1638506 - Potential dispatching in ProfilerParent may happen after thread shutdown

Status: RESOLVED FIXED

(Core :: Gecko Profiler, defect, P2)

Description

[Gerald Squelart (he/him) (not at Mozilla since 2022-09-15)]

Spawned from bug 1637890 and https://phabricator.services.mozilla.com/D75497#2298876

ProfilerParentTracker is destroyed during the ShutdownFinal phase, during which it closes extant channels, which may cause pending promises to be rejected, and that triggers a dispatch to handle the rejection.

We should prevent this late dispatch. Some possible solutions:
A. Destroy ProfilerParentTracker earlier (Shutdown or ShutdownThreads phase). I'm not entirely sure if it's safe to manually close channels.
B. Reject promises earlier, but we'd have to handle potential late messages -- is that even possible?
C. Disconnect promise handlers, but that's more code to keep track of them, and I'm not sure it would prevent dispatching?

The fix for bug 1637890 should solve the crash, but it would still be nice to do the right thing!

Comment 1

[Jean-Yves Avenard [:jya]]

(In reply to Gerald Squelart [:gerald] (he/him) from comment #0)

C. Disconnect promise handlers, but that's more code to keep track of them, and I'm not sure it would prevent dispatching?

If you use a MozPromiseRequestHolder to hold the promise returned by IPDL; disconnecting will prevent any tasks from being dispatched.

Comment 2

[Gerald Squelart (he/him) (not at Mozilla since 2022-09-15)]

Attachment: Bug 1638506 - Destroy ProfilerParentTracker before threads are shut down - r?jya,canaltinova

When the tracker is destroyed, any extant channel is closed, this can trigger the rejection of pending promises, which dispatch tasks to promise handlers. So we need to ensure that this happens before threads cannot service dispatches anymore.

Comment 3

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/integration/autoland/rev/ca6bc38ba7f7
Destroy ProfilerParentTracker before threads are shut down - r=jya,canaltinova

Comment 4

[Cristian Brindusan [:cbrindusan]]

https://hg.mozilla.org/mozilla-central/rev/ca6bc38ba7f7