RFR: 8359437: Make users and test suite not able to set LockingMode flag

[David Holmes]

On Tue, 17 Jun 2025 08:39:49 GMT, Anton Artemov <duke at openjdk.org> wrote:

> This PR contains changes for the 1st phase of the `LockingMode` flag obsoletion. 
> 
> The work is done by @fbredber, I have taken it over and am finishing it while he's on vacation. 
> 
> In the 1st phase one keeps the `LockingMode` variable in all places, but makes it non-settable from the command line. All the C1 and C2 code related to legacy locking will still be in place (but as dead code) and removed later (phase 2).
> 
> Lightweight locking is the default locking from now on.
> 
> Tested in tiers 1 - 7.

Changes are looking okay to me, but we have an issue with bug management that needs to be resolved - and probably need a new bug and PR.

test/jtreg-ext/requires/VMProps.java line 424:

> 422:      * Note: Lightweight locking does not support RTM (for now).
> 423:      */
> 424:     protected String vmRTMCompiler() {

[JDK-8358542](https://bugs.openjdk.org/browse/JDK-8358542) exists to remove this so you would need to add that bug id to this PR. However, it seems the bug management for this has gotten completely messed up so you may need to scrap this PR and file a new bug and PR for this part.

-------------

PR Review: https://git.openjdk.org/jdk/pull/25847#pullrequestreview-2952042310
PR Review Comment: https://git.openjdk.org/jdk/pull/25847#discussion_r2162873188