Replace the entire observers list when adding/removing observers in o… #796
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Added a test that deliberately accesses on two threads. This crashes the old implementation. |
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…rder to completely avoid concurrency issues (adding/removing an observer while observer notifications are happening).
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Goal
Fixes https://bugsnag.atlassian.net/browse/PLAT-5007
Design
Instead of adding/removing observers from the observer list directly, make a copy of the list, modify the copy, then replace the original. This makes concurrency issues (where an observer gets added/removed while the observer list is being walked) impossible.
So long as the list remains small (100 or so entries), the CPU cost is negligible. We don't expect to ever see more than around 10 observers here no matter what future features we add.