744489 - Fix incremental GC assertion in ValidateIncrementalMarking

Status: RESOLVED FIXED

(Core :: JavaScript Engine, defect)

Description

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

Attachment: patch

I was a little overzealous in bug 739899 when I tried to remove all full GC flags. As a consequence, the following can now happen:

1. Start an incremental GC with all compartments being collected. Therefore, the atoms compartment can be collected.
2. A new compartment is created
3. When the GC is finished, call ValidateIncrementalMarking.
4. It calls MarkRuntime again. This time, since the new compartment is not being collected, we mark all atoms.
5. ValidateIncrementalMarking asserts because the incremental GC didn't mark all the atoms, while the non-incremental one did.

This is a bogus assertion. We're not required to mark all atoms in this situation. Any atoms pointed to by the new compartment either existed before or else they were new, and we'll mark them either way.

The patch just adds a "full GC" flag that is set at the beginning of the incremental GC and used by both calls to MarkRuntime.

Comment 1

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

https://hg.mozilla.org/integration/mozilla-inbound/rev/ae32cca25ce0

Comment 2

[Marco Bonardo [:mak]]

https://hg.mozilla.org/mozilla-central/rev/ae32cca25ce0