From: Vlad Buslov <vladbu@mellanox.com>
To: Cong Wang <xiyou.wangcong@gmail.com>
Cc: Vlad Buslov <vladbu@mellanox.com>,
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 2/3] net: sched: multiq: don't call qdisc_put() while holding tree lock
Date: Thu, 19 Sep 2019 08:56:42 +0000 [thread overview]
Message-ID: <vbfwoe4k6k7.fsf@mellanox.com> (raw)
In-Reply-To: <CAM_iQpV75h9npv2TbBMoRAMf+riPqJhAY2LaiVX-mrVGaUN-Kw@mail.gmail.com>
On Thu 19 Sep 2019 at 01:56, Cong Wang <xiyou.wangcong@gmail.com> wrote:
> On Wed, Sep 18, 2019 at 12:32 AM Vlad Buslov <vladbu@mellanox.com> wrote:
>> diff --git a/net/sched/sch_multiq.c b/net/sched/sch_multiq.c
>> index e1087746f6a2..4cfa9a7bd29e 100644
>> --- a/net/sched/sch_multiq.c
>> +++ b/net/sched/sch_multiq.c
>> @@ -187,18 +187,21 @@ static int multiq_tune(struct Qdisc *sch, struct nlattr *opt,
>>
>> sch_tree_lock(sch);
>> q->bands = qopt->bands;
>> + sch_tree_unlock(sch);
>> +
>> for (i = q->bands; i < q->max_bands; i++) {
>> if (q->queues[i] != &noop_qdisc) {
>> struct Qdisc *child = q->queues[i];
>>
>> + sch_tree_lock(sch);
>> q->queues[i] = &noop_qdisc;
>> qdisc_tree_flush_backlog(child);
>> + sch_tree_unlock(sch);
>> +
>> qdisc_put(child);
>> }
>> }
>
> Repeatedly acquiring and releasing a spinlock in a loop
> does not seem to be a good idea. Is it possible to save
> those qdisc pointers to an array or something similar?
>
> Thanks.
Sure. I implemented it the way I did because following loop in
multiq_tune() is implemented in exactly the same way: it repeatedly
acquires and releases sch tree lock for each new default Qdisc that it
creates.
next prev parent reply other threads:[~2019-09-19 8:56 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-09-18 7:31 [PATCH net 0/3] Fix Qdisc destroy issues caused by adding fine-grained locking to filter API Vlad Buslov
2019-09-18 7:31 ` [PATCH net 1/3] net: sched: sch_htb: don't call qdisc_put() while holding tree lock Vlad Buslov
2019-09-18 7:32 ` [PATCH net 2/3] net: sched: multiq: " Vlad Buslov
2019-09-18 22:56 ` Cong Wang
2019-09-19 8:56 ` Vlad Buslov [this message]
2019-09-18 7:32 ` [PATCH net 3/3] net: sched: sch_sfb: " Vlad Buslov
2019-09-18 22:50 ` [PATCH net 0/3] Fix Qdisc destroy issues caused by adding fine-grained locking to filter API Cong Wang
2019-09-19 8:53 ` Vlad Buslov
2019-09-19 19:13 ` Cong Wang
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