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	<d555a1ae7e1735204d7ee20381034260@terzarima.net>
From: Venkatesh Srinivas <me@acm.jhu.edu>
Date: Thu, 28 Oct 2010 15:24:58 -0400
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To: Fans of the OS Plan 9 from Bell Labs <9fans@9fans.net>
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Subject: Re: [9fans] A little more ado about async Tclunk
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On Thu, Oct 28, 2010 at 8:12 AM, Charles Forsyth <forsyth@terzarima.net>wrote:

> you're essentially replacing
>        f := open(name, ...)
>        ...
>        close(f)
>
> which runs as a sequential process, and subject to the usual rules for
> sequential
> composition, by
>
>        f := open(name, ...)
>        ...
>        spawn clunk(f)
>
> which introduces a race with an invisible anonymous process with no means
> of synchronisation.
>
> what could possibly go wrong with that?
>
> (actually, it's more complex than spawning a new process, but the added
> complexity of a set of service processes changes the details but not the
> existence of the race, and doesn't affect the anonymity.)
>

Hmm, I don't see the race there; perhaps I'm missing something or being
blind; could you explain?

Also, if that is racy, isn't this at least analogous?

f := Sys->open(name, ...);
... # put f in a cyclic structure
f = nil;
evil_cyclic = nil;
... # wait until an invisible service process closes it, perhaps later?

Thanks,
-- vs

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On Thu, Oct 28, 2010 at 8:12 AM, Charles Forsyth <span dir=3D"ltr">&lt;<a h=
ref=3D"mailto:forsyth@terzarima.net">forsyth@terzarima.net</a>&gt;</span> w=
rote:<br><div class=3D"gmail_quote"><blockquote class=3D"gmail_quote" style=
=3D"margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex;">

you&#39;re essentially replacing<br>
 =C2=A0 =C2=A0 =C2=A0 =C2=A0f :=3D open(name, ...)<br>
 =C2=A0 =C2=A0 =C2=A0 =C2=A0...<br>
 =C2=A0 =C2=A0 =C2=A0 =C2=A0close(f)<br>
<br>
which runs as a sequential process, and subject to the usual rules for sequ=
ential<br>
composition, by<br>
<br>
 =C2=A0 =C2=A0 =C2=A0 =C2=A0f :=3D open(name, ...)<br>
 =C2=A0 =C2=A0 =C2=A0 =C2=A0...<br>
 =C2=A0 =C2=A0 =C2=A0 =C2=A0spawn clunk(f)<br>
<br>
which introduces a race with an invisible anonymous process with no means o=
f synchronisation.<br>
<br>
what could possibly go wrong with that?<br>
<br>
(actually, it&#39;s more complex than spawning a new process, but the added=
 complexity of a set of service processes changes the details but not the e=
xistence of the race, and doesn&#39;t affect the anonymity.)<br></blockquot=
e>

<div><br></div><div>Hmm, I don&#39;t see the race there; perhaps I&#39;m mi=
ssing something or being blind; could you explain?</div><div><br></div><div=
>Also, if that is racy, isn&#39;t this at least analogous?</div><div><br>

</div><div>f :=3D Sys-&gt;open(name, ...);</div><div>... # put f in a cycli=
c structure</div><div>f =3D nil;</div><div>evil_cyclic =3D nil;</div><div>.=
.. # wait until an invisible service process closes it, perhaps later?</div=
>
<div>
<br></div><div>Thanks,</div></div><div>-- vs</div>

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