From: Yunsheng Lin <linyunsheng@huawei.com>
To: Cong Wang <xiyou.wangcong@gmail.com>
Cc: Jamal Hadi Salim <jhs@mojatatu.com>,
Jiri Pirko <jiri@resnulli.us>,
"David Miller" <davem@davemloft.net>,
Jakub Kicinski <kuba@kernel.org>,
"Linux Kernel Network Developers" <netdev@vger.kernel.org>,
LKML <linux-kernel@vger.kernel.org>, <linuxarm@huawei.com>,
John Fastabend <john.fastabend@gmail.com>,
Eric Dumazet <eric.dumazet@gmail.com>
Subject: Re: [PATCH v2 net] net: sch_generic: aviod concurrent reset and enqueue op for lockless qdisc
Date: Thu, 5 Nov 2020 14:32:52 +0800 [thread overview]
Message-ID: <feea91bc-c189-f28b-ca5d-d0bc6c031c3f@huawei.com> (raw)
In-Reply-To: <CAM_iQpXZHPSW9j+DaUDZdqm+wGrmy4nLL8gPEm7g3XndPn90+Q@mail.gmail.com>
On 2020/11/5 14:16, Cong Wang wrote:
> On Wed, Nov 4, 2020 at 10:04 PM Cong Wang <xiyou.wangcong@gmail.com> wrote:
>>
>> On Mon, Nov 2, 2020 at 11:24 PM Yunsheng Lin <linyunsheng@huawei.com> wrote:
>>>>> From my understanding, we can do anything about the old qdisc (including
>>>>> destorying the old qdisc) after some_qdisc_is_busy() return false.
>>>>
>>>> But the current code does the reset _before_ some_qdisc_is_busy(). ;)
>>>
>>> If lock is taken when doing reset, it does not matter if the reset is
>>> before some_qdisc_is_busy(), right?
>>
>> Why not? How about the following scenario?
>>
>> CPU0: CPU1:
>> dev_reset_queue()
>> net_tx_action()
>> -> sch_direct_xmit()
>> -> dev_requeue_skb()
>> some_qdisc_is_busy()
>> // waiting for TX action on CPU1
>> // now some packets are requeued
>
> Never mind, the skb_bad_txq is also cleared by dev_reset_queue().
> TX action after resetting should get NULL.
Yes, maybe it is safe to remove qdisc_reset() now? or issue a warning
if there are still skb in the qdisc.
>
> Thanks.
> .
>
next prev parent reply other threads:[~2020-11-05 6:33 UTC|newest]
Thread overview: 25+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-09-08 11:02 Yunsheng Lin
2020-09-10 19:39 ` David Miller
2020-09-10 20:07 ` Cong Wang
2020-09-11 8:13 ` Yunsheng Lin
2020-09-11 8:25 ` Yunsheng Lin
2020-09-17 19:26 ` Cong Wang
[not found] ` <CAP12E-+3DY-dgzVercKc-NYGPExWO1NjTOr1Gf3tPLKvp6O6+g@mail.gmail.com>
2020-10-28 15:37 ` Pai, Vishwanath
2020-10-28 17:47 ` Cong Wang
2020-10-28 20:04 ` Vishwanath Pai
2020-10-29 2:37 ` Yunsheng Lin
2020-10-29 4:50 ` Vishwanath Pai
2020-10-29 10:24 ` Yunsheng Lin
2020-10-29 17:20 ` Vishwanath Pai
2020-11-02 9:08 ` Yunsheng Lin
2020-11-02 18:23 ` Vishwanath Pai
2020-10-28 17:46 ` Vishwanath Pai
2020-10-29 2:52 ` Yunsheng Lin
2020-10-29 19:05 ` Cong Wang
2020-10-30 7:37 ` Yunsheng Lin
2020-11-02 16:55 ` Cong Wang
2020-11-03 7:24 ` Yunsheng Lin
2020-11-05 6:04 ` Cong Wang
2020-11-05 6:16 ` Cong Wang
2020-11-05 6:32 ` Yunsheng Lin [this message]
2020-11-05 6:22 ` Yunsheng Lin
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