lukechilds/node - node - Gitea: Git with a cup of tea

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Ryan aefbd57514 Add stack to promise.wait(). The problem was that if promise A was waiting and promise B was created and then also told to wait (from some callback coming off the event loop), and then promise A finished, promise B's wait would return. Promise A's wait would not return until promise B was finished. This is incorrect. To solve this issue properly, one probably needs to allocate separate execution stacks. I use, instead, Poor Man's Coroutines. We continue to use the main execution stack and force promises created most recently to return first. That is even if Promise A finishes first, neither wait() returns. Not until Promise B finishes, will its wait() return. After that is complete, Promise A's wait() will return. This introduces the problem of growing the "wait stack" infinitely. Thus I've added a strong warning to the documentation only to use this operation sparingly. require() and include() seem to be the proper use case for such a thing: they are called usually at program start up - they don't take too long to finish and they won't be called so often. Let's experiment with this stop-gap. If the infinite promise stack becomes a problem for many, then I will remove promise.wait() entirely or perhaps only use it for thread pool events.	15 years ago
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mjsunit	Add stack to promise.wait().	15 years ago

Ryan aefbd57514 Add stack to promise.wait().

The problem was that if promise A was waiting and promise B was created and
then also told to wait (from some callback coming off the event loop), and
then promise A finished, promise B's wait would return. Promise A's wait
would not return until promise B was finished. This is incorrect.

To solve this issue properly, one probably needs to allocate separate
execution stacks. I use, instead, Poor Man's Coroutines. We continue to use
the main execution stack and force promises created most recently to return
first.

That is even if Promise A finishes first, neither wait() returns. Not until
Promise B finishes, will its wait() return. After that is complete, Promise
A's wait() will return.

This introduces the problem of growing the "wait stack" infinitely. Thus
I've added a strong warning to the documentation only to use this operation
sparingly. require() and include() seem to be the proper use case for such a
thing: they are called usually at program start up - they don't take too
long to finish and they won't be called so often.

Let's experiment with this stop-gap. If the infinite promise stack becomes a
problem for many, then I will remove promise.wait() entirely or perhaps only
use it for thread pool events.

15 years ago

mjsunit

Add stack to promise.wait().

15 years ago