netdev - [PATCH net-next] net: sock_dequeue_err

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Date: Thu,  5 Oct 2023 11:45:04 +0000
From: Eric Dumazet <edumazet@...gle.com>
To: "David S . Miller" <davem@...emloft.net>, Jakub Kicinski <kuba@...nel.org>, 
	Paolo Abeni <pabeni@...hat.com>
Cc: netdev@...r.kernel.org, eric.dumazet@...il.com, 
	Eric Dumazet <edumazet@...gle.com>
Subject: [PATCH net-next] 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@...gle.com>
---
 net/core/skbuff.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/net/core/skbuff.c b/net/core/skbuff.c
index da3f96bdd6f66cbea2f8e17513bff05a036a48ac..0401f40973a584ba4a89509b02510c8352bd6fb5 100644
--- 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))) {
-- 
2.42.0.582.g8ccd20d70d-goog