RFR: 8325179: Race in BasicDirectoryModel.validateFileCache [v3]

[Sergey Bylokhov]

On Wed, 6 Mar 2024 11:27:08 GMT, Alexey Ivanov <aivanov at openjdk.org> wrote:

>> Ensure access to the `filesLoader` field of `BasicDirectoryModel` is synchronized.
>> 
>> Without synchronization, a thread checks if `filesLoader` is not null and creates a new `FilesLoader` thread. If the thread is pre-empted between these two operations, another thread or even several threads can see the `null` value and create new `FilesLoader` threads.
>> 
>> The same way, `BasicDirectoryModel.invalidateFileCache` needs to be synchornized to interrupt the current `filesLoader` and assign `null`.
>> 
>> This bug allows reproducing `ConcurrentModificationException` seen in [JDK-8323670](https://bugs.openjdk.org/browse/JDK-8323670) and [JDK-8307091](https://bugs.openjdk.org/browse/JDK-8307091) using the test in PR #18109.
>
> Alexey Ivanov has updated the pull request incrementally with one additional commit since the last revision:
> 
>   Store the size of fileCache inside synchronized block

src/java.desktop/share/classes/javax/swing/plaf/basic/BasicDirectoryModel.java line 534:

> 532:         @Override
> 533:         public void run() {
> 534:             if (fetchID.get() != fid) {

How it will work if the "FilesLoader" was created already but before loading the files the "invalidateFileCache" was called, before the patch we stop execution due to "doFire=false".

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PR Review Comment: https://git.openjdk.org/jdk/pull/18111#discussion_r1525420964