net: sock_dequeue_err_skb() optimization

Exit early if the list is empty.

Some applications using TCP zerocopy are calling
recvmsg( ... MSG_ERRQUEUE) and hit this case quite often,
probably because busy polling only deals with sk_receive_queue.

Signed-off-by: Eric Dumazet <edumazet@google.com>
Link: https://lore.kernel.org/r/20231005114504.642589-1-edumazet@google.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

diff --git a/net/core/skbuff.c b/net/core/skbuff.c
index da3f96bdd6f66cbea2f8e17513bff05a036a48ac..0401f40973a584ba4a89509b02510c8352bd6fb5 100644 (file)
--- a/net/core/skbuff.c
+++ b/net/core/skbuff.c
@@ -5162,6 +5162,9 @@ struct sk_buff *sock_dequeue_err_skb(struct sock *sk)
        bool icmp_next = false;
        unsigned long flags;
 
+       if (skb_queue_empty_lockless(q))
+               return NULL;
+
        spin_lock_irqsave(&q->lock, flags);
        skb = __skb_dequeue(q);
        if (skb && (skb_next = skb_peek(q))) {