RFR: 8336299: Improve GCLocker stall diagnostics [v6]

[Aleksey Shipilev]

On Mon, 12 Aug 2024 22:39:25 GMT, Neethu Prasad <nprasad at openjdk.org> wrote:

>> **Notes**
>> Adding logs to get more visibility into how fast a thread resumes from allocation stall. 
>> 
>> **Testing**
>> * tier 1, tier 2, hotspot_gc tests.
>> 
>> Example log messages
>> 
>> 1. Last thread exiting. Performing GC after exiting critical section. Thread "main" 0 locked.
>> 
>> 2. Thread exiting critical region. Thread "main" 0 locked.
>> 
>> 3. Thread stalled by JNI critical section. Resumed after 1294ms. Thread "Thread-0".
>> 
>> 4. Thread blocked to enter critical region. Resumed after 1280ms. Thread "SIGINT handler".
>
> Neethu Prasad has updated the pull request incrementally with one additional commit since the last revision:
> 
>   address feedback regarding logger potentially getting instantiated multiple times

Looks good to me, thanks.

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Marked as reviewed by shade (Reviewer).

PR Review: https://git.openjdk.org/jdk/pull/20277#pullrequestreview-2251003645