netdev - Re: [PATCH] netpoll: Check for skb->queue

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Message-ID: <1491506056.10124.81.camel@edumazet-glaptop3.roam.corp.google.com>
Date:   Thu, 06 Apr 2017 12:14:16 -0700
From:   Eric Dumazet <eric.dumazet@...il.com>
To:     tndave <tushar.n.dave@...cle.com>
Cc:     davem@...emloft.net, edumazet@...gle.com, brouer@...hat.com,
        netdev@...r.kernel.org, sowmini.varadhan@...cle.com
Subject: Re: [PATCH] netpoll: Check for skb->queue_mapping

On Thu, 2017-04-06 at 12:07 -0700, tndave wrote:

> > +			q_index = q_index % dev->real_num_tx_queues;
> cpu interrupted here and dev->real_num_tx_queues has reduced!
> > +			skb_set_queue_mapping(skb, q_index);
> > +		}
> > +		txq = netdev_get_tx_queue(dev, q_index);
> or cpu interrupted here and dev->real_num_tx_queues has reduced!

If dev->real_num_tx_queues can be changed while this code is running we
are in deep deep trouble.

Better make sure that when control path does this change, device (and/pr
netpoll) is frozen and no packet can be sent.