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

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

[YOSHIFUJI Hideaki/吉藤英明]

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@gmail.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

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

[Cong Wang]

On Mon, Jun 1, 2015 at 7:37 PM, YOSHIFUJI Hideaki/吉藤英明
<hideaki.yoshifuji@miraclelinux.com> wrote:
> 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@gmail.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.

Just:

int ret = mod_timer(...);
WARN_ON(ret);
...