[Lazarus] lazbuild 100% CPU-Power

[Thomas Moritz]

Hi!

I got the same when doing some classes for my project. My solution is add a
TEvent in my thread that will be signaled in the last line of the thread
loop.

On my application instead use TThread.WaitFor, I use TThread.MyWaitFor that
internals do:

While TEvent.WaitFor(1)<>wrSignaled do
   Application.ProcessMessages;

It solves my problem with threads finalization on windows and linux.


Fabio

2010/10/8 Graeme Geldenhuys <graemeg.lists at gmail.com>

> Hi,
>
> [Just as well the Lazarus IDE didn't get the thread update mentioned a
> few days ago... where a thread was doing work, and the main thread was
> waiting for that thread to finish... it wouldn't have worked under
> Linux it seems.]
>
>
> I just stumbled across this issue in fpGUI, and I see MSEgui and
> LCL-GTK2 has the
> exact same problem. See attached project. I haven't tried LCL-QT, but I
> presume
> that same issue will persist.
>
> A simple program (just for illustrative purposes), where a thread
> updates the progress bar (the thread could be doing any long running
> process).
> Click the button, it creates a thread and
> starts it off. If then waits for the thread to finish, then displays
> that it has finished in the GUI, and free's the thread manually.
>
> If you use the MyThread.WaitFor to wait for the thread to finish, then
> the application is instantly frozen (even the thread), nothing gets
> updated and you have to kill the process. For some reason
> WaitFor blocks the main thread's event loop. It seems this issue is
> only under FPC apps and under X11 (no matter the GUI toolkit),
> it works fine under Windows.
>
> The work around, is to use a boolean variable in the thread class, and
> a while loop which checks if the boolean variable is true, if not it
> calls Application.ProcessMessages (to keep the app alive).
>
> Like I said, this is a stupid example, but it illustrates that WaitFor
> cannot be used under X11 (for our GUI toolkits). Any ideas as to why
> WaitFor blocks the main event loop? Is it a Linux thing, X11 thing, or
> just that we made a mistake somewhere?
>
> So what is wrong? Is it the TThread.WaitFor implementation that is
> flawed? Is it X11 that is flawed, or just GUI toolkit developers that
> don't know how to code (thought I doubt it's the latter). :)
>
> As an experiment (I'm all out of ideas now), I dived into the
> TThread.WaitFor implemenation, as saw that it calls
> WaitForThreadTerminate() with no timeout value. I though, well, let me
> try calling WaitForThreadTerminate() directly with say a 2 second
> timeout. No luck there. The instant you call that, the application is
> frozen. It never times out either, so the FPC+Unix
> WaitForThreadTerminate() functions seems broken too. :-/
>
> I guess I need to file a FPC bug report about WaitForThreadTerminate()
> being broken under Linux, but I wanted others to confirm this first,
> before I do.
>
> Did anybody know about this? Anybody know how we can get
> TThread.WaitFor to actually work under Linux/Unix?
>
>
> --
> Regards,
>  - Graeme -
>
>
> _______________________________________________
> fpGUI - a cross-platform Free Pascal GUI toolkit
> http://opensoft.homeip.net:8080/fpgui/
>
> --
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