REOPENED303958
Layout milestone notifications should be dispatched asynchronously 
https://bugs.webkit.org/show_bug.cgi?id=303958
Summary Layout milestone notifications should be dispatched asynchronously
jlee53
Reported 2025-12-10 17:09:57 PST
Javascript execution should not happen during in the process of updating the layout. When a layout milestone notification fires, the layout may not be completed but client callbacks to layout milestone notifications can trigger Javascript execution. This results in javascript execution failing (and consequently crashing) to run in the middle of the layout process because it is correctly not permitted to do so. We delay firing layout milestone notifications by dispatching them asychronously in order to prevent this.
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Add attachment proposed patch, testcase, etc.
jlee53
Comment 1 2025-12-10 17:10:24 PST
<rdar://problem/153254633>
jlee53
Comment 2 2025-12-10 17:11:50 PST
Pull request: https://github.com/WebKit/WebKit/pull/55213
jlee53
Comment 3 2025-12-16 13:46:31 PST
Pull request: https://github.com/WebKit/WebKit/pull/55502
EWS
Comment 4 2025-12-16 19:58:34 PST
Committed 304572@main (bf24e9a12c17): <https://commits.webkit.org/304572@main> Reviewed commits have been landed. Closing PR #55213 and removing active labels.
Chris Dumez
Comment 5 2025-12-18 19:28:49 PST
Reopened Bugzilla. 304572@main caused a 17% PLT regression, tracking revert in https://bugs.webkit.org/show_bug.cgi?id=304460.
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