linux-kernel - Re: [RFC PATCH] video/logo: introduce new system state for checking if logos are freed

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Date:	Tue, 26 May 2015 09:54:33 +0300
From:	Tomi Valkeinen <tomi.valkeinen@...com>
To:	<hs@...x.de>
CC:	<linux-kernel@...r.kernel.org>,
	Geert Uytterhoeven <geert@...ux-m68k.org>,
	<linux-fbdev@...r.kernel.org>,
	Jean-Christophe Plagniol-Villard <plagnioj@...osoft.com>
Subject: Re: [RFC PATCH] video/logo: introduce new system state for checking
 if logos are freed

On 26/05/15 06:56, Heiko Schocher wrote:

>> Without locking, the initmem may be freed while fb_find_logo() is
>> running.
> 
> Yes, you are right, that must be added ... but has such a change a
> chance to go in mainline?

I don't know. To be honest, this whole thing feels a bit like hackery. I
think initdata should only be accessed from initcalls, never asynchronously.

> BTW: Could this not be currently a problem on multicore systems?
> If lets say core 2 just draws the logo, another core 1 calls
> fb_logo_late_init() and later core 1 free_initmem(), while the core 2
> still draws it?

Yes, I think so...

So, maybe it would be better to not even try to go forward with the
current approach. Two approaches come to my mind:

1) Keep the logos in the memory, and don't even try to free them. I
don't know many bytes they are in total, though.

2) Make a copy of the logos to a kmalloced area at some early boot
stage. Then manually free the logos at some point (after the first
access to the logos? after a certain time (urgh...)?).

 Tomi

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