netdev - Re: [PATCH] netfilter: per-cpu spin-lock with recursion (v0.8)

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Date:	Fri, 17 Apr 2009 19:08:15 +0200
From:	Peter Zijlstra <peterz@...radead.org>
To:	Eric Dumazet <dada1@...mosbay.com>
Cc:	Stephen Hemminger <shemminger@...tta.com>,
	paulmck@...ux.vnet.ibm.com, David Miller <davem@...emloft.net>,
	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
Subject: Re: [PATCH] netfilter: per-cpu spin-lock with recursion (v0.8)

On Fri, 2009-04-17 at 08:14 +0200, Eric Dumazet wrote:
> > Also, please dont call this a 'recursive lock', since it is not a general
> > recursive lock, as pointed by Linus and Paul.
> > 
> > Second question is about MAX_LOCK_DEPTH
> 
> I meant here the ~256 limit we have on preempt_count, not related to LOCKDEP

Very good point, so 256 nested spin_lock() instances will make the
kernel unhappy -- since we now (almost?) support up to 4096 cpus, this
seems like a no-no.

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