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

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Date:	Fri, 01 Jul 2016 07:18:10 +0200
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	Yuval Mintz <Yuval.Mintz@...gic.com>
Cc:	Saeed Mahameed <saeedm@....mellanox.co.il>,
	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, 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.