RFR: 8365190: Remove LockingMode related code from share

[Roberto Castañeda Lozano]

On Tue, 2 Sep 2025 08:24:10 GMT, Fredrik Bredberg <fbredberg at openjdk.org> wrote:

> Since the integration of [JDK-8359437](https://bugs.openjdk.org/browse/JDK-8359437) the `LockingMode` flag can no longer be set by the user. After that, a number of PRs has been integrated which has removed all `LockingMode` related code from all platforms (except from zero, which is done in this PR).
> 
> This PR removes `LockingMode` related code from the shared (non-platform specific) files. It also removes the `LockingMode` variable itself.
> 
> Passes tier1-tier5 with no added problems.

src/hotspot/share/opto/phaseX.cpp line 1672:

> 1670:     // Found (linux x64 only?) with:
> 1671:     //   serviceability/sa/ClhsdbThreadContext.java
> 1672:     //   -XX:+UnlockExperimentalVMOptions -XX:LockingMode=1 -XX:+IgnoreUnrecognizedVMOptions -XX:VerifyIterativeGVN=1110

For traceability, I suggest leaving this line untouched and adding a comment in the next line clarifying that `-XX:LockingMode` is not available anymore.

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PR Review Comment: https://git.openjdk.org/jdk/pull/27041#discussion_r2316150051