RFR: 8323670: A few client tests intermittently throw ConcurrentModificationException

[Alexey Ivanov]

On Wed, 17 Jan 2024 12:55:52 GMT, Tejesh R <tr at openjdk.org> wrote:

> Suggested fix [JDK-8307091](https://bugs.openjdk.org/browse/JDK-8307091) also created concurrent exception intermittently (monthly once/quarterly once) on CI system. The issue was not able to be reproduced yet, hence proposing an alternative fix which uses iterators to compare the List.
> CI testing shows green.

Taking the above into account, I appears that the code inside `ShellFolder.invoke.call` should actually be inside `synchronized (fileCache)`. It would resolve `ConcurrentModificationException`.

And you should revert the changes you made in [JDK-8323670](https://bugs.openjdk.org/browse/JDK-8323670). This bug is the proof that fix didn't help.

Ideally, we should have a test which reproduces the problem… Yet, as with all concurrency issues, writing such a test could be very hard.

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PR Comment: https://git.openjdk.org/jdk/pull/17462#issuecomment-1909916062