linux-kernel - [PATCH 5.12 024/178] net: lantiq: disable interrupt before sheduling NAPI

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Message-Id: <20210621154922.638428677@linuxfoundation.org>
Date:   Mon, 21 Jun 2021 18:13:58 +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, Aleksander Jan Bajkowski <olek2@...pl>,
        Hauke Mehrtens <hauke@...ke-m.de>,
        "David S. Miller" <davem@...emloft.net>,
        Sasha Levin <sashal@...nel.org>
Subject: [PATCH 5.12 024/178] net: lantiq: disable interrupt before sheduling NAPI

From: Aleksander Jan Bajkowski <olek2@...pl>

[ Upstream commit f2386cf7c5f4ff5d7b584f5d92014edd7df6c676 ]

This patch fixes TX hangs with threaded NAPI enabled. The scheduled
NAPI seems to be executed in parallel with the interrupt on second
thread. Sometimes it happens that ltq_dma_disable_irq() is executed
after xrx200_tx_housekeeping(). The symptom is that TX interrupts
are disabled in the DMA controller. As a result, the TX hangs after
a few seconds of the iperf test. Scheduling NAPI after disabling
interrupts fixes this issue.

Tested on Lantiq xRX200 (BT Home Hub 5A).

Fixes: 9423361da523 ("net: lantiq: Disable IRQs only if NAPI gets scheduled ")
Signed-off-by: Aleksander Jan Bajkowski <olek2@...pl>
Acked-by: Hauke Mehrtens <hauke@...ke-m.de>
Signed-off-by: David S. Miller <davem@...emloft.net>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 drivers/net/ethernet/lantiq_xrx200.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/net/ethernet/lantiq_xrx200.c b/drivers/net/ethernet/lantiq_xrx200.c
index 135ba5b6ae98..3da494df72f3 100644
--- a/drivers/net/ethernet/lantiq_xrx200.c
+++ b/drivers/net/ethernet/lantiq_xrx200.c
@@ -352,8 +352,8 @@ static irqreturn_t xrx200_dma_irq(int irq, void *ptr)
 	struct xrx200_chan *ch = ptr;
 
 	if (napi_schedule_prep(&ch->napi)) {
-		__napi_schedule(&ch->napi);
 		ltq_dma_disable_irq(&ch->dma);
+		__napi_schedule(&ch->napi);
 	}
 
 	ltq_dma_ack_irq(&ch->dma);
-- 
2.30.2