From: Vlad Buslov <vladbu@mellanox.com>
To: Stefano Brivio <sbrivio@redhat.com>
Cc: "netdev@vger.kernel.org" <netdev@vger.kernel.org>,
"jhs@mojatatu.com" <jhs@mojatatu.com>,
"xiyou.wangcong@gmail.com" <xiyou.wangcong@gmail.com>,
"jiri@resnulli.us" <jiri@resnulli.us>,
"davem@davemloft.net" <davem@davemloft.net>
Subject: Re: [PATCH net-next v2 04/12] net: sched: flower: track filter deletion with flag
Date: Mon, 4 Mar 2019 14:24:05 +0000 [thread overview]
Message-ID: <vbfpnr6ogzi.fsf@mellanox.com> (raw)
In-Reply-To: <20190302005129.4d4508c9@redhat.com>
On Fri 01 Mar 2019 at 23:51, Stefano Brivio <sbrivio@redhat.com> wrote:
> Hi Vlad,
>
> On Wed, 27 Feb 2019 12:12:18 +0200
> Vlad Buslov <vladbu@mellanox.com> wrote:
>
>> -static bool __fl_delete(struct tcf_proto *tp, struct cls_fl_filter *f,
>> - struct netlink_ext_ack *extack)
>> +static int __fl_delete(struct tcf_proto *tp, struct cls_fl_filter *f,
>> + bool *last, struct netlink_ext_ack *extack)
>> {
>> struct cls_fl_head *head = fl_head_dereference(tp);
>> bool async = tcf_exts_get_net(&f->exts);
>> - bool last;
>>
>> + *last = false;
>> +
>> + if (f->deleted)
>> + return -ENOENT;
>> +
>> + f->deleted = true;
>
> Now that I can read this more easily :) I have a doubt: you say this
> flag "prevent[s] double deletion of filter by concurrent tasks".
>
> However, if this has no further protections (which I can't readily
> see), I think this is racy:
>
> task 1 task 2
> if (f->deleted) [false]
> if (f->deleted) [false]
> f->deleted = true; f->deleted = true;
>
> what am I missing here?
Of course! Lock is added in "[PATCH net-next v2 10/12] net: sched:
flower: protect flower classifier state with spinlock". This is safe to
do because everything is still protected by rtnl mutex until last patch
in this series sets the TCF_PROTO_OPS_DOIT_UNLOCKED flag for flower.
next prev parent reply other threads:[~2019-03-04 14:24 UTC|newest]
Thread overview: 19+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-02-27 10:12 [PATCH net-next v2 00/12] Refactor flower classifier to remove dependency on rtnl lock Vlad Buslov
2019-02-27 10:12 ` [PATCH net-next v2 01/12] net: sched: flower: don't check for rtnl on head dereference Vlad Buslov
2019-02-27 10:12 ` [PATCH net-next v2 02/12] net: sched: flower: refactor fl_change Vlad Buslov
2019-02-27 10:12 ` [PATCH net-next v2 03/12] net: sched: flower: introduce reference counting for filters Vlad Buslov
2019-02-27 10:12 ` [PATCH net-next v2 04/12] net: sched: flower: track filter deletion with flag Vlad Buslov
2019-03-01 23:51 ` Stefano Brivio
2019-03-04 14:24 ` Vlad Buslov [this message]
2019-03-04 23:56 ` Stefano Brivio
2019-02-27 10:12 ` [PATCH net-next v2 05/12] net: sched: flower: add reference counter to flower mask Vlad Buslov
2019-02-27 10:12 ` [PATCH net-next v2 06/12] net: sched: flower: handle concurrent mask insertion Vlad Buslov
2019-02-27 10:12 ` [PATCH net-next v2 07/12] net: sched: flower: protect masks list with spinlock Vlad Buslov
2019-02-27 10:12 ` [PATCH net-next v2 08/12] net: sched: flower: handle concurrent filter insertion in fl_change Vlad Buslov
2019-02-27 10:12 ` [PATCH net-next v2 09/12] net: sched: flower: handle concurrent tcf proto deletion Vlad Buslov
2019-02-27 10:12 ` [PATCH net-next v2 10/12] net: sched: flower: protect flower classifier state with spinlock Vlad Buslov
2019-02-27 10:12 ` [PATCH net-next v2 11/12] net: sched: flower: track rtnl lock state Vlad Buslov
2019-02-27 10:12 ` [PATCH net-next v2 12/12] net: sched: flower: set unlocked flag for flower proto ops Vlad Buslov
2019-03-04 18:28 ` [PATCH net-next v2 00/12] Refactor flower classifier to remove dependency on rtnl lock David Miller
2019-03-04 23:57 ` Stefano Brivio
2019-03-06 11:52 ` Vlad Buslov
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