linux-kernel - [PATCH 4.19 030/120] net: stmmac: fix watchdog timeout during suspend/resume stress test

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Date:   Mon, 15 Mar 2021 14:56:21 +0100
From:   gregkh@...uxfoundation.org
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Joakim Zhang <qiangqing.zhang@....com>,
        Jakub Kicinski <kuba@...nel.org>
Subject: [PATCH 4.19 030/120] net: stmmac: fix watchdog timeout during suspend/resume stress test

From: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

From: Joakim Zhang <qiangqing.zhang@....com>

commit c511819d138de38e1637eedb645c207e09680d0f upstream.

stmmac_xmit() call stmmac_tx_timer_arm() at the end to modify tx timer to
do the transmission cleanup work. Imagine such a situation, stmmac enters
suspend immediately after tx timer modified, it's expire callback
stmmac_tx_clean() would not be invoked. This could affect BQL, since
netdev_tx_sent_queue() has been called, but netdev_tx_completed_queue()
have not been involved, as a result, dql_avail(&dev_queue->dql) finally
always return a negative value.

__dev_queue_xmit->__dev_xmit_skb->qdisc_run->__qdisc_run->qdisc_restart->dequeue_skb:
	if ((q->flags & TCQ_F_ONETXQUEUE) &&
		netif_xmit_frozen_or_stopped(txq)) // __QUEUE_STATE_STACK_XOFF is set

Net core will stop transmitting any more. Finillay, net watchdong would timeout.
To fix this issue, we should call netdev_tx_reset_queue() in stmmac_resume().

Fixes: 54139cf3bb33 ("net: stmmac: adding multiple buffers for rx")
Signed-off-by: Joakim Zhang <qiangqing.zhang@....com>
Signed-off-by: Jakub Kicinski <kuba@...nel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
 drivers/net/ethernet/stmicro/stmmac/stmmac_main.c |    2 ++
 1 file changed, 2 insertions(+)

--- a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
+++ b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
@@ -4566,6 +4566,8 @@ static void stmmac_reset_queues_param(st
 		tx_q->cur_tx = 0;
 		tx_q->dirty_tx = 0;
 		tx_q->mss = 0;
+
+		netdev_tx_reset_queue(netdev_get_tx_queue(priv->dev, queue));
 	}
 }