[Stackless] Stackless 2.6.2/Win crash with very short script

[Richard Tew]

Sorry, by frame going away, I meant the exiting of the function call
which frees its locals including the channel.

2009/8/9 Kristján Valur Jónsson <kristjan at ccpgames.com>:
> Richard, I don't think this is it at all.  Blocking doesn't cause the frame to go away, and the frame doesn't get collected before the error occurrs.
> I think it is a simple malfunction in the soft-switching code.  The issue goes away if soft-switching is turned off.
> I'll have another go at it.
>
>> -----Original Message-----
>> From: Richard Tew [mailto:richard.m.tew at gmail.com]
>> Sent: 9. ágúst 2009 04:42
>> To: Kristján Valur Jónsson
>> Cc: Stefan Reich; stackless at stackless.com
>> Subject: Re: [Stackless] Stackless 2.6.2/Win crash with very short
>> script
>>
>> 2009/8/8 Kristján Valur Jónsson <kristjan at ccpgames.com>:
>> > I had a go at this today.
>> > It is a bug with soft-switching.  turning off soft switching makes
>> the problem go away.
>> > The issue happens when the tasklet blocks and the sheduler is
>> reviving main.  It decides to try soft switching but then inserts the
>> hard switching frame.  This is how far I got.
>> >
>> > Richard, I am very unfamiliar with soft switching so maybe you can
>> help me out with this in a private thread?
>>
>> This is the old problem I fixed years ago approaching from a different
>> angle.  It looks like some other change we have made has broken it in
>> a different way.  We should be hesitant we don't break something else
>> when we fix this.
>>
>> I don't have time to look further into this right now, especially
>> given that it is not a realistic use case that someone would encounter
>> in a deployed application.
>>
>> But my understanding of it is that a tasklet blocks on a channel that
>> was created within it.  This soft switches and the tasklet function
>> exits, causing garbage collection of the channel (because tasklets do
>> not hold references to channels they block on and the only reference
>> to the channel is the frame).  The garbage collection of the channel
>> with the only reference to the tasklet within it, means the tasklet is
>> also garbage collected.  So of course we hard switch to the tasklet,
>> despite the fact we are still effectively in it.
>>
>> I don't see an obvious fix to this.
>>
>> Cheers,
>> Richard.
>
>