983692 - PJS: Rewrite testing mechanism to use magic globals rather than magic parameters

Status: RESOLVED WONTFIX

(Core :: JavaScript Engine, defect)

Description

[Niko Matsakis [:nmatsakis]]

To make reproducible tests, we need to be able to run things like `mapPar` in distinct modes (force parallel, etc). Unfortunately, the mechanism we used for this was to pass an extra argument. This means it's available to end users, which is bad. I think the right mechanism, though it's a bit hacky, is to have some global variable in ForkJoin.cpp (or in the context, maybe) storing the current mode, and expose some functions in TestingFunctions.cpp for modifying this value. This way we can be sure that in production firefox the mode is never changed. It also avoids us having to figure out how to thread mode arguments everywhere and makes writing the tests more reliable (if you neglect to thread the mode, the various helpers like `assertParallelExecSucceeds` don't work).

Comment 1

[Niko Matsakis [:nmatsakis]]

Note: we might also want to disable work stealing in some exec modes. In particular, it can hide bugs if one thread (e.g., the main thread) steals all the work.

Comment 2

[Niko Matsakis [:nmatsakis]]

(And has actively done so already, though I can't be bothered to fish up the bug # right now)

Comment 3

[Niko Matsakis [:nmatsakis]]

Attachment: Bug983686.diff

This seems to work via manual inspection.

Comment 4

[Niko Matsakis [:nmatsakis]]

Comment on attachment 8391278 [details] [diff] [review]
Bug983686.diff

Attached to wrong bug :)