Forward progress guarantees for Jobs

[lars-t-hansen]

The spec draft currently adds a weak forward progress guarantee for ES6 jobs.

The guarantee should be strengthened, and it can be done so in the same manner as in C++. For the latter, see this paper.

[lars-t-hansen]

A proposal in the HTML spec (allow workers to be created with specific guarantees about forward progress, in order to allow resource management) pertains to this: whatwg/html#851.

[lars-t-hansen]

Updated the spec language slightly to account for agents with shared execution threads.

[lars-t-hansen]

The section on lock-freedom now contains a note contrasting it to wait-freedom (though it does not take that any further).

[jfbastien]

Circling back, the following was added to C++17: http://wg21.link/p0296r2

[jfbastien]

@lars-t-hansen do you believe this has been addressed? In #5 (comment) you said:

Once the spec goes to TC39 it will become natural to file the missing forward progress guarantee as a bug against ES262.

Now that we're at Stage 4, is this something that needs to be addressed?

[lars-t-hansen]

@jfbastien, thanks for picking up this thread again. cc @syg.

The current spec language is here: https://tc39.github.io/ecma262/#sec-forward-progress. That language is indicative of the intent but informal compared to C++ and probably hasn't changed very much since the present issue was filed.

I don't feel great urgency to strengthen it further since, unlike C++, we have a largely operational semantics and can talk about "making a step" in the semantics as making forward progress, but do argue the point if you disagree.

[lars-t-hansen]

I'll take the thumbs-up as a sign that we're done here.