Can strict ST break referential transparency?

Yuras Shumovich shumovichy at
Thu Nov 23 16:11:37 UTC 2017

So my theory is correct, but it is already fixed in 8.2. Nice!

Thank you for clarification!


23-11-2017, Чцв а 10:20 -0500, Ben Gamari напісаў:
> Yuras Shumovich <shumovichy at> writes:
> > Hello,
> > 
> Hello,
> Sorry for the late reply; this required a bit of reflection. The
> invariants surrounding the suspension of ST computations is a rather
> delicate and poorly documented area.
> I believe the asynchronous exception case which you point out is
> precisely #13615. The solution there was, as David suggests, ensure
> that
> no resulting thunk could be entered more than once by a very strict
> blackholing protocol. Note that this isn't normal "eager" blackholing
> protocol, which still might allow multiple entrancy. It's rather a
> more
> strict variant, requiring two atomic operations.
> I can't be certain that there aren't more cases like this, but I
> suspect
> not since most asynchronous suspensions where the resulting thunk
> might
> "leak" back into the program go through the raiseAsync codepath that
> was
> fixed in #13615.
> Cheers,
> - ben

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