[lworld] RFR: 8255396: [lworld] locking breaks oopDesc is_flatArray/is_nullfreeArray type checks

[Sergey Kuksenko]

On 10/26/20 9:53 AM, Sergey Kuksenko wrote:
> I have a question about the following methods from markWord.hpp:
>
> bool is_locked()const {
>   return (mask_bits(value(),lock_mask_in_place) !=unlocked_value);
> }
> bool is_unlocked()const {
>   return (mask_bits(value(),biased_lock_mask_in_place) ==unlocked_value);
> }
>
> First of all these methods are not symmetrical. 
> "lock_mask_in_place"==0x011 when "biased_lock_mask_in_place"==0x111.

Sorry, misprint. I mean 0b011 & 0b111


>
> The second. If we invoke is_unlocked() on inline/primitive object we 
> get "false". is_locked() on inline also gives "false".
> I am not sure if may cause an error, maybe all such checks are 
> preguarded with is_inline_type().
>
> The third. Valhalla can't work with BiasedLocking. I think it would be 
> better to remove all usage of BiasedLocking constant in Valhalla to 
> avoid errors. As far as I understand, BiasedLocking has became 
> "obsolete" in jdk16.
> That means:
> // When the JDK version reaches 'obsolete_in' limit, the JVM will 
> continue accepting this flag on // the command-line, while issuing a 
> warning and ignoring the flag value.
>
> So, now BasedLocking can't be turn on in mainline jdk. To simplify 
> merging, maybe make sense to remove biased locking constants and masks 
> in mainline jdk.
>
>
> On 10/26/20 7:23 AM, David Simms wrote:
>> Added unlocked test and fallback to klass
>>
>> -------------
>>
>> Commit messages:
>>   - 8255396: [lworld] locking breaks oopDesc 
>> is_flatArray/is_nullfreeArray type checks
>>
>> Changes: https://git.openjdk.java.net/valhalla/pull/238/files
>>   Webrev: 
>> https://webrevs.openjdk.java.net/?repo=valhalla&pr=238&range=00
>>    Issue: https://bugs.openjdk.java.net/browse/JDK-8255396
>>    Stats: 36 lines in 2 files changed: 33 ins; 1 del; 2 mod
>>    Patch: https://git.openjdk.java.net/valhalla/pull/238.diff
>>    Fetch: git fetch https://git.openjdk.java.net/valhalla 
>> pull/238/head:pull/238
>>
>> PR: https://git.openjdk.java.net/valhalla/pull/238