7 +8334,7 @@ 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;
}


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