[PATCH AUTOSEL 4.14 52/61] nfp: avoid soft lockups under control message storm

[Sasha Levin <sashal@kernel.org>]

From: Jakub Kicinski <jakub.kicinski@netronome.com>

[ Upstream commit ff58e2df62ce29d0552278c290ae494b30fe0c6f ]

When FW floods the driver with control messages try to exit the cmsg
processing loop every now and then to avoid soft lockups.  Cmsg
processing is generally very lightweight so 512 seems like a reasonable
budget, which should not be exceeded under normal conditions.

Fixes: 77ece8d5f196 ("nfp: add control vNIC datapath")
Signed-off-by: Jakub Kicinski <jakub.kicinski@netronome.com>
Reviewed-by: Simon Horman <simon.horman@netronome.com>
Tested-by: Pieter Jansen van Vuuren <pieter.jansenvanvuuren@netronome.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 .../net/ethernet/netronome/nfp/nfp_net_common.c | 17 ++++++++++++-----
 1 file changed, 12 insertions(+), 5 deletions(-)

diff --git a/drivers/net/ethernet/netronome/nfp/nfp_net_common.c b/drivers/net/ethernet/netronome/nfp/nfp_net_common.c
index 56751990bcee..6df2c8b2ce6f 100644
--- a/drivers/net/ethernet/netronome/nfp/nfp_net_common.c
+++ b/drivers/net/ethernet/netronome/nfp/nfp_net_common.c
@@ -2058,14 +2058,17 @@ nfp_ctrl_rx_one(struct nfp_net *nn, struct nfp_net_dp *dp,
 	return true;
 }
 
-static void nfp_ctrl_rx(struct nfp_net_r_vector *r_vec)
+static bool nfp_ctrl_rx(struct nfp_net_r_vector *r_vec)
 {
 	struct nfp_net_rx_ring *rx_ring = r_vec->rx_ring;
 	struct nfp_net *nn = r_vec->nfp_net;
 	struct nfp_net_dp *dp = &nn->dp;
+	unsigned int budget = 512;
 
-	while (nfp_ctrl_rx_one(nn, dp, r_vec, rx_ring))
+	while (nfp_ctrl_rx_one(nn, dp, r_vec, rx_ring) && budget--)
 		continue;
+
+	return budget;
 }
 
 static void nfp_ctrl_poll(unsigned long arg)
@@ -2077,9 +2080,13 @@ static void nfp_ctrl_poll(unsigned long arg)
 	__nfp_ctrl_tx_queued(r_vec);
 	spin_unlock_bh(&r_vec->lock);
 
-	nfp_ctrl_rx(r_vec);
-
-	nfp_net_irq_unmask(r_vec->nfp_net, r_vec->irq_entry);
+	if (nfp_ctrl_rx(r_vec)) {
+		nfp_net_irq_unmask(r_vec->nfp_net, r_vec->irq_entry);
+	} else {
+		tasklet_schedule(&r_vec->tasklet);
+		nn_dp_warn(&r_vec->nfp_net->dp,
+			   "control message budget exceeded!\n");
+	}
 }
 
 /* Setup and Configuration
-- 
2.17.1