Re: BUG: fb_imageblit called before fb_check_var and fb_set_par function

[Knut Petersen <Knut_Petersen@t-online.de>]

Hi Antonino,

BTW: Thanks to Jochen Hein for testing cyblafb and reporting the
very long timeout after switching from X to console!

>> I never had expected that upon switching from X to a linux console
>> drawing functions like fb_imageblit would be called before the
>> fb_check_var and  fb_set_par functions have been called. But that´s
>> definitely the case.
>
> I'm surprised.  That was a problem in earlier versions of the kernel
> but I think that was fixed.  If you look at fbcon code, all calls to
> drawing functions:

My system is based on SuSE 9.2.
Kernel 2.6.13-rc7

1. If I do compile cyblafb as a module, there is no problem.

2. If I compile cyblafb into the kernel, there is no problem if
the first runlevel is 3 and I switch to runlevel 5 after login to
a console.

3. If I compile cyblafb into the kernel, the problem is 100% reproducible
if the first runlevel is 5. ps ax -H in that case:

1342 ?        Ss       0:00   /usr/sbin/cron
1352 ?        Ss       0:00   /usr/sbin/gpm -m /dev/ttyS0 -t ms
1362 ?        S        0:00   /opt/kde3/bin/kdm
1385 ?        S        0:20     /usr/X11R6/bin/X -nolisten tcp -br vt7 
-auth /var/lib/xdm/authdir/authfiles/A:0-Zgg52m
1392 ?        S        0:00     -:0             
1681 ?        S        0:00       /bin/sh /usr/X11R6/bin/kde
1716 ?        S        0:00         gpg-agent --daemon --no-detach 
--keep-display /bin/bash /etc/X11/xinit/xinitrc
1786 ?        S        0:00         kwrapper ksmserver
1648 ?        Ss       0:00   login -- root    
1744 tty1    Ss+    0:00     -bash
1649 tty2    Ss+    0:00   /sbin/mingetty tty2

The very first time I switch back from X to a linux console the bug
is triggered. cyblafb_sync() , called from cyblafb_imageblit(), times
out because mmio is switched off. Then a number of drawing functions
is called before the checkvar() and the setpar() are executed.

Let´s count in /var/log/messages .... exactly 64 calls.

64 (rows) * 16 (font height) = 1024 (screen height). I have not verified 
that
all those calls are imageblits, but  it seems that somebody wants to redraw
the screen.

After that the bug never triggers again.

I wonder why there should be a difference between kdm executed first
or login executed first, but that´s the case.

Feel free to send patches.

cu,
 Knut


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