RFR: 8359437: Make users and test suite not able to set LockingMode flag [v4]

[Alan Bateman]

On Tue, 24 Jun 2025 11:16:21 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.
>
> Anton Artemov has updated the pull request incrementally with one additional commit since the last revision:
> 
>   8359437: Addressed reviewer's comments

test/hotspot/jtreg/serviceability/jvmti/vthread/StopThreadTest/StopThreadTest.java line 280:

> 278: 
> 279:     static boolean preemptableVirtualThread() {
> 280:         return is_virtual && !isBoundVThread;

I think this is the last usage of ManagementFactory and HotSpotDiagnosticMXBean in this test so the imports can be expunged.

test/jdk/jdk/internal/vm/Continuation/Basic.java line 426:

> 424:         return ManagementFactory.getPlatformMXBean(HotSpotDiagnosticMXBean.class)
> 425:                     .getVMOption("LockingMode").getValue().equals("1");
> 426:     }

Likely the same here.

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PR Review Comment: https://git.openjdk.org/jdk/pull/25847#discussion_r2163891432
PR Review Comment: https://git.openjdk.org/jdk/pull/25847#discussion_r2163896486