Re: [Visualpython-users] gdisplay objects seldom work

[Roger F. <fe...@bi...>]

On Mon, 29 Sep 2003, Bruce Sherwood wrote:

> Jonathan Brandmeyer explained to me that there is a fundamental problem 
> with which I was unaware. Recent versions of the Unix/Linux kernel no 
> longer do "recursive" locking/unlocking of resources, something that 
> Visual has used. Jonathan has been working on eliminating the deadlocks 
> that can now occur and which may well be responsible for what you're 
> seeing. He's doing this in his experimental Boost-based version but 
> might retrofit the current Visual. This is not a problem on Windows.

Hi,
This problem looks like it is related to something I have noticed
on both Linux and Windows (98,2k,XP): gdisplay objects mostly work,
but occasionally they don't.
The result is a frozen window, usually displaying the minimum
axes possible (i.e. the problem seems to lie in the creation of the
window). 
In general, related activity in a display window will continue.
I guess that this is related to threading and some deadlock. I've
tried to trace through the code and find whereabouts the stall
is happening, but with little success - the usual problem with an
intermittent fault! However, some tests did seem to suggest that it got
lost between the exit from gdisplay's __init__ and the next call to the 
class instance.
One thing is that it does seem worse on machines that are a little tight 
on memory.
It is the one thing that does upset students a little with the visual 
package, otherwise they seem to like it.

Roger.

-- 
Roger Fearick
Dept. of Physics
University of Cape Town