netdev - [PATCH 2/2] net: tcp: Add noinline_for_tracing annotation for tcp_drop

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Message-Id: <20241024093742.87681-3-laoar.shao@gmail.com>
Date: Thu, 24 Oct 2024 17:37:42 +0800
From: Yafang Shao <laoar.shao@...il.com>
To: edumazet@...gle.com,
	davem@...emloft.net,
	dsahern@...nel.org,
	kuba@...nel.org,
	pabeni@...hat.com
Cc: netdev@...r.kernel.org,
	Yafang Shao <laoar.shao@...il.com>,
	Menglong Dong <menglong8.dong@...il.com>
Subject: [PATCH 2/2] net: tcp: Add noinline_for_tracing annotation for tcp_drop_reason()

We previously hooked the tcp_drop_reason() function using BPF to monitor
TCP drop reasons. However, after upgrading our compiler from GCC 9 to GCC
11, tcp_drop_reason() is now inlined, preventing us from hooking into it.
To address this, it would be beneficial to make noinline explicitly for
tracing.

Link: https://lore.kernel.org/netdev/CANn89iJuShCmidCi_ZkYABtmscwbVjhuDta1MS5LxV_4H9tKOA@mail.gmail.com/
Suggested-by: Eric Dumazet <edumazet@...gle.com>
Signed-off-by: Yafang Shao <laoar.shao@...il.com>
Cc: Menglong Dong <menglong8.dong@...il.com>
---
 net/ipv4/tcp_input.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
index cc05ec1faac8..cf1e2e3a7407 100644
--- a/net/ipv4/tcp_input.c
+++ b/net/ipv4/tcp_input.c
@@ -4894,8 +4894,8 @@ static bool tcp_ooo_try_coalesce(struct sock *sk,
 	return res;
 }
 
-static void tcp_drop_reason(struct sock *sk, struct sk_buff *skb,
-			    enum skb_drop_reason reason)
+noinline_for_tracing static void
+tcp_drop_reason(struct sock *sk, struct sk_buff *skb, enum skb_drop_reason reason)
 {
 	sk_drops_add(sk, skb);
 	sk_skb_reason_drop(sk, skb, reason);
-- 
2.43.5