RFR: 8212879: Make JVMTI TagMap table concurrent [v2]

[Coleen Phillimore]

On Mon, 2 Nov 2020 15:18:43 GMT, Erik Österlund <eosterlund at openjdk.org> wrote:

>> Coleen Phillimore has updated the pull request incrementally with one additional commit since the last revision:
>> 
>>   Code review comments from StefanK.
>
> test/hotspot/jtreg/vmTestbase/nsk/jvmti/scenarios/capability/CM02/cm02t001/cm02t001.cpp line 656:
> 
>> 654:         result = NSK_FALSE;
>> 655: 
>> 656:     printf("Object free events %d\n", ObjectFreeEventsCount);
> 
> Is this old debug info you forgot to remove? Other code seems to use NSK_DISPLAY macros instead.

yes, removed it.

> src/hotspot/share/prims/jvmtiTagMap.cpp line 345:
> 
>> 343: 
>> 344:   // Check if we have to process for concurrent GCs.
>> 345:   check_hashmap(false);
> 
> Maybe add a comment stating the parameter name, as was done in other callsites for check_hashmap.

Ok, will I run afoul of the ZGC people putting the parameter name after the parameter and the rest of the code, it is before?

> src/hotspot/share/prims/jvmtiTagMap.cpp line 3009:
> 
>> 3007:           // Lock each hashmap from concurrent posting and cleaning
>> 3008:           MutexLocker ml(tag_map->lock(), Mutex::_no_safepoint_check_flag);
>> 3009:           tag_map->hashmap()->unlink_and_post(tag_map->env());
> 
> This could call unlink_and_post_locked instead of manually locking.

Ok, 2 requests.  I can call that then and move the logging.

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PR: https://git.openjdk.java.net/jdk/pull/967