linux-kernel - Re: Linux kernel : sysctl registering table under same proc name (path) gives warning and call trace while unregistering

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Date:	Thu, 08 Mar 2012 13:12:10 -0800
From:	ebiederm@...ssion.com (Eric W. Biederman)
To:	chaitanya g <chaitanyag3.14@...il.com>
Cc:	linux-kernel@...r.kernel.org
Subject: Re: Linux kernel : sysctl registering table under same proc name (path) gives warning and call trace while unregistering

chaitanya g <chaitanyag3.14@...il.com> writes:

> Hello there,
>
> I am creating a sysctl kernel module to register 2 hierarchy under
> same proc name. For e.g.
>
>   my_net
>   |          |
> net1  net2
>  |         |
> t1        t2
>
> So, I used register_sysctl_paths() API. Everything works fine when
> registering the sysctl tables net1 net2 under path name my_net.
>
> Problem is when unregistering the tables dmesg shows kernel tainted
> warning and a call trace.
>
> Here, is pastebin link to the warning message http://pastebin.com/NfLQhikJ
>
> Here is pastebin link to module source http://pastebin.com/jSfPW5Y5

Adding those as attachments or simple inline inclusions would have been
much easier to work with.

> Kindly, please help me to resolve this panic.

Well it wasn't a panic, it was a WARN_ON, and you are running against a
very old kernel.  The .ctl_name field no longer exists.  I guess it says
2.6.32.something.

The only possibility is you have run afoul of the current sysctl rule
that you must create a sysctl path before you add child entries and you
must destroy a sysctl path before you remove child entries.  It is
extremely non-intuitive, and should be fixed in my current sysctl tree.

Eric
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