1244921 - Script blocker in MessageChannel causes code to run at unexpected times

Status: RESOLVED DUPLICATE of bug 1191145

(Core :: IPC, defect)

Description

[Bill McCloskey [inactive unless it's an emergency] (:billm)]

Daniel found this issue when running NoScript. The bug is here:
https://dxr.mozilla.org/mozilla-central/source/ipc/glue/MessageChannel.cpp#1407

Here is the sequence of events:
- CPOW comes in from the parent.
- It gets dispatched and it causes a script to be enqueued with the script blocker at the line I referenced.
- In the script blocker destructor, we run that script.
- The script sends a normal priority sync message.
- This message is considered to be in the same transaction as the CPOW because AutoEnterTransaction is still on the stack from DispatchMessage.
- However, it doesn't cause the CPOW to be cancelled because mDispatchingSyncMessagePriority is 0, since the script runs outside of the AutoSetValue for that field.

Comment 1

[Bill McCloskey [inactive unless it's an emergency] (:billm)]

This should be fixed by bug 1244921, assuming it sticks this time.

Comment 2

[Bill McCloskey [inactive unless it's an emergency] (:billm)]

Meant bug 1191145.

Comment 3

[Daniel Holbert [:dholbert]]

Looks like you're right. I can't reproduce the hang (bug 1239767) anymore (in a debug inbound build at least), so I've duped that bug to bug 1191145.

Should we dupe this bug as well? Or resolve it as FIXED/WFM with a dependency on bug 1191145?