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From: Yunsheng Lin <linyunsheng@huawei.com>
To: Eric Dumazet <eric.dumazet@gmail.com>,
	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>
Subject: Re: [PATCH net-next] net: sch_generic: aviod concurrent reset and enqueue op for lockless qdisc
Date: Wed, 2 Sep 2020 16:14:48 +0800	[thread overview]
Message-ID: <6984825d-1ef7-bf58-75fe-cee1bafe3c1a@huawei.com> (raw)
In-Reply-To: <1f7208e6-8667-e542-88dd-bd80a6c59fd2@gmail.com>

On 2020/9/2 15:32, Eric Dumazet wrote:
> 
> 
> On 9/1/20 11:34 PM, Yunsheng Lin wrote:
> 
>>
>> I am not familiar with TCQ_F_CAN_BYPASS.
>> From my understanding, the problem is that there is no order between
>> qdisc enqueuing and qdisc reset.
> 
> Thw qdisc_reset() should be done after rcu grace period, when there is guarantee no enqueue is in progress.
> 
> qdisc_destroy() already has a qdisc_reset() call, I am not sure why qdisc_deactivate() is also calling qdisc_reset()

That is a good point.
Do we allow skb left in qdisc when the qdisc is deactivated state?
And qdisc_destroy() is not always called after qdisc_deactivate() is called.
If we allow skb left in qdisc when the qdisc is deactivated state, then it is
huge change of semantics for qdisc_deactivate(), and I am not sure how many
cases will affected by this change.


> 
> 
> 

  reply	other threads:[~2020-09-02  8:15 UTC|newest]

Thread overview: 23+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-09-01  0:55 Yunsheng Lin
2020-09-01  6:48 ` Eric Dumazet
2020-09-01  7:27   ` Yunsheng Lin
2020-09-01 18:34     ` David Miller
2020-09-02  1:43       ` Yunsheng Lin
2020-09-01 18:24 ` Cong Wang
2020-09-02  1:42   ` Yunsheng Lin
2020-09-02  4:41     ` Cong Wang
2020-09-02  6:34       ` Yunsheng Lin
2020-09-02  7:32         ` Eric Dumazet
2020-09-02  8:14           ` Yunsheng Lin [this message]
2020-09-02  9:20             ` Eric Dumazet
2020-09-03  1:14               ` Yunsheng Lin
2020-09-03  7:24                 ` Eric Dumazet
2020-09-04  8:10                   ` Yunsheng Lin
2020-09-03  0:35         ` Cong Wang
2020-09-03  1:21           ` Yunsheng Lin
2020-09-03  1:48             ` Cong Wang
2020-09-03  2:22               ` Yunsheng Lin
2020-09-03  2:53                 ` Cong Wang
2020-09-04  1:30                   ` John Fastabend
2020-09-04  8:08                     ` Yunsheng Lin
2020-09-06  8:52 ` [net] 6fd0d0dede: hwsim.ap_ht40_5ghz_switch.fail kernel test robot

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