RFR: 8323670: A few client tests intermittently throw ConcurrentModificationException

[Alexey Ivanov]

On Fri, 26 Jan 2024 22:57:49 GMT, Sergey Bylokhov <serb at openjdk.org> wrote:

> > I don't think we are able to trace it out, since the issue intermittent and previously I had made a copy of the vector list before checking for equality of the list. There was again an issue in the code which I used to copy to a temporary vector. So now instead of using` AbstractList.equals` I'm using iterators and comparing every element within synchronized method.
> 
> I think we should start investigating this one, probably by adding special delays/asserts into the JDK to track down on what threads the data is modified and used.

According to my analysis above, there there are two threads. (The third thread is also possible if `validateFileCache` is called not on EDT.) The only thread that modifies `fileCache` is EDT with `DoChangeContents`. Then the `ShellFolder` thread reads from `fileCache` *without synchronisation*, which allows the contents of `fileCache` to be modified concurrently.

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PR Comment: https://git.openjdk.org/jdk/pull/17462#issuecomment-1912818487