netdev - Re: [PATCH net] be2net: Signal that the device cannot transmit during reconfiguration

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Date:   Wed, 17 Jul 2019 04:23:28 +0000
From:   Firo Yang <firo.yang@...e.com>
To:     Benjamin Poirier <BPoirier@...e.com>,
        David Miller <davem@...emloft.net>
CC:     Ajit Khaparde <ajit.khaparde@...adcom.com>,
        Sathya Perla <sathya.perla@...adcom.com>,
        Somnath Kotur <somnath.kotur@...adcom.com>,
        Sriharsha Basavapatna <sriharsha.basavapatna@...adcom.com>,
        Saeed Mahameed <saeedm@...lanox.com>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>
Subject: Re: [PATCH net] be2net: Signal that the device cannot transmit during
 reconfiguration

I think there is a problem if dev_watchdog() is triggered before netif_carrier_off(). dev_watchdog() might call ->ndo_tx_timeout(), i.e. be_tx_timeout(), if txq timeout  happens. Thus be_tx_timeout() could still be able to access the memory which is being freed by be_update_queues().

Thanks,
Firo

________________________________________
From: Benjamin Poirier
Sent: Tuesday, July 16, 2019 4:16 PM
To: David Miller
Cc: Ajit Khaparde; Sathya Perla; Somnath Kotur; Sriharsha Basavapatna; Saeed Mahameed; Firo Yang; netdev@...r.kernel.org
Subject: [PATCH net] be2net: Signal that the device cannot transmit during reconfiguration

While changing the number of interrupt channels, be2net stops adapter
operation (including netif_tx_disable()) but it doesn't signal that it
cannot transmit. This may lead dev_watchdog() to falsely trigger during
that time.

Add the missing call to netif_carrier_off(), following the pattern used in
many other drivers. netif_carrier_on() is already taken care of in
be_open().

Signed-off-by: Benjamin Poirier <bpoirier@...e.com>
---
 drivers/net/ethernet/emulex/benet/be_main.c | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/drivers/net/ethernet/emulex/benet/be_main.c b/drivers/net/ethernet/emulex/benet/be_main.c
index 82015c8a5ed7..b7a246b33599 100644
--- a/drivers/net/ethernet/emulex/benet/be_main.c
+++ b/drivers/net/ethernet/emulex/benet/be_main.c
@@ -4697,8 +4697,12 @@ int be_update_queues(struct be_adapter *adapter)
        struct net_device *netdev = adapter->netdev;
        int status;

-       if (netif_running(netdev))
+       if (netif_running(netdev)) {
+               /* device cannot transmit now, avoid dev_watchdog timeouts */
+               netif_carrier_off(netdev);
+
                be_close(netdev);
+       }

        be_cancel_worker(adapter);

--
2.22.0