netdev - [net 16/16] mlx5e: add add missing BH locking around napi

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Message-Id: <20210519060523.17875-17-saeed@kernel.org>
Date:   Tue, 18 May 2021 23:05:23 -0700
From:   Saeed Mahameed <saeed@...nel.org>
To:     "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>
Cc:     netdev@...r.kernel.org, Tariq Toukan <tariqt@...dia.com>,
        Leon Romanovsky <leonro@...dia.com>,
        Saeed Mahameed <saeedm@...dia.com>
Subject: [net 16/16] mlx5e: add add missing BH locking around napi_schdule()

From: Jakub Kicinski <kuba@...nel.org>

It's not correct to call napi_schedule() in pure process
context. Because we use __raise_softirq_irqoff() we require
callers to be in a context which will eventually lead to
softirq handling (hardirq, bh disabled, etc.).

With code as is users will see:

 NOHZ tick-stop error: Non-RCU local softirq work is pending, handler #08!!!

Fixes: a8dd7ac12fc3 ("net/mlx5e: Generalize RQ activation")
Signed-off-by: Jakub Kicinski <kuba@...nel.org>
Signed-off-by: Saeed Mahameed <saeedm@...dia.com>
---
 drivers/net/ethernet/mellanox/mlx5/core/en_main.c | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/drivers/net/ethernet/mellanox/mlx5/core/en_main.c b/drivers/net/ethernet/mellanox/mlx5/core/en_main.c
index d1b9a4040d60..ad0f69480b9c 100644
--- a/drivers/net/ethernet/mellanox/mlx5/core/en_main.c
+++ b/drivers/net/ethernet/mellanox/mlx5/core/en_main.c
@@ -889,10 +889,13 @@ int mlx5e_open_rq(struct mlx5e_params *params, struct mlx5e_rq_param *param,
 void mlx5e_activate_rq(struct mlx5e_rq *rq)
 {
 	set_bit(MLX5E_RQ_STATE_ENABLED, &rq->state);
-	if (rq->icosq)
+	if (rq->icosq) {
 		mlx5e_trigger_irq(rq->icosq);
-	else
+	} else {
+		local_bh_disable();
 		napi_schedule(rq->cq.napi);
+		local_bh_enable();
+	}
 }
 
 void mlx5e_deactivate_rq(struct mlx5e_rq *rq)
-- 
2.31.1