linux-kernel - Re: [PATCH] kref: add function for reading kref value

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Date:	Mon, 12 Dec 2011 17:39:12 +0200
From:	Daniel Baluta <daniel.baluta@...il.com>
To:	Eric Dumazet <eric.dumazet@...il.com>
Cc:	Greg KH <greg@...ah.com>, linux-kernel@...r.kernel.org,
	netdev@...r.kernel.org, adobriyan@...il.com
Subject: Re: [PATCH] kref: add function for reading kref value

On Mon, Dec 12, 2011 at 5:32 PM, Eric Dumazet <eric.dumazet@...il.com> wrote:
> Le lundi 12 décembre 2011 à 17:21 +0200, Daniel Baluta a écrit :
>> On Mon, Dec 12, 2011 at 5:02 PM, Greg KH <greg@...ah.com> wrote:
>> > On Mon, Dec 12, 2011 at 02:44:52PM +0200, Daniel Baluta wrote:
>> >> We can easily get kref refcount value by accesing
>> >> kref->refcount but it is better to have a function
>> >> for this.
>> >
>> > No, you should NEVER need the value of the kref, if you do, you are
>> > doing something wrong.
>> >
>> > What code needs this patch?
>>
>> I plan to replace raw refcount patterns from net/ with kref, and
>> I have noticed that there are some parts of code who need access
>> to kref->refcount value.
>>
>> e.g:
>>
>> core/neighbour.c:152:                 if (atomic_read(&n->refcnt) == 1 &&
>> core/neighbour.c:801:                 if (atomic_read(&n->refcnt) == 1 &&
>> sched/cls_u32.c:459:  if (ht->refcnt == 1) {
>>
>
> Well, its not a good idea.
>
> kref adds nothing here.
>

Ok, for the moment it seems to be a bad idea. But my intention is
to integrate kref to networking code, and then to write a general
debugging tool for refs.

Tracking down reference count problems is hard, and this tool can
really help everyone.

thanks,
Daniel.
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