netdev - Re: [PATCH net v2 1/3] net: sched: sch_htb: don't call qdisc

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Message-ID: <vbfv9tnzdnb.fsf@mellanox.com>
Date:   Fri, 20 Sep 2019 06:27:26 +0000
From:   Vlad Buslov <vladbu@...lanox.com>
To:     Cong Wang <xiyou.wangcong@...il.com>
CC:     Vlad Buslov <vladbu@...lanox.com>,
        Linux Kernel Network Developers <netdev@...r.kernel.org>,
        Jamal Hadi Salim <jhs@...atatu.com>,
        Jiri Pirko <jiri@...nulli.us>,
        David Miller <davem@...emloft.net>
Subject: Re: [PATCH net v2 1/3] net: sched: sch_htb: don't call qdisc_put()
 while holding tree lock


On Fri 20 Sep 2019 at 04:05, Cong Wang <xiyou.wangcong@...il.com> wrote:
> On Thu, Sep 19, 2019 at 1:14 PM Vlad Buslov <vladbu@...lanox.com> wrote:
>> Notes:
>>     Changes V1 -> V2:
>>
>>     - Extend sch API with new qdisc_put_empty() function that has same
>>       implementation as regular qdisc_put() but skips parts that reset qdisc
>>       and free all packet buffers from gso_skb and skb_bad_txq queues.
>
> I don't understand why you need a new API here, as long as qdisc_reset()
> gets called before releasing sch tree lock, the ->reset() inside qdisc_put(),
> after releasing sch tree lock, should be a nop, right?

Yes, but I wanted to make it explicit, so anyone else looking at the
code of those Qdiscs would know that manual reset with appropriate
locking is required. And it didn't require much new code because
qdisc_put() and qidsc_put_empty() just reuse same __qdisc_put(). I'll
revert it back, if you suggest that original approach is better.