1652719 - Stop allowing JS helper thread access to CHECK_THREAD APIs

Status: RESOLVED FIXED

(Core :: JavaScript Engine, task, P3)

Description

[Ted Campbell [:tcampbell]]

For JSAPI entry points, we often AssertHeapIsIdle() and CHECK_THREAD(). This is a bit of a footgun on helper-threads (eg off-thread parse) since the heap my intermittently be not idle, but CHECK_THREAD has a blanket allow for helper-threads.

To prevent intermittent issues from being introduced, we should disallow helper-threads for APIs that CHECK_THREAD. Currently the only violation is Atomize/AtomizeChars which I propose just removing the CHECK_THREAD from for now.

Comment 1

[Ted Campbell [:tcampbell]]

Attachment: Bug 1652719 - Stop allowing JS helper thread access to CHECK_THREAD APIs

SpiderMonkey APIs often use CHECK_THREAD and AssertHeapIsIdle, but this can
be a footgun when they are called from helper-threads since often nothing
ensures the heap is idle. Instead, this patch updates the CHECK_THREAD assert
to disallow helper-thread access to prevent misuses. The checks in Atomize
and AtomizeChars are removed since those are (currently) allowed on helper
threads.

Comment 2

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/integration/autoland/rev/f4c6aeca6e2f
Stop allowing JS helper thread access to CHECK_THREAD APIs r=jandem

Comment 3

[Andreea Pavel [:apavel]]

https://hg.mozilla.org/mozilla-central/rev/f4c6aeca6e2f