netdev - Re: [PATCH] neighbour: Convert if statment in the function, neigh_add_timer to a WARN

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Date:	Tue, 02 Jun 2015 11:37:40 +0900
From:	YOSHIFUJI Hideaki/吉藤英明 
	<hideaki.yoshifuji@...aclelinux.com>
To:	Nicholas Krause <xerofoify@...il.com>, davem@...emloft.net
CC:	hideaki.yoshifuji@...aclelinux.com, ebiederm@...ssion.com,
	edumazet@...gle.com, xiyou.wangcong@...il.com,
	yoshfuji@...ux-ipv6.org, johannes.berg@...el.com,
	nicolas.dichtel@...nd.com, netdev@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] neighbour: Convert if statment in the function, neigh_add_timer
 to a WARN_ON

Nicholas Krause wrote:
> This converts the if statement for dumping the stack into a
> WARN_ON in order to make this function's debugging check
> simpler and have a cleaner output when this condition
> occurs inside this function for when bugs related to
> adding a duplicate neighbour table timer arise.
> 
> Signed-off-by: Nicholas Krause <xerofoify@...il.com>
> ---
>  net/core/neighbour.c | 6 +-----
>  1 file changed, 1 insertion(+), 5 deletions(-)
> 
> diff --git a/net/core/neighbour.c b/net/core/neighbour.c
> index 3de6542..0bf71da 100644
> --- a/net/core/neighbour.c
> +++ b/net/core/neighbour.c
> @@ -165,11 +165,7 @@ static int neigh_forced_gc(struct neigh_table *tbl)
>  static void neigh_add_timer(struct neighbour *n, unsigned long when)
>  {
>  	neigh_hold(n);
> -	if (unlikely(mod_timer(&n->timer, when))) {
> -		printk("NEIGH: BUG, double timer add, state is %x\n",
> -		       n->nud_state);
> -		dump_stack();
> -	}
> +	WARN_ON(unlikely(mod_timer(&n->timer, when)));
>  }

NACK, please do not use WARN_ON for things with side effects.

--yoshfuji
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