netdev - Re: [RFC] Applicability of using 'txq_trans

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Message-ID: <20220412103724.54924945@kernel.org>
Date:   Tue, 12 Apr 2022 10:37:24 -0700
From:   Jakub Kicinski <kuba@...nel.org>
To:     Ray Jui <ray.jui@...adcom.com>
Cc:     "David S. Miller" <davem@...emloft.net>, netdev@...r.kernel.org
Subject: Re: [RFC] Applicability of using 'txq_trans_update' during ring
 recovery

On Tue, 12 Apr 2022 10:01:02 -0700 Ray Jui wrote:
> Hi David/Jakub,
> 
> I'd like to run through you on the idea of invoking 'txq_trans_update'
> to update the last TX timestamp in the scenario where we temporarily
> stop the TX queue to do some recovery work. Is it considered an
> acceptable approach to prevent false positive triggering of TX timeout
> during the recovery process?
> 
> I know in general people use 'netif_carrier_off' during the process when
> they reset/change the entire TX/RX ring set and/or other resources on
> the Ethernet card. But in our particular case, we have another driver
> running (i.e., RoCE) on top and setting 'netif_carrier_off' will cause a
> significant side effect on the other driver (e.g., all RoCE QPs will be
> terminated). In addition, for this special recovery work on our driver,
> we are doing it on a per NAPI ring set basis while keeping the traffic
> on other queues running. Using 'netif_carrier_off' will prevent traffic
> running from all other queues that are not going through recovery.

Can you use netif_device_detach() to mark the device as not present?