Re: [AD] Feedback about 3.9.28 for linux

[Shawn Hargreaves <shawn@xxxxxxxxxx>]

Grzegorz Adam Hankiewicz <gradha@xxxxxxxxxx> writes:
> Finally! I think I know what's my problem. After chopping off the mouse
> example, I discovered that it's not the mouse but the timers which locks 
> my computer.

That makes sense, based on your list of programs that crash.

Is this new in 3.9.28, or an ongoing problem? Beause I fixed a couple of 
time-loss bugs in this version, and altered how the time behaves during a 
mode switch. I don't see how that could have broken anything, but if this is 
a new problem, it is almost certainly the culprit.

> Now, after reading some of the code, I think that this is related with the
> fact that I don't have that vsync patch for the matrox framebuffer. Shawn,
> could you email it to me again, please?

Whoah! I just wrote a long explanation of why this couldn't be the problem, 
but actually, I think you may well be exactly right. The bug is in Allegro, 
though, so I won't let you have that patch until we've managed to fix it 
some other way :-)

Consider this sequence of events:

- switch away from Allegro
- Allegro saves the current palette
- Allegro suspends the timer
- do other stuff
- switch back to Allegro 
- Allegro restores the palette
- this involves waiting for a retrace
- Allegro notices that your fbcon has no vsync support
- it notices the timer module is installed, so decides to use that instead
- it starts waiting for retrace_count to be incremented
- but the timer is suspended, so this never happens

What happens if in fbcon.c, you change take out the code:

   /* bodged implementation for when the framebuffer doesn't support it */
   if (_timer_installed) {
      prev = retrace_count;

      do {
      } while (retrace_count == prev);
   }

from the end of the fb_vsync() function?

> BTW, so much talk, and I still don't know if it's really correct to say 
> "my computer hanged up", or something like that. What's the "cientific" 
> term? :-) 

I'd probably say "hanged" or "locked up", because "hanged up" makes me think 
more of hanging up the receiver at the end of a phone call...

But strictly speaking, I don't think any of these terms are right. When this 
happens, the correct response is to invent a new phrase specifically for 
that occassion: the only rules are that it should be lengthy, amusing, and 
contain at least 42 obscene words :-)


--
Shawn Hargreaves - shawn@xxxxxxxxxx - http://www.talula.demon.co.uk/
"A binary is barely software: it's more like hardware on a floppy disk."