RFR: 8327137: Add test for ConcurrentModificationException in BasicDirectoryModel

[Alexey Ivanov]

On Thu, 14 Mar 2024 19:37:48 GMT, Sergey Bylokhov <serb at openjdk.org> wrote:

>> I'm adding a regression test for [JDK-8323670](https://bugs.openjdk.org/browse/JDK-8323670) and [JDK-8307091](https://bugs.openjdk.org/browse/JDK-8307091); it's also a regression test for [JDK-8240690](https://bugs.openjdk.org/browse/JDK-8240690).
>> 
>> I referenced this test in PR #17462 in [this comment](https://github.com/openjdk/jdk/pull/17462#issuecomment-1914844026). I fine-tuned the test since that time.
>> 
>> The test doesn't fail all the time without the fix for JDK-8323670, however, it fails sometimes. If you run the test several times, it will likely fail _without the fix_.
>> 
>> For me, the test fails about 10 times from 40 runs in the CI. It fails on macOS more frequently than on Linux.
>> 
>> When the test passes, it usually completes in 5 minutes.
>> 
>> **How the test works**
>> 
>> The test creates a temporary directory in the current directory and creates a number of files in it. (The number of files is controlled by `NUMBER_OF_THREADS` constant). Then the test creates `JFileChooser` in the temporary directory.
>> 
>> The test starts several _scanner_ threads, the number is controlled by `NUMBER_OF_THREADS`, which repeatedly call `fileChooser.rescanCurrentDirectory()`. This results in calling `BasicDirectoryModel.validateFileCache` which starts a background thread — "Basic L&F File Loading Thread" — to enumerate the files.
>> 
>> A timer is used to create new files in the directory that the file chooser is using.
>> 
>> After enumerating the files, the File Loading Thread posts an event to EDT. The event updates `fileCache` and fires a `ListDataEvent`.
>> 
>> If the File Loading Thread is iterating over `fileCache` using `Iterator` (when `fileCache.subList` or `fileCache.equals` is running; or a new `Vector` instance is created from a `fileCache` or its sublist) and `fileCache` is being updated on EDT, then `ConcurrentModificationException` is thrown.
>> 
>> On Linux and on _headless_ macOS, `ShellFolder.invoke` is executed in the caller, which makes it easier to reproduce the issue. Because of [JDK-8325179](https://bugs.openjdk.org/browse/JDK-8325179), there are several File Loading Threads, which also helps to reproduce the issue.
>> 
>> On _headful_ macOS, the `BasicDirectoryModel` is not used, so the test does not reproduce the issue.
>> 
>> On Windows, the test does not fail or fails with `OutOfMemoryError`. It is because all the File Loading Threads are serialised on the COM thread, `ShellFolder.invoke` submits the task to the COM thread and waits for i...
>
> test/jdk/javax/swing/plaf/basic/BasicDirectoryModel/ConcurrentModification.java line 1:
> 
>> 1: import java.io.IOException;
> 
> the header is missing.

Do you mean the license? Yes, it needs the copyright and license block.

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PR Review Comment: https://git.openjdk.org/jdk/pull/18109#discussion_r1526098180