The scheduler currently has different queues for starting jobs and cancellation jobs to sync with main thread and worker thread. It should be handle sequential for registering the starting job and canceling the job.
Created attachment 325592 [details]
Comment on attachment 325592 [details]
Clearing flags on attachment: 325592
Committed r224322: <https://trac.webkit.org/changeset/224322>
All reviewed patches have been landed. Closing bug.