[Webkit-unassigned] [Bug 167208] New: The mutator needs to fire a barrier after memmoving stuff around in an object that the GC scans
bugzilla-daemon at webkit.org
bugzilla-daemon at webkit.org
Thu Jan 19 12:06:34 PST 2017
https://bugs.webkit.org/show_bug.cgi?id=167208
Bug ID: 167208
Summary: The mutator needs to fire a barrier after memmoving
stuff around in an object that the GC scans
Classification: Unclassified
Product: WebKit
Version: WebKit Nightly Build
Hardware: All
OS: All
Status: NEW
Severity: Normal
Priority: P2
Component: JavaScriptCore
Assignee: webkit-unassigned at lists.webkit.org
Reporter: fpizlo at apple.com
We didn't used to need these kinds of barriers, but now we do!
It used to be that if you moved a value from one place to another in the same object then there is no need for a barrier because the generational GC would have no need to know that the referent still continues to refer to the same referee.
But the concurrent GC might scan that object as the mutator moves pointers around in it. If the ordering is right, this could mean that the collector never sees some of those pointers. This can be fixed by adding a barrier.
This bug covers the most obvious cases I found. There may be more and I'll continue to audit.
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