Message-ID: <435FEF26.4050902@t-online.de>
Date: Wed, 26 Oct 2005 23:03:34 +0200
From: Knut Petersen <Knut_Petersen@t-online.de>
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To: alessandro.suardi@gmail.com
CC: airlied@gmail.com, linux-kernel@vger.kernel.org
Subject: Re: X unkillable in R state sometimes on startx , /proc/sysrq-trigger
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Two months ago I started a thread

    BUG: fb_imageblit called before fb_check_var and fb_set_par function

in the Linux-fbdev-devel mailing list. I found that the accelerated 
imageblit
function of a framebuffer driver might be called before the graphics 
engine is
initialized ... normally that happens in the fb_set_par function. For 
cyblafb
I solved the problem by extending the fb_sync function to include a call 
to the
graphics engine init function after a short timeout, but the problem is 
still
present in all recent kernels. It might be argued that this is not a 
kernel bug
but a problem of  X - have a look at the Linux-fbdevel thread.

Does X start reliably without a linux framebuffer driver?
Does X start reliably with vesafb?

If the answer is "yes", then have a look at the radeonfb sync function.
After a short timeout, assume that an erroneous X driver disabled mmio,
so (re)enable mmio  and (re)init the graphics engine.

cu,
 knut

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