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Date: Wed, 27 Nov 2013 11:45:17 +0100 (CET)
From: Thomas Gleixner <tglx@linutronix.de>
To: Pablo Neira Ayuso <pablo@netfilter.org>
cc: Sasha Levin <sasha.levin@oracle.com>, Patrick McHardy <kaber@trash.net>,
        kadlec@blackhole.kfki.hu, "David S. Miller" <davem@davemloft.net>,
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        Christoph Lameter <cl@linux-foundation.org>, Greg KH <greg@kroah.com>,
        Russell King <linux@arm.linux.org.uk>
Subject: Re: netfilter: active obj WARN when cleaning up
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On Wed, 27 Nov 2013, Pablo Neira Ayuso wrote:

> On Tue, Nov 26, 2013 at 02:11:57PM -0500, Sasha Levin wrote:
> > Ping? I still see this warning.
> 
> Did your test include patch 0c3c6c00c6?

And how is that patch supposed to help?
 
> > >[  418.312449] WARNING: CPU: 6 PID: 4178 at lib/debugobjects.c:260 debug_print_object+0x8d/0xb0()
> > >[  418.313243] ODEBUG: free active (active state 0) object type: timer_list hint:
> > >delayed_work_timer_fn+0x0/0x20

> > >[  418.321101]  [<ffffffff812874d7>] kmem_cache_free+0x197/0x340
> > >[  418.321101]  [<ffffffff81249e76>] kmem_cache_destroy+0x86/0xe0
> > >[  418.321101]  [<ffffffff83d5d681>] nf_conntrack_cleanup_net_list+0x131/0x170

The debug code detects an active timer, which itself is part of a
delayed work struct. The call comes from kmem_cache_destroy().

         kmem_cache_free(kmem_cache, s);

So debug object says: s contains an active timer. s is the kmem_cache
which is destroyed from nf_conntrack_cleanup_net_list.

Now struct kmem_cache has in case of SLUB:

    struct kobject kobj;    /* For sysfs */

and struct kobject has:

#ifdef CONFIG_DEBUG_KOBJECT_RELEASE
    struct delayed_work     release;
#endif

So this is the thing you want to look at:

commit c817a67ec (kobject: delayed kobject release: help find buggy
drivers) added that delayed work thing.

I fear that does not work for kobjects which are embedded into
something else.

Handing off to rmk, mm and kobject folks.

Thanks,

	tglx