----- On Feb 17, 2016, at 7:47 AM, Phil Sutter phil@xxxxxx wrote:
> Hi,
>
> On Tue, Feb 16, 2016 at 07:56:23PM -0500, Mathieu Desnoyers wrote:
>> This reverts commit 348e3435cbefa815bd56a5205c1412b5afe7b92e.
>> It breaks HTB classful qdiscs on the loopback interface.
>>
>> It has been broken since kernel v4.2. The offending commit has
>> been identified by bissection of the issue with the following
>> test-case. It appears that the loopback interface does indeed
>> still have tx_queue_len == 0.
>>
>> Reverting the commit on a v4.4.1 kernel fixes the issue.
>
> Indeed, this is ugly. Affected are all drivers not calling ether_setup()
> in their setup callback, and therefore not initializing tx_queue_len.
>
> As the commit to be reverted shows, there is no common fallback value
> for tx_queue_len - most qdisc implementations used 1, but HTB fell back
> to 2 and PLUG to 100. But as the removed comment in sch_plug.c stated:
>
>| /* We will set a default limit of 100 pkts (~150kB)
>| * in case tx_queue_len is not available. The
>| * default value is completely arbitrary.
>| */
>
> It seems not to be overly important to fallback to the exact value each
> qdisc had before. Therefore I guess the following change should
> appropriately fix the issue at hand:
>
> --- a/net/core/dev.c
> +++ b/net/core/dev.c
> @@ -7440,8 +7440,10 @@ struct net_device *alloc_netdev_mqs(int sizeof_priv,
> const char *name,
> dev->priv_flags = IFF_XMIT_DST_RELEASE | IFF_XMIT_DST_RELEASE_PERM;
> setup(dev);
>
> - if (!dev->tx_queue_len)
> + if (!dev->tx_queue_len) {
> dev->priv_flags |= IFF_NO_QUEUE;
> + dev->tx_queue_len = 1;
> + }
>
> dev->num_tx_queues = txqs;
> dev->real_num_tx_queues = txqs;
>
> Unless there is concern, I will formally submit this later.
Works for me!
Tested-by: Mathieu Desnoyers <mathieu.desnoyers@xxxxxxxxxxxx>
Thanks,
Mathieu
>
> Thanks, Phil
--
Mathieu Desnoyers
EfficiOS Inc.
http://www.efficios.com
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