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

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Message-ID: <53CAEAE5.3090300@mojatatu.com>
Date:	Sat, 19 Jul 2014 18:02:13 -0400
From:	Jamal Hadi Salim <jhs@...atatu.com>
To:	Eric Dumazet <eric.dumazet@...il.com>,
	Cong Wang <xiyou.wangcong@...il.com>
CC:	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 07/18/14 03:08, Eric Dumazet wrote:
> On Thu, 2014-07-17 at 22:51 -0700, Cong Wang wrote:
>
> If this conversion was already done by John, I would have pointed the
> patch to finalize.
>
> There is nothing fundamental that requires this spinlock being held in
> fast path.
>
> It is perfectly possible to remove this, and first step is to use RCU,
> then percpu counters.
>

I think rcufication would help in some the shared action instances.
Note: post John's rcu-fication of classifier path this is not an
issue i.e
the most common use case default behavior (majority) is no sharing of
instances - in such a case there is no lock contention.

cheers,
jamal
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