RFR: 8332084: Ensure JdkConsoleImpl.restoreEcho visibility in a shutdown hook [v8]

[Naoto Sato]

On Tue, 21 May 2024 22:51:14 GMT, Naoto Sato <naoto at openjdk.org> wrote:

>> Making sure `restoreEcho` correctly reflects the state in the shutdown thread, which differs from the application's thread that issues the `readPassword()` method.
>
> Naoto Sato has updated the pull request incrementally with one additional commit since the last revision:
> 
>   Used a dedicate lock for restoreEcho

Based on an internal discussion regarding Stuart's above comment, I changed the `restoreEcho` field back to the original. Instead of making it volatile, synchronizing it with a dedicated lock would ensure visibility and atomic status updates (no races).

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PR Comment: https://git.openjdk.org/jdk/pull/19184#issuecomment-2123561717