linux-kernel - Re: LOCALVERSION_AUTO considered harmful

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Message-ID: <4BC2984D.2050102@xenotime.net>
Date:	Sun, 11 Apr 2010 20:49:33 -0700
From:	Randy Dunlap <rdunlap@...otime.net>
To:	Thomas Gleixner <tglx@...utronix.de>
CC:	Pavel Machek <pavel@....cz>,
	Geert Uytterhoeven <geert@...ux-m68k.org>,
	Alexey Dobriyan <adobriyan@...il.com>,
	kernel list <linux-kernel@...r.kernel.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Andrew Morton <akpm@...l.org>
Subject: Re: LOCALVERSION_AUTO considered harmful

On 04/11/10 19:56, rdunlap@...otime.net wrote:
> On Sun, April 11, 2010 3:24 pm, Thomas Gleixner wrote:
>> On Sun, 11 Apr 2010, Pavel Machek wrote:
>>
>>
>>> On Sun 2010-04-11 20:58:58, Geert Uytterhoeven wrote:
>>>
>>>> On Mon, Apr 12, 2010 at 20:51, Alexey Dobriyan <adobriyan@...il.com>
>>>> wrote:
>>>>
>>>>> On Sun, Apr 11, 2010 at 06:47:01PM +0200, Pavel Machek wrote:
>>>>>
>>>>>> @@ -99,6 +98,11 @@ config LOCALVERSION_AUTO
>>>>>>         appended after any matching localversion* files, and after
>>>>>> the value         set in CONFIG_LOCALVERSION.
>>>>>>
>>>>>>
>>>>>> +       Unfortunately, such finegrained versioning will mean that
>>>>>> you will +       not be able to use modules for development; even
>>>>>> "make modules"
>>>>>> +       will change module versions, making recompiled modules
>>>>>> impossible +       to insert into old kernel.
>>>>>>
>>>>>
>>>>> That's conditional BS.
>>>>> Turn off CONFIG_MODVERSIONS already.
>>>>>
>>>>
>>>> Yeah, I disabled it ages ago. Even then (before git, probably even
>>>> before bitkeeper) I had hard times inserting modules...
>>>>
>>>
>>> I _had_ it off
>>>
>>>
>>> # CONFIG_MODVERSIONS is not set
>>>
>>>
>>> It seems some checking survives CONFIG_MODVERSIONS unset and that
>>> checking is strict enough to refuse module load after one "make modules"
>>> with LOCALVERSION_AUTO on...
>>
>> So instead of fixing the CONFIG_MODVERSIONS=n case you go the easy way
>> of killing LOCALVERSION_AUTO ? Brilliant.
> 
> Pavel's original example (afaik) was on April 5:
> Subject: 2.6.34-rc3: Can't insmod after make, because versions now differ?!
> 
> Apr  5 07:33:16 amd kernel: udlfb: version magic
> '2.6.34-rc3-00345-ge8240f9-dirty SMP mod_unload CORE2 ' should be
> '2.6.34-rc3-00344-g548fc0a-dirty SMP mod_unload CORE2 '
> 
> 
> So what do you suggest?  If the "magic" strings contain "-dirty ",
> then ignore that and the 2 preceding hyphen-separated fields?
> 
> That could be dangerous if some kernel internal structures have changed.
> I.e., user/developer beware.
> 
> Maybe ignore those strings iff some override has been set somewhere?

Pavel, does "modprobe --force" work?

-- 
~Randy
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