From mboxrd@z Thu Jan  1 00:00:00 1970
From: Eric Dumazet <eric.dumazet@gmail.com>
Subject: Re: [PATCH 1/2] ipv6: do not hold route table lock when send ndisc
 probe
Date: Thu, 23 Aug 2012 18:10:32 +0200
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Cc: Debabrata Banerjee <dbavatar@gmail.com>, netdev@vger.kernel.org,
	"Banerjee, Debabrata" <dbanerje@akamai.com>,
	"David S. Miller" <davem@davemloft.net>,
	Hideaki YOSHIFUJI <yoshfuji@linux-ipv6.org>,
	Patrick McHardy <kaber@trash.net>
To: Cong Wang <amwang@redhat.com>
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On Tue, 2012-08-21 at 11:44 +0800, Cong Wang wrote:
> Hi, Debabrata,
> 
> Could you help to test the attached patch below?
> 
> Thanks!
> 

Hard to comment on your patch since its not inlined.

+               nw = kmalloc(sizeof(*nw), GFP_ATOMIC);
+               if (nw) {
+                       memcpy(&nw->target, &neigh->primary_key, sizeof(struct in6_addr));
+                       addrconf_addr_solict_mult(&nw->target, &nw->mcaddr);
+                       nw->dev = rt->dst.dev;
+                       INIT_WORK(&nw->work, queue_ndisc);
+                       schedule_work(&nw->work);
+               }

You cant do that without taking extra reference on dev,
and release it in queue_ndisc()

This also will add interesting side effects at device dismantle.