Jigsaw Enhancement RFR round #2: 8159145 Add JVMTI function GetModuleByPackageName

[Jiangli Zhou]

Hi Serguei,

The comment in the following assert is outdated. There is no get_module_from_pkg. Should it be changed to get_module_by_package_name()?

 804   assert(ModuleEntryTable::javabase_defined(),
 805          "Attempt to call get_module_from_pkg before java.base is defined");

It’s not part of your change, I just happen to notice it. In the same get_module_by_package_name(), both the ‘if’ and ‘else’ cases have return statement. The ‘return NULL’ at line 825 seems will never reached and not needed. 

Thanks,
Jiangli

> On Jun 22, 2016, at 4:07 AM, serguei.spitsyn at oracle.com wrote:
> 
> Here are new hotspot webrev where I've fixed the comments from Alan and Christian.
> 
> Hotspot:
> http://cr.openjdk.java.net/~sspitsyn/webrevs/2016/hotspot/8159145-jigsaw-jvmti-pkg.2
> 
> 
> The Jdk webrev is the same:
> http://javaweb.sfbay.sun.com/java/svc/ss45998/webrevs/2016/hotspot/8159145-jigsaw-jvmti-pkg.jdk1/
> 
> 
> Thanks,
> Serguei
> 
> 
> On 6/21/16 02:54, serguei.spitsyn at oracle.com wrote:
>> 
>> Please, review the Jigsaw fix for the enhancement:
>> https://bugs.openjdk.java.net/browse/JDK-8159145
>> 
>> 
>> The Hotspot webrev:
>> http://javaweb.sfbay.sun.com/java/svc/ss45998/webrevs/2016/hotspot/8159145-jigsaw-jvmti-pkg.1/
>> 
>> The Jdk webrev:
>> http://javaweb.sfbay.sun.com/java/svc/ss45998/webrevs/2016/hotspot/8159145-jigsaw-jvmti-pkg.jdk1/
>> 
>> 
>> Summary:
>> 
>> JVM TI agents that instrument code in named modules need the Module at class load time.
>> 
>>  One way to do this is by introducing a new ClassFileLoadHook that takes an additional parameter but this approach is disruptive.
>>  The alternative option is a JVM TI function that maps a classloader + package name to a module.
>>  We were initially not confident with this approach so we introduced it as JVM function JVM_GetModuleByPackageName.
>>  Based on experience to date then this approach seems okay and so this function needs to be promoted to a JVMTI function.
>> 
>>  This fix is to introduce new JVMTI function GetModuleByPackageName.
>>  It includes new jtreg test with native JVMTI agent.
>> 
>>  A CCC is fast-tracked and getting an approval is in progress.
>> 
>> Testing:
>>   Run newly developed jtreg test.
>> 
>> Thanks,
>> Serguei
> 

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