[Vm-dev] Re: #ifCurtailed: multi-thread semantics
Ben Coman
btc at openinworld.com
Mon Feb 22 15:28:51 UTC 2016
On Mon, Feb 22, 2016 at 11:08 PM, Ben Coman <btc at openinworld.com> wrote:
> Just a curiousity. I learnt something new today...
> #ifCurtailed blocks are processed in the outer most thread.
>
> Transcript clear; crShow: Processor activeProcess; show:' - outside'.
> p1 :=
> [ [ Transcript crShow: Processor activeProcess; show: ' - inside'.
> 1 second wait.
> ] ifCurtailed: [ Transcript crShow: Processor activeProcess;
> show: ' - curtailed' . ]
> ] newProcess priority: 41.
> p1 resume.
> p1 terminate.
> ==>
> a Process(304957184) in nil - outside
> a Process(680396800) in nil - inside
> a Process(304957184) in nil - curtailed
>
> This makes some sense since (I guess) the inside thread is terminated
> before the curtailed block executes. However another curiousity...
>
> Transcript clear; crShow: Processor activeProcess; show:' - outside'.
> p1 :=
> [ Transcript crShow: Processor activeProcess; show: ' - middle'.
> p2 :=
> [ [ Transcript crShow: Processor activeProcess; show: ' - inside'.
> 1 second wait.
> ] ifCurtailed: [ Transcript crShow: Processor
> activeProcess; show: ' - curtailed' .
> 2 seconds wait ]
> ] fork.
> 3 second wait.
> ] newProcess priority: 41.
> p1 resume.
> p2 terminate.
> ==>
> a Process(304957184) in nil - outside
> a Process(146580480) in nil - middle
> a Process(417340928) in nil - inside
> a Process(304957184) in nil - curtailed
>
> ...why does the curtailed block execute in outside thread rather than
> the middle thread which still exists?
>
> Also interesting is that if the curtailed code contains a wait, it
> blocks the whole UI.
>
> cheers -ben
>
> btw, I added...
> Process>>printOn: aStream
> super printOn: aStream.
> aStream nextPutAll: '(' , self hash printString , ') in '.
> suspendedContext printOn: aStream
Further curiosity, the #ensure block is executed by the 'inner' process...
Transcript clear; crShow: Processor activeProcess; show:' - outside'.
p1 :=
[ [ Transcript crShow: Processor activeProcess; show: ' - inside'.
1 second wait.
] ensure: [ Transcript crShow: Processor activeProcess;
show: ' - curtailed' . ]
] newProcess priority: 41.
p1 resume.
p1 terminate.
==>
a Process(959980800) in nil - outside
a Process(636470784) in nil - inside
a Process(636470784) in nil - curtailed
And wrapping an #ensure: around an #ifCurtailed: makes its block be
executed by the 'inner' process...
Transcript clear; crShow: Processor activeProcess; show:' - outside'.
p1 :=
[ [ [ Transcript crShow: Processor activeProcess; show: ' - inside'.
1 second wait.
] ifCurtailed: [ Transcript crShow: Processor
activeProcess; show: ' - curtailed' ]
] ensure: [ Transcript crShow: Processor activeProcess;
show: ' - ensure' . ]
] newProcess priority: 41.
p1 resume.
p1 terminate.
==>
a Process(959980800) in nil - outside
a Process(663403776) in nil - inside
a Process(663403776) in nil - curtailed
a Process(663403776) in nil - ensure
BUT!!! Huh!?!?
The original example now has the curtailed block executed by the
'inside' process...
Transcript clear; crShow: Processor activeProcess; show:' - outside'.
p1 :=
[ [ Transcript crShow: Processor activeProcess; show: ' - inside'.
1 second wait.
] ifCurtailed: [ Transcript crShow: Processor activeProcess;
show: ' - curtailed' . ]
] newProcess priority: 41.
p1 resume.
p1 terminate.
==>
a Process(959980800) in nil - outside
a Process(329852416) in nil - inside
a Process(329852416) in nil - curtailed
cheers -ben
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