[Stackless] [threading] Stackless based replacement

David Naylor dragonsa at highveldmail.co.za
Fri Sep 26 15:50:09 CEST 2008

On Friday 26 September 2008 15:11:00 Jeff Senn wrote:
> On Sep 26, 2008, at 8:04 AM, David Naylor wrote:
> > Just a few questions:
> > 1) Under what conditions does atomic not work?
> Hm.  I thought you meant *your* atomic didn't work.  We should really
> be worried
> (well, me, at least!) if .set_atomic doesn't work!   Can you generate
> a test case?

My atomic is based on .set_atomic, and there should not be any explicit 
passing of control.  I compensated for it [the apparent bug?] by forcing a 
reschedule until the correct tasklet came about...

Unfortunately my code that generates this problem is FreeBSD based and will 
only work with FreeBSD Ports (If you have I will gladly send you the code).  

> [I didn't look at all your code carefully... it's not clear to me how/
> if you are
> doing automatic scheduling.  ...Oh... Did you read
> carefully?  .set_atomic does
> only stop *automatic* switching of control... explicit passes (e.g.
> send) can
> still "switch" tasklets...]

I didn't read that carefully, but it should not be a problem.  Yes I am using 
automatic scheduling (with run(1000))

> > 2) Will stackless switch to another tasklet when entering blocking
> > routines
> > (like IO), I know threads do this...
> No it won't.  In fact, it fundamentally *can't* (since it "runs" in
> only one thread).

Surely there is a way around this?  Some kind of pooling select?  If there is 
no work around then I cannot see too much practical use for my thread library 
[except having to avoid learning tasklets for someone who is familiar with 
threads].  As I understand it, due to the GIL the only real practical use for 
threads is if one has blocking function calls (IO-type, etc)

[Has the GIL restriction been fixed in 3k?  As far as I know Jython does not 
have this limitation...]

> > 3) Does anyone know where to find how many commands python processes
> > before it
> > tries to switch threads (I remember something like that happening?)
> It's not really "commands"... more like a number of loops through the
> code interpreter.
> Did you mean "threads" or "tasklets"?


> If you meant "threads" the answer is complicated... if you meant
> "tasklets"
> then see the parameter to stackless.run.

I asked because I remember somewhere that python does a 'switch' every X 
lines...  I just wanted to pass the same number to run().  

> print stackless.run.__doc__
> -Jas


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