linux-kernel - Re: [GIT] Networking

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Message-ID: <1281955361.2524.35.camel@edumazet-laptop>
Date:	Mon, 16 Aug 2010 12:42:41 +0200
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	Jarek Poplawski <jarkao2@...il.com>
Cc:	David Miller <davem@...emloft.net>, torvalds@...ux-foundation.org,
	akpm@...ux-foundation.org, netdev@...r.kernel.org,
	linux-kernel@...r.kernel.org, Patrick McHardy <kaber@...sh.net>
Subject: Re: [GIT] Networking

Le lundi 16 août 2010 à 09:53 +0000, Jarek Poplawski a écrit :
> Eric Dumazet wrote:
> > Le dimanche 15 aou^t 2010 a` 12:55 +0200, Eric Dumazet a écrit :
> ...
> > [PATCH] netfilter: {ip,ip6,arp}_tables: avoid lockdep false positive
> > 
> > After commit 24b36f019 (netfilter: {ip,ip6,arp}_tables: dont block
> > bottom half more than necessary), lockdep can raise a warning
> > because we attempt to lock a spinlock with BH enabled, while
> > the same lock is usually locked by another cpu in a softirq context.
> 
> Btw, could you remind us how get_counters() are serialized (I guess
> you can't have them on 2 cpus at the same time)?
> 

get_counters() is serialized by the xt_find_table_lock() done from
get_entries(). This use a mutex to guard against changes.

You are right that if we ever allow two concurrent "iptables -nvL"
operations in the future (using a read lock on a rwlock instead of a
mutex), then we must disable BH even for summing data from the other
cpus.

Thanks


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