linux-kernel - Re: [PATCH] netfilter: use per-cpu spinlock rather than RCU (v3)

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Message-Id: <20090417.010710.59150850.davem@davemloft.net>
Date:	Fri, 17 Apr 2009 01:07:10 -0700 (PDT)
From:	David Miller <davem@...emloft.net>
To:	paulmck@...ux.vnet.ibm.com
Cc:	dada1@...mosbay.com, shemminger@...tta.com, kaber@...sh.net,
	torvalds@...ux-foundation.org, jeff.chua.linux@...il.com,
	paulus@...ba.org, mingo@...e.hu, laijs@...fujitsu.com,
	jengelh@...ozas.de, r000n@...0n.net, linux-kernel@...r.kernel.org,
	netfilter-devel@...r.kernel.org, netdev@...r.kernel.org,
	benh@...nel.crashing.org, mathieu.desnoyers@...ymtl.ca
Subject: Re: [PATCH] netfilter: use per-cpu spinlock rather than RCU (v3)

From: "Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
Date: Thu, 16 Apr 2009 22:40:32 -0700

> I completely agree that this RCU is absolutely -not- 2.6.30 material.  ;-)

I don't understand why we're writing such complicated code.

Oh I see why, it's because not every arch uses the generic SMP helpers
yet :-)

Because if they did universally, we could solve this problem so
simply, by merely sending a remote softirq to every online cpu.  Once
those all complete we have enough of a quiesce period, every cpu must
have exited any netfilter packet processing code path they were in.

And we could know they complete using an atomic counter or something.
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