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

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Date:	Fri, 18 Jul 2014 07:37:03 +0200
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	Cong Wang <xiyou.wangcong@...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, 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.

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



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