linux-kernel - Re: LOCALVERSION_AUTO considered harmful

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Message-ID: <33355.71.245.98.113.1271040992.squirrel@www.xenotime.net>
Date:	Sun, 11 Apr 2010 19:56:32 -0700 (PDT)
From:	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 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?

---
~Randy

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