linux-kernel - [PATCH 5.12 037/178] Revert "net/mlx5: Arm only EQs with EQEs"

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Message-Id: <20210621154923.331869102@linuxfoundation.org>
Date:   Mon, 21 Jun 2021 18:14:11 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Shay Drory <shayd@...dia.com>,
        Parav Pandit <parav@...dia.com>,
        Saeed Mahameed <saeedm@...dia.com>,
        Sasha Levin <sashal@...nel.org>
Subject: [PATCH 5.12 037/178] Revert "net/mlx5: Arm only EQs with EQEs"

From: Shay Drory <shayd@...dia.com>

[ Upstream commit 7a545077cb6701957e84c7f158630bb5c984e648 ]

In the scenario described below, an EQ can remain in FIRED state which
can result in missing an interrupt generation.

The scenario:

device                       mlx5_core driver
------                       ----------------
EQ1.eqe generated
EQ1.MSI-X sent
EQ1.state = FIRED
EQ2.eqe generated
                             mlx5_irq()
                               polls - eq1_eqes()
                               arm eq1
                               polls - eq2_eqes()
                               arm eq2
EQ2.MSI-X sent
EQ2.state = FIRED
                              mlx5_irq()
                              polls - eq2_eqes() -- no eqes found
                              driver skips EQ arming;

->EQ2 remains fired, misses generating interrupt.

Hence, always arm the EQ by reverting the cited commit in fixes tag.

Fixes: d894892dda25 ("net/mlx5: Arm only EQs with EQEs")
Signed-off-by: Shay Drory <shayd@...dia.com>
Reviewed-by: Parav Pandit <parav@...dia.com>
Signed-off-by: Saeed Mahameed <saeedm@...dia.com>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 drivers/net/ethernet/mellanox/mlx5/core/eq.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/drivers/net/ethernet/mellanox/mlx5/core/eq.c b/drivers/net/ethernet/mellanox/mlx5/core/eq.c
index 1fa9c18563da..31c6a3b91f4a 100644
--- a/drivers/net/ethernet/mellanox/mlx5/core/eq.c
+++ b/drivers/net/ethernet/mellanox/mlx5/core/eq.c
@@ -136,7 +136,7 @@ static int mlx5_eq_comp_int(struct notifier_block *nb,
 
 	eqe = next_eqe_sw(eq);
 	if (!eqe)
-		return 0;
+		goto out;
 
 	do {
 		struct mlx5_core_cq *cq;
@@ -161,6 +161,8 @@ static int mlx5_eq_comp_int(struct notifier_block *nb,
 		++eq->cons_index;
 
 	} while ((++num_eqes < MLX5_EQ_POLLING_BUDGET) && (eqe = next_eqe_sw(eq)));
+
+out:
 	eq_update_ci(eq, 1);
 
 	if (cqn != -1)
@@ -248,9 +250,9 @@ static int mlx5_eq_async_int(struct notifier_block *nb,
 		++eq->cons_index;
 
 	} while ((++num_eqes < MLX5_EQ_POLLING_BUDGET) && (eqe = next_eqe_sw(eq)));
-	eq_update_ci(eq, 1);
 
 out:
+	eq_update_ci(eq, 1);
 	mlx5_eq_async_int_unlock(eq_async, recovery, &flags);
 
 	return unlikely(recovery) ? num_eqes : 0;
-- 
2.30.2