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Subject: Re: [PATCH] netfilter: xtables: stackptr should be percpu
From: Eric Dumazet <eric.dumazet@gmail.com>
To: Jan Engelhardt <jengelh@medozas.de>
Cc: Xiaotian Feng <dfeng@redhat.com>, netfilter-devel@vger.kernel.org,
       netfilter@vger.kernel.org, coreteam@netfilter.org,
       linux-kernel@vger.kernel.org, netdev@vger.kernel.org,
       Patrick McHardy <kaber@trash.net>,
       "David S. Miller" <davem@davemloft.net>,
       Andrew Morton <akpm@linux-foundation.org>,
       Rusty Russell <rusty@rustcorp.com.au>,
       Alexey Dobriyan <adobriyan@gmail.com>
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Date: Mon, 31 May 2010 15:44:08 +0200
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Le lundi 31 mai 2010 à 15:22 +0200, Jan Engelhardt a écrit :
> On Monday 2010-05-31 15:13, Eric Dumazet wrote:
> >
> >All cpus share a single cache line for their 'stackptr' storage,
> >introduced in commit f3c5c1bfd4
> >
> >This is a stable candidate (2.6.34)
> 
> Stackptr was first introduced for 2.6.35-rcX.
> 

Indeed, I was fooled by 'git describe'

> >+	i->stackptr = alloc_percpu(unsigned int);
> > 	if (i->stackptr == NULL)
> > 		return -ENOMEM;
> >-	memset(i->stackptr, 0, size);
> > 
> > 	size = sizeof(void **) * nr_cpu_ids;
> > 	if (size > PAGE_SIZE)
> 
> Are alloc_percpu areas cleared?
> 

Yes, allocated chunks are cleared.