On Tue, Jun 19, 2007 at 03:54:52PM +0200, Bodo Eggert wrote:
> Does the FLUSH DTRT by design, or does it just shrink and hide the original
> race?
I haven't deeply studied this aspect of the source, don't know what
_exactly_ this FLUSH does, but of course I have an inner feeling about this.
Kind of this macro does the _real_ print on the screen. It actually calls
vc->vc_sw->con_putcs, whereas I guess vc_sw refers to the particular
implementation (vga, fb) and con_putcs might be doing the real job.
Without these two new FLUSHes the behavior was very funny: applications
(e.g. text editors) highlighed incorrect cells, but either switching between
VTs, or gpming over these cells corrected the display. So the logical
content behind the scenes (reflected by /dev/vcsa*) was maintained
correctly, the bug is somewhere when the content is first displayed.
I saw that this FLUSH was already used 3 times inside do_con_write(), I
placed it here 2 more times (when changing color attr to inverse and when
reverting to normal). I think it cannot hurt, and apparently it fixes the
problem.
But you may be right: yes, it might be a bug (or misfeature) in the FB code,
too. Could you please look after it? I don't think I'd be able to do it and
have time for this.
> And why wasn't VGA affected, too?
I guess tt must be some difference between the actual VGA and FB code that
is called from here. I don't know whether it's a bug in FB or just some
difference.
Perhaps it's that the FB driver's con_putcs() call uses vc->vc_attr (the
current attr for the console) for each char cell to be printed, instead of
the own attr values of the cells themselves. Just an idea...
--
Egmont
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