netdev - Re: [PATCH] netfilter: use per-cpu recursive spinlock (v6)

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Date:	Thu, 16 Apr 2009 18:20:04 +0200
From:	Eric Dumazet <dada1@...mosbay.com>
To:	paulmck@...ux.vnet.ibm.com
CC:	Patrick McHardy <kaber@...sh.net>,
	Stephen Hemminger <shemminger@...tta.com>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	David Miller <davem@...emloft.net>, 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: use per-cpu recursive spinlock  (v6)

Eric Dumazet a écrit :

> I also considered using regular spinlocks and spin_trylock() to "detect"
> the recurse case without a global counter.
> 
> lock :
> local_bh_disable();
> int locked = spin_trylock(&__get_cpu_var(arp_tables_lock);
> 
> unlock:
> 
> if (likely(locked))
> 	spin_unlock(&__get_cpu_var(arp_tables_lock));
> local_bh_enable();
> 
> But we would lose some runtime features, I dont feel comfortable about
> this trylock version. What others people think ?
> 

Oh well, this wont work of course, forget about this trylock thing :)

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