netdev - Re: [PATCH net] net: poll tx timeout only on active tx queues

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Message-ID: <CALzJLG9tiqPUe=h+OhTSqaS1ULkOtG3ycaZQXGrvtbgL3deH6g@mail.gmail.com>
Date:	Fri, 1 Jul 2016 15:03:00 +0300
From:	Saeed Mahameed <saeedm@....mellanox.co.il>
To:	Eric Dumazet <eric.dumazet@...il.com>
Cc:	Yuval Mintz <Yuval.Mintz@...gic.com>,
	Saeed Mahameed <saeedm@...lanox.com>,
	David Miller <davem@...emloft.net>,
	netdev <netdev@...r.kernel.org>,
	Eric Dumazet <edumazet@...gle.com>,
	Tom Herbert <tom@...bertland.com>,
	Mohamad Haj Yahia <mohamad@...lanox.com>
Subject: Re: [PATCH net] net: poll tx timeout only on active tx queues

On Fri, Jul 1, 2016 at 8:18 AM, Eric Dumazet <eric.dumazet@...il.com> wrote:
> On Fri, 2016-07-01 at 04:50 +0000, Yuval Mintz wrote:
>> > currently all the device driver call  netif_tx_start_all_queues(dev)
>> > on open to W/A this issue. which is strange since only
>> > real_num_tx_queues are active.
>>
>> You could also argue that netif_tx_start_all_queues() should
>> only enable the real_num_tx_queues.
>> [Although that would obviously cause all drivers to reach the
>> 'problem' you're currently fixing].
>
> Yep. Basically what I pointed out.
>
> It seems inconsistent to have loops using num_tx_queues, and others
> using real_num_tx_queues.
>
> Instead of 'fixing' one of them, we should take a deeper look, even if
> the change looks fine.
>
> num_tx_queues should be used in code that runs once, like
> netdev_lockdep_set_classes(), but other loops should probably use
> real_num_tx_queues.
>
> Anyway all these changes should definitely target net-next, not net
> tree.
>

Thank you Eric and Yuval,

Although i slightly disagree, this patch is good as is, even with the
inconsistency, which is there due to a bad design.
I don't' see why new drivers need to keep copy from old wrong
implementations and workarounds.

But for the long term, you have a point.
We will consider a deeper fix for net-next as you suggested, and drop
this temporary fix.

Thanks
Saeed.