linux-kernel - [PATCH 5.4 254/355] ibmvnic: dont stop queue in xmit

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Message-Id: <20211115165321.960800692@linuxfoundation.org>
Date:   Mon, 15 Nov 2021 18:02:58 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Abdul Haleem <abdhalee@...ibm.com>,
        Vaishnavi Bhat <vaish123@...ibm.com>,
        Sukadev Bhattiprolu <sukadev@...ux.ibm.com>,
        Dany Madden <drt@...ux.ibm.com>,
        "David S. Miller" <davem@...emloft.net>,
        Sasha Levin <sashal@...nel.org>
Subject: [PATCH 5.4 254/355] ibmvnic: dont stop queue in xmit

From: Sukadev Bhattiprolu <sukadev@...ux.ibm.com>

[ Upstream commit 8878e46fcfd46b19964bd90e13b25dd94cbfc9be ]

If adapter's resetting bit is on, discard the packet but don't stop the
transmit queue - instead leave that to the reset code. With this change,
it is possible that we may get several calls to ibmvnic_xmit() that simply
discard packets and return.

But if we stop the queue here, we might end up doing so just after
__ibmvnic_open() started the queues (during a hard/soft reset) and before
the ->resetting bit was cleared. If that happens, there will be no one to
restart queue and transmissions will be blocked indefinitely.

This can cause a TIMEOUT reset and with auto priority failover enabled,
an unnecessary FAILOVER reset to less favored backing device and then a
FAILOVER back to the most favored backing device. If we hit the window
repeatedly, we can get stuck in a loop of TIMEOUT, FAILOVER, FAILOVER
resets leaving the adapter unusable for extended periods of time.

Fixes: 7f5b030830fe ("ibmvnic: Free skb's in cases of failure in transmit")
Reported-by: Abdul Haleem <abdhalee@...ibm.com>
Reported-by: Vaishnavi Bhat <vaish123@...ibm.com>
Signed-off-by: Sukadev Bhattiprolu <sukadev@...ux.ibm.com>
Reviewed-by: Dany Madden <drt@...ux.ibm.com>
Signed-off-by: David S. Miller <davem@...emloft.net>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 drivers/net/ethernet/ibm/ibmvnic.c | 2 --
 1 file changed, 2 deletions(-)

diff --git a/drivers/net/ethernet/ibm/ibmvnic.c b/drivers/net/ethernet/ibm/ibmvnic.c
index cfe7229593ead..059eaa13e2c6d 100644
--- a/drivers/net/ethernet/ibm/ibmvnic.c
+++ b/drivers/net/ethernet/ibm/ibmvnic.c
@@ -1462,8 +1462,6 @@ static netdev_tx_t ibmvnic_xmit(struct sk_buff *skb, struct net_device *netdev)
 	netdev_tx_t ret = NETDEV_TX_OK;

 	if (test_bit(0, &adapter->resetting)) {
-		if (!netif_subqueue_stopped(netdev, skb))
-			netif_stop_subqueue(netdev, queue_num);
 		dev_kfree_skb_any(skb);

 		tx_send_failed++;
-- 
2.33.0