netdev - Re: [RFC][PATCH] Fix another namespace issue with devices assigned to classes

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Message-ID: <AANLkTikB0Amzi61JLxdY5HL-2s_nbYo3JH8vXooXzHdQ@mail.gmail.com>
Date:	Tue, 8 Jun 2010 16:21:24 +0200
From:	Kay Sievers <kay.sievers@...y.org>
To:	Johannes Berg <johannes@...solutions.net>
Cc:	"Eric W. Biederman" <ebiederm@...ssion.com>,
	Greg KH <greg@...ah.com>, netdev <netdev@...r.kernel.org>
Subject: Re: [RFC][PATCH] Fix another namespace issue with devices assigned to 
	classes

On Tue, Jun 8, 2010 at 16:06, Johannes Berg <johannes@...solutions.net> wrote:
> On Tue, 2010-06-08 at 15:54 +0200, Kay Sievers wrote:
>> On Tue, Jun 8, 2010 at 14:03, Johannes Berg <johannes@...solutions.net> wrote:
>> > On Tue, 2010-06-08 at 13:55 +0200, Kay Sievers wrote:
>> >
>> >> Ok, this needs testing.
>> >>
>> >> Please let me know, if that works for you so far.
>> >
>> > Will do. Just a question: none of this seems to pin the module? So can I
>> > be sure if I rmmod the module that the release function will still be
>> > around etc.?
>>
>> Oh, sorry, that's something very specific to network devices, that the
>> module can be unloaded while the devices it has created are still in
>> use. I am not sure right now what's needed to make this work in a
>> single module.
>
> Well they will be unregistered and everything, but once all the netdevs
> are gone etc. the devices you create in the patch might stick around
> because somebody has them open in sysfs, and I see nothing that would
> pin the module in that case?

That's what I mean, I have no idea how to solve that with network
devices. I don't think any other subsytem allows to unload the module,
when devices, the module has created, are in use.

With this patch, it is likely to fail, even without sysfs, just when
the netif is still in up, and the module is unloaded.

The current code uses the in-core class_create() logic, which was only
meant for devices with a device node, and which is cleaned up by the
core itself. That's why this issue never appeared before.

But as said, I have no idea how to solve that with a single module. It
might not work at all without moving stuff into the core. That people
use device_create() with no major/minor might indicate that something
else is needed here. :)

Kay
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