netdev - [PATCH v1 5/5] idpf: warn on possible ctlq overflow

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Message-ID: <20240813182747.1770032-6-manojvishy@google.com>
Date: Tue, 13 Aug 2024 18:27:47 +0000
From: Manoj Vishwanathan <manojvishy@...gle.com>
To: Tony Nguyen <anthony.l.nguyen@...el.com>, 
	Przemek Kitszel <przemyslaw.kitszel@...el.com>, "David S. Miller" <davem@...emloft.net>, 
	Eric Dumazet <edumazet@...gle.com>, intel-wired-lan@...ts.osuosl.org
Cc: netdev@...r.kernel.org, linux-kernel@...r.kernel.org, 
	google-lan-reviews@...glegroups.com, Willem de Bruijn <willemb@...gle.com>, 
	Manoj Vishwanathan <manojvishy@...gle.com>
Subject: [PATCH v1 5/5] idpf: warn on possible ctlq overflow

From: Willem de Bruijn <willemb@...gle.com>

The virtchannel control queue is lossy to avoid deadlock. Ensure that
no losses occur in practice. Detect a full queue, when overflows may
have happened.

In practice, virtchnl is synchronous currenty and messages generally
take a single slot. Using up anywhere near the full ring is not
expected.

Tested: Running several traffic tests and no logs seen in the dmesg

Signed-off-by: Willem de Bruijn <willemb@...gle.com>
Signed-off-by: Manoj Vishwanathan <manojvishy@...gle.com>
---
 drivers/net/ethernet/intel/idpf/idpf_virtchnl.c | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/drivers/net/ethernet/intel/idpf/idpf_virtchnl.c b/drivers/net/ethernet/intel/idpf/idpf_virtchnl.c
index 07239afb285e..1852836d81e4 100644
--- a/drivers/net/ethernet/intel/idpf/idpf_virtchnl.c
+++ b/drivers/net/ethernet/intel/idpf/idpf_virtchnl.c
@@ -218,6 +218,15 @@ static int idpf_mb_clean(struct idpf_adapter *adapter)
 	if (err)
 		goto err_kfree;
 
+	/* Warn if messages may have been dropped */
+	if (num_q_msg == IDPF_DFLT_MBX_Q_LEN) {
+		static atomic_t mbx_full = ATOMIC_INIT(0);
+		int cnt;
+
+		cnt = atomic_inc_return(&mbx_full);
+		net_warn_ratelimited("%s: ctlq full (%d)\n", __func__, cnt);
+	}
+
 	for (i = 0; i < num_q_msg; i++) {
 		if (!q_msg[i])
 			continue;
-- 
2.46.0.76.ge559c4bf1a-goog