netdev - Re: [Patch net-next] net_sched: hold tcf

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Message-ID: <CAM_iQpWO-SS0rEVp+Nmxd9N8O0UvtpufVj8ozc3csStuVtKshA@mail.gmail.com>
Date:	Thu, 17 Jul 2014 22:51:53 -0700
From:	Cong Wang <xiyou.wangcong@...il.com>
To:	Eric Dumazet <eric.dumazet@...il.com>
Cc:	Jamal Hadi Salim <jhs@...atatu.com>,
	Linux Kernel Network Developers <netdev@...r.kernel.org>,
	"David S. Miller" <davem@...emloft.net>,
	Cong Wang <cwang@...pensource.com>
Subject: Re: [Patch net-next] net_sched: hold tcf_lock in netdevice notifier

On Thu, Jul 17, 2014 at 10:37 PM, Eric Dumazet <eric.dumazet@...il.com> wrote:
> On Thu, 2014-07-17 at 14:25 -0700, Cong Wang wrote:
>> On Thu, Jul 17, 2014 at 11:17 AM, Eric Dumazet <eric.dumazet@...il.com> wrote:
>> >
>> > Anyway, tcfm_dev should probably be RCU protected.
>> >
>>
>> Not sure how much we gain from making it RCU. We anyway
>> need to hold that spinlock on fast path since we need to
>> update its time stamp and stats.
>>
>> I would just leave it as is.
>
>
> I think you really should look at John Fastabend work, and many other
> existing paths in the stack.
>

I reviewed the last two verions of his patchset...


> All this can be done lockless in fast path, using RCU and percpu
> counters.
>

I don't think he ever removes this m->tcf_lock.
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