netdev - Re: [PATCH linux] net: fix deadlock while clearing neighbor proxy table

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Message-Id: <20180410.110229.1597289057689247263.davem@davemloft.net>
Date:   Tue, 10 Apr 2018 11:02:29 -0400 (EDT)
From:   David Miller <davem@...emloft.net>
To:     w.bumiller@...xmox.com
Cc:     netdev@...r.kernel.org, yoshfuji@...ux-ipv6.org
Subject: Re: [PATCH linux] net: fix deadlock while clearing neighbor proxy
 table

From: Wolfgang Bumiller <w.bumiller@...xmox.com>
Date: Tue, 10 Apr 2018 11:15:14 +0200

> diff --git a/net/core/neighbour.c b/net/core/neighbour.c
> index 7b7a14abba28..601df647588c 100644
> --- a/net/core/neighbour.c
> +++ b/net/core/neighbour.c
> @@ -292,7 +292,6 @@ int neigh_ifdown(struct neigh_table *tbl, struct net_device *dev)
>  	write_lock_bh(&tbl->lock);
>  	neigh_flush_dev(tbl, dev);
>  	pneigh_ifdown(tbl, dev);
> -	write_unlock_bh(&tbl->lock);

If we are going to fix it this way, we need to annotate the code here in some
way so that future readers understand why the tbl->lock is not being released
here.

One way is to add a comment.

Another way is to rename pneigh_ifdown() to "pneigh_ifdown_and_unlock()".