[Webkit-unassigned] [Bug 159537] New: REGRESSION(184445): Need to insert a StoreBarrier when we don't know child's epoch
bugzilla-daemon at webkit.org
bugzilla-daemon at webkit.org
Thu Jul 7 16:49:31 PDT 2016
https://bugs.webkit.org/show_bug.cgi?id=159537
Bug ID: 159537
Summary: REGRESSION(184445): Need to insert a StoreBarrier when
we don't know child's epoch
Classification: Unclassified
Product: WebKit
Version: WebKit Nightly Build
Hardware: Unspecified
OS: Unspecified
Status: NEW
Severity: Major
Priority: P2
Component: JavaScriptCore
Assignee: webkit-unassigned at lists.webkit.org
Reporter: msaboff at apple.com
In StoreBarrierInsertionPhase::considerBarrier(Edge base, Edge child), there is the following comment and code:
// Something we watch out for here is that the null epoch is a catch-all for objects
// allocated before we did any epoch tracking. Two objects being in the null epoch
// means that we don't know their epoch relationship.
if (!!base->epoch() && base->epoch() >= child->epoch()) {
if (verbose)
dataLog(" Rejecting because of epoch ordering.\n");
return;
}
The test doesn't check that the child's epoch is null and therefore we won't insert a barrier for the case where we allocate the base object, but don't know when the child object was allocated.
<rdar://problem/23438751>
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