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Subject: Re: [PATCH] kref: add function for reading kref value
From: Eric Dumazet <eric.dumazet@gmail.com>
To: Daniel Baluta <dbaluta@ixiacom.com>
Cc: Greg KH <greg@kroah.com>, linux-kernel@vger.kernel.org,
        netdev@vger.kernel.org, adobriyan@gmail.com
Date: Mon, 12 Dec 2011 18:42:34 +0100
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Le lundi 12 décembre 2011 à 18:42 +0200, Daniel Baluta a écrit :

> Yes, but you have to do this each time you start debugging, for a
> particular referenced counted object.
> 

What a big deal.

> We must find a clever solution to avoid the noise. (e.g use
> /proc, /sysfs, /debugfs options to trigger dumping info for
> some/all objects with a certain state).
> 
> Usecase:
> 
> At some point we need to know all objects with refcount X,
> and their history of get/put operations.
> 
> For us it would have been very useful when debugging dev
> refcnts problems. With the current implementation kernel
> only dumped info at dev.c:5429:
> 

current on your git repo maybe, not on ours :(

> printk(KERN_EMERG "unregister_netdevice: "
>        waiting for %s to become free. Usage "
>        count = %d\n",
>        dev->name, atomic_read(&dev->refcnt));
> 

This is a very good example where you _cannot_ use kref, since we now
use a percpu refcnt fot netdevice.