RFR: 8338383: Implement JEP 491: Synchronize Virtual Threads without Pinning [v5]

[Patricio Chilano Mateo]

On Wed, 23 Oct 2024 05:43:53 GMT, David Holmes <dholmes at openjdk.org> wrote:

>> Patricio Chilano Mateo has updated the pull request incrementally with one additional commit since the last revision:
>> 
>>   Address David's comments to ObjectMonitor.hpp
>
> src/hotspot/share/runtime/objectMonitor.hpp line 302:
> 
>> 300:   void      set_owner_from(int64_t old_value, JavaThread* current);
>> 301:   // Set _owner field to tid of current thread; current value must be ANONYMOUS_OWNER.
>> 302:   void      set_owner_from_BasicLock(JavaThread* current);
> 
> Shouldn't tid there be the basicLock?

So the value stored in _owner has to be ANONYMOUS_OWNER. We cannot store the BasicLock* in there as before since it can clash with some other thread's tid. We store it in the new field _stack_locker instead.

> src/hotspot/share/runtime/objectMonitor.hpp line 334:
> 
>> 332: 
>> 333:   // Returns true if BasicLock* stored in _stack_locker
>> 334:   // points to current's stack, false othwerwise.
> 
> Suggestion:
> 
>   // points to current's stack, false otherwise.

Fixed.

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PR Review Comment: https://git.openjdk.org/jdk/pull/21565#discussion_r1814187730
PR Review Comment: https://git.openjdk.org/jdk/pull/21565#discussion_r1814187856