netdev - Re: Sparse Warnings: net/ipv6/route.c:521:17: sparse: context imbalance in 'rt6_probe'

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Message-Id: <20130121.154803.1415897555788515730.davem@davemloft.net>
Date:	Mon, 21 Jan 2013 15:48:03 -0500 (EST)
From:	David Miller <davem@...emloft.net>
To:	PeterHuewe@....de
Cc:	yoshfuji@...ux-ipv6.org, fengguang.wu@...el.com,
	netdev@...r.kernel.org
Subject: Re: Sparse Warnings: net/ipv6/route.c:521:17: sparse: context
 imbalance in 'rt6_probe' - different lock contexts for basic block

From: Peter Hüwe <PeterHuewe@....de>
Date: Mon, 21 Jan 2013 21:03:17 +0100

> Hi YOSHIFUJI,
> 
> FYI, there are new sparse warnings show up in
> 
> tree:   git://git.kernel.org/pub/scm/linux/kernel/git/davem/net-next.git
> branch: master
> head:   887c95cc1da53f66a5890fdeab13414613010097
> commit: 2152caea719657579daa3a1a57a5425a3db6d612 [185/189] ipv6: Do not depend 
> on rt->n in rt6_probe().
> 
>>> net/ipv6/route.c:521:17: sparse: context imbalance in 'rt6_probe' - 
> different lock contexts for basic block
> 
> On latest net-next/master it's
> net/ipv6/route.c:500:17: warning: context imbalance in 'rt6_probe' - different 
> lock contexts for basic block
> 
> 
> Reported-by: Fengguang Wu <fengguang.wu@...el.com>
> Reported-by: Peter Huewe <peterhuewe@....de>

This is fixed by:

commit b820bb6b996966d93a5442b5fbf803ea58e7f487
Author: YOSHIFUJI Hideaki / 吉藤英明 <yoshfuji@...ux-ipv6.org>
Date:   Mon Jan 21 09:58:50 2013 +0000

    ndisc: Do not try to update "updated" time if neighbour has already gone.
    
    Commit 2152caea ("ipv6: Do not depend on rt->n in rt6_probe().")
    introduce a bug to try to update "updated" time in neighbour
    structure.
    Update the "updated" time only if neighbour is available.
    
    Bug was found by Dan Carpenter <dan.carpenter@...cle.com>
    
    Signed-off-by: YOSHIFUJI Hideaki <yoshfuji@...ux-ipv6.org>
    Signed-off-by: David S. Miller <davem@...emloft.net>

diff --git a/net/ipv6/route.c b/net/ipv6/route.c
index 2d94d5a..f3328bc 100644
--- a/net/ipv6/route.c
+++ b/net/ipv6/route.c
@@ -492,10 +492,10 @@ static void rt6_probe(struct rt6_info *rt)
 		struct in6_addr mcaddr;
 		struct in6_addr *target;
 
-		neigh->updated = jiffies;
-
-		if (neigh)
+		if (neigh) {
+			neigh->updated = jiffies;
 			write_unlock(&neigh->lock);
+		}
 
 		target = (struct in6_addr *)&rt->rt6i_gateway;
 		addrconf_addr_solict_mult(target, &mcaddr);