Re: [Hecl-devel] Issue with synchronized eval

[Wolfgang S. K. <wol...@da...>]

David Welton wrote:
> The synchronized eval appears to cause some problems for http.geturl.
> I'm investigating...
> 

I spent some time on the synchronized problem and it appears to be more
complex on j2me devices than I expected.
Let's look at the following scenario:

script performing (sketch):

proc timer {} {
	puts timer
	after 1000 timer
}

proc main {} {
	timer
	while 1 {
		set start [clock time]
		http.geturl http://www.x.org
		puts "http: [- [clock time] $start]s";
	}
}

main

I expect the timer to fire every second, even when the http connection
waits for an answer from the server. The current implemetation yields
the expected result, but the http-call takes more time than expected on
j2me devices. The problem seems to be in the implementation of
doOneEvent, but I need to spend more time on the issue.

One option that came into my mind is to make the interpreter save to be
called from multiple threads, but this would require the evaluation
stack to be passed down explictly, so we have

protected interp.eval(Thing,CallStack)
public interp.eval(Thing)

Hecl will use the internal first method whereas external callers use the
latter. Unfortunately this approach requires all command implementations
in Java to have the stack as additional calling parameter as well :-(
Since this is a major change, I will look for other solutions first.

Remind: On j2se, the problem does not occur. I guess thread handling and
synchronization is done quite different in j2me. Does anybody have
experience with the behavior on android?

-- 
Wolfgang Kechel                     mailto:wol...@da...
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