From: Vlad Buslov <vladbu@mellanox.com>
To: Cong Wang <xiyou.wangcong@gmail.com>
Cc: Linux Kernel Network Developers <netdev@vger.kernel.org>,
Jamal Hadi Salim <jhs@mojatatu.com>,
Jiri Pirko <jiri@resnulli.us>, David Miller <davem@davemloft.net>
Subject: Re: [PATCH net-next 09/12] net: sched: flower: handle concurrent tcf proto deletion
Date: Tue, 19 Feb 2019 14:08:46 +0000 [thread overview]
Message-ID: <vbf1s43rhud.fsf@mellanox.com> (raw)
In-Reply-To: <CAM_iQpWdKR1JJsqarzLSuzaUDfPeTzPZMjCUb-ENj8aG62v_nA@mail.gmail.com>
On Mon 18 Feb 2019 at 20:47, Cong Wang <xiyou.wangcong@gmail.com> wrote:
> On Wed, Feb 13, 2019 at 11:47 PM Vlad Buslov <vladbu@mellanox.com> wrote:
>>
>> Without rtnl lock protection tcf proto can be deleted concurrently. Check
>> tcf proto 'deleting' flag after taking tcf spinlock to verify that no
>> concurrent deletion is in progress. Return EAGAIN error if concurrent
>> deletion detected, which will cause caller to retry and possibly create new
>> instance of tcf proto.
>>
>
> Please state the reason why you prefer retry over locking the whole
> tp without retrying, that is why and how it is better?
>
> Personally I always prefer non-retry logic, because it is very easy
> to understand and justify its correctness.
>
> As you prefer otherwise, please share your reasoning in changelog.
>
> Thanks!
At the moment filter removal code is implemented by cls API in following
fashion:
1) tc_del_tfilter() obtains opaque void pointer to filter by calling
tp->ops->get()
2) Pass filter pointer to tfilter_del_notify() which prepares skb with
all necessary info about filter that is being removed and...
3) ... calls tp->ops->delete() to actually delete filter.
Between 1) and 3) filter can be removed concurrently and there is
nothing we can do about it in flower, besides account for that with some
kind of retry logic. I will explain why I prefer cls API to not just
lock whole classifier instance when modifying it in any way in reply to
cls API patch "net: sched: protect filter_chain list with
filter_chain_lock mutex" discussion.
next prev parent reply other threads:[~2019-02-19 14:08 UTC|newest]
Thread overview: 44+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-02-14 7:47 [PATCH net-next 00/12] Refactor flower classifier to remove dependency on rtnl lock Vlad Buslov
2019-02-14 7:47 ` [PATCH net-next 01/12] net: sched: flower: don't check for rtnl on head dereference Vlad Buslov
2019-02-18 19:08 ` Cong Wang
2019-02-19 9:45 ` Vlad Buslov
2019-02-20 22:33 ` Cong Wang
2019-02-21 17:45 ` Vlad Buslov
2019-02-22 19:32 ` Cong Wang
2019-02-25 16:11 ` Vlad Buslov
2019-02-25 22:39 ` Cong Wang
2019-02-26 14:57 ` Vlad Buslov
2019-02-28 0:49 ` Cong Wang
2019-02-28 18:35 ` Vlad Buslov
2019-03-02 0:51 ` Cong Wang
2019-02-14 7:47 ` [PATCH net-next 02/12] net: sched: flower: refactor fl_change Vlad Buslov
2019-02-14 20:34 ` Stefano Brivio
2019-02-15 10:38 ` Vlad Buslov
2019-02-15 10:47 ` Stefano Brivio
2019-02-15 16:25 ` Vlad Buslov
2019-02-18 18:20 ` Stefano Brivio
2019-02-14 7:47 ` [PATCH net-next 03/12] net: sched: flower: introduce reference counting for filters Vlad Buslov
2019-02-14 20:34 ` Stefano Brivio
2019-02-15 11:22 ` Vlad Buslov
2019-02-15 12:32 ` Stefano Brivio
2019-02-14 7:47 ` [PATCH net-next 04/12] net: sched: flower: track filter deletion with flag Vlad Buslov
2019-02-14 20:49 ` Stefano Brivio
2019-02-15 15:54 ` Vlad Buslov
2019-02-14 7:47 ` [PATCH net-next 05/12] net: sched: flower: add reference counter to flower mask Vlad Buslov
2019-02-14 7:47 ` [PATCH net-next 06/12] net: sched: flower: handle concurrent mask insertion Vlad Buslov
2019-02-15 22:46 ` Stefano Brivio
2019-02-14 7:47 ` [PATCH net-next 07/12] net: sched: flower: protect masks list with spinlock Vlad Buslov
2019-02-14 7:47 ` [PATCH net-next 08/12] net: sched: flower: handle concurrent filter insertion in fl_change Vlad Buslov
2019-02-14 7:47 ` [PATCH net-next 09/12] net: sched: flower: handle concurrent tcf proto deletion Vlad Buslov
2019-02-18 20:47 ` Cong Wang
2019-02-19 14:08 ` Vlad Buslov [this message]
2019-02-14 7:47 ` [PATCH net-next 10/12] net: sched: flower: protect flower classifier state with spinlock Vlad Buslov
2019-02-14 7:47 ` [PATCH net-next 11/12] net: sched: flower: track rtnl lock state Vlad Buslov
2019-02-15 22:46 ` Stefano Brivio
2019-02-18 9:35 ` Vlad Buslov
2019-02-14 7:47 ` [PATCH net-next 12/12] net: sched: flower: set unlocked flag for flower proto ops Vlad Buslov
2019-02-18 19:27 ` Cong Wang
2019-02-19 10:15 ` Vlad Buslov
2019-02-20 22:36 ` Cong Wang
2019-02-18 19:15 ` [PATCH net-next 00/12] Refactor flower classifier to remove dependency on rtnl lock Cong Wang
2019-02-19 10:00 ` Vlad Buslov
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