186284 2018-06-04 14:17:01 -0700 Set the activeLength of all ScratchBuffers to zero when exiting the VM 2018-06-04 22:15:02 -0700 1 1 1 Unclassified WebKit JavaScriptCore WebKit Nightly Build Unspecified Unspecified RESOLVED FIXED InRadar P2 Normal --- 1 simon.fraser saam commit-queue ews-watchlist ggaren keith_miller mark.lam msaboff saam simon.fraser webkit-bug-importer ysuzuki oldest_to_newest 1429898 0 simon.fraser 2018-06-04 14:17:01 -0700 Even after the fix for bug 186223, there are code paths that can leave ScratchBuffers with non-zero activeLength(), which can potentially cause things to be GC roots via the conservative scan. We should just set the activeLength of all scratch buffers to zero when leaving VM entry scope. 1429899 1 webkit-bug-importer 2018-06-04 14:17:47 -0700 <rdar://problem/40780738> 1429905 2 saam 2018-06-04 14:34:44 -0700 Patch forthcoming 1429919 3 341922 saam 2018-06-04 15:05:14 -0700 Created attachment 341922 patch 1429967 4 341922 keith_miller 2018-06-04 16:50:01 -0700 Comment on attachment 341922 patch r=me. 1429970 5 saam 2018-06-04 17:00:23 -0700 Keith mentioned doing this in a follow-up: https://bugs.webkit.org/show_bug.cgi?id=186292 1429971 6 341940 saam 2018-06-04 17:03:31 -0700 Created attachment 341940 patch for landing 1429980 7 341940 commit-queue 2018-06-04 18:13:04 -0700 Comment on attachment 341940 patch for landing Clearing flags on attachment: 341940 Committed r232490: <https://trac.webkit.org/changeset/232490> 1429981 8 commit-queue 2018-06-04 18:13:06 -0700 All reviewed patches have been landed. Closing bug. 1429999 9 ggaren 2018-06-04 19:28:08 -0700 Under what conditions do we enter the garbage collector with a live scratch buffer? OSR exit with object re-materialization, maybe? Just wondering why we need to mark scratch buffers at all... 1430026 10 saam 2018-06-04 22:15:02 -0700 (In reply to Geoffrey Garen from comment #9) > Under what conditions do we enter the garbage collector with a live scratch > buffer? OSR exit with object re-materialization, maybe? Just wondering why > we need to mark scratch buffers at all... There are probably more cases than that. Some quick grepping: - OSR entry in loops and catch. I guess it's non-obvious if we need contents marked here. - Array push with > 1 argument - NewArray - NewArrayWithSpread - OSR exit as you said 341922 2018-06-04 15:05:14 -0700 2018-06-04 17:03:31 -0700 patch a-backup.diff text/plain 3199 saam SW5kZXg6IFNvdXJjZS9KYXZhU2NyaXB0Q29yZS9DaGFuZ2VMb2cKPT09PT09PT09PT09PT09PT09 PT09PT09PT09PT09PT09PT09PT09PT09PT09PT09PT09PT09PT09PT09PT09PT09PQotLS0gU291 cmNlL0phdmFTY3JpcHRDb3JlL0NoYW5nZUxvZwkocmV2aXNpb24gMjMyNDgwKQorKysgU291cmNl L0phdmFTY3JpcHRDb3JlL0NoYW5nZUxvZwkod29ya2luZyBjb3B5KQpAQCAtMSwzICsxLDI5IEBA CisyMDE4LTA2LTA0ICBTYWFtIEJhcmF0aSAgPHNiYXJhdGlAYXBwbGUuY29tPgorCisgICAgICAg IFNldCB0aGUgYWN0aXZlTGVuZ3RoIG9mIGFsbCBTY3JhdGNoQnVmZmVycyB0byB6ZXJvIHdoZW4g ZXhpdGluZyB0aGUgVk0KKyAgICAgICAgaHR0cHM6Ly9idWdzLndlYmtpdC5vcmcvc2hvd19idWcu Y2dpP2lkPTE4NjI4NAorICAgICAgICA8cmRhcjovL3Byb2JsZW0vNDA3ODA3Mzg+CisKKyAgICAg ICAgUmV2aWV3ZWQgYnkgTk9CT0RZIChPT1BTISkuCisKKyAgICAgICAgU2ltb24gcmVjZW50bHkg 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