1301519 - GetCurrentThreadWorkerPrivate() crashes if called due to nsCycleCollector_shutdown()

Status: RESOLVED FIXED

(Core :: DOM: Workers, defect)

Description

[Ben Kelly [:bkelly, not reviewing]]

While working on bug 1300658 I have run into a crash in GetCurrentThreadWorkerPrivate().  Basically we are getting a nullptr context private here:

  https://dxr.mozilla.org/mozilla-central/source/dom/workers/RuntimeService.cpp#1459

This is happening because the GetCurrentThreadWorkerPrivate() is being called in clean up code triggered by the nsCycleCollector_shutdown() here:

  https://dxr.mozilla.org/mozilla-central/source/dom/workers/RuntimeService.cpp#1071

The cycle collector shutdown occurs after clearing the context private.

Comment 1

[Ben Kelly [:bkelly, not reviewing]]

Attachment: Don't crash if GetCurrentThreadWorkerPrivate() is called during worker shutdown. r=baku

Currently there is a window during ~WorkerJSRuntime() where the context private has been cleared, but the CycleCollectedRuntime::Get() method will still return non-nullptr.

This is a problem if anything tries to call GetCurrentThreadWorkerPrivate() during this window.  Unfortunately, ~WorkerJSRuntime() also calls nsCycleCollector_shutdown() at this point.  This can execute arbitrary code through the destructors of cycle collected objects.

This patch makes us handle the nullptr context private a bit better.

https://treeherder.mozilla.org/#/jobs?repo=try&revision=a95c0fdabb09

Comment 2

[Ben Kelly [:bkelly, not reviewing]]

Attachment: Don't crash if GetCurrentThreadWorkerPrivate() is called during worker shutdown. r=baku

Removed unrelated code from patch.  Please see previous comments for explanation.

Comment 3

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/integration/mozilla-inbound/rev/00f3449636ba
Don't crash if GetCurrentThreadWorkerPrivate() is called during worker shutdown. r=baku

Comment 4

[Wes Kocher (:KWierso) (Not reading bugmail; email directly if needed)]

https://hg.mozilla.org/mozilla-central/rev/00f3449636ba