linux-kernel - Re: [PATCH 1/12] i386: Distinguish absolute symbols

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Date:	Mon, 09 Oct 2006 09:35:26 +0200
From:	Gerd Hoffmann <kraxel@...e.de>
To:	vgoyal@...ibm.com
Cc:	Andrew Morton <akpm@...l.org>,
	linux kernel mailing list <linux-kernel@...r.kernel.org>,
	Reloc Kernel List <fastboot@...ts.osdl.org>,
	ebiederm@...ssion.com, ak@...e.de, horms@...ge.net.au,
	lace@...kratochvil.net, hpa@...or.com, magnus.damm@...il.com,
	lwang@...hat.com, dzickus@...hat.com, maneesh@...ibm.com
Subject: Re: [PATCH 1/12] i386: Distinguish absolute symbols

>> looks odd.  What's the point in putting a gap before __smp_alt_end?  Moving
>> __smp_alt_end to before the ALIGN doesn't prevent the warning.
>>

> Please find attached a patch for the same. I am also copying Gerd Hoffmann,
> who introduced this ALIGN. Gerd, can you please confirm that above ALIGN()
> is not required and the patch attached should be fine.

The data between __smp_alt_start and __smp_alt_end will be released at
boot time in some cases (UP machine, kernel without CPU_HOTPLUG, ...).

Releasing memory works at page granularity only, thats why I added the
alignment.  I think you can't simply drop it.

> o There seems to be one extra ALIGN(4096) before symbol __smp_alt_end. The
>   only usage of __smp_alt_end is to mark the end of smp alternative
>   sections so that this memory can be freed. As a physical page is freed
>   one has to just make sure that there is no other data on the same page
>   where __smp_alt_end is pointing. There is already a ALIGN(4096) after
>   this section which should take care of the above issue. Hence it looks
>   like the ALIGN(4096) before __smp_alt_end is redundant and not required.

Hmm, ok, it should work then.  How about adding a comment to make sure
the align after __smp_alt_end doesn't get dropped by accident?

cheers,

  Gerd

-- 
Gerd Hoffmann <kraxel@...e.de>
http://www.suse.de/~kraxel/julika-dora.jpeg
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