Jigsaw Enhancement RFR round #3: 8159145 Add JVMTI function GetNamedModule

[harold seigel]

Hi Serguei,

It looks good!

Thanks, Harold


On 6/28/2016 12:37 PM, serguei.spitsyn at oracle.com wrote:
> Hi Harold,
>
> Thank you again for the comments!
> This is the updated webrev:
> http://cr.openjdk.java.net/~sspitsyn/webrevs/2016/hotspot/8159145-jigsaw-jvmti-pkg.5/
>
> Thanks,
> Serguei
>
>
> On 6/28/16 07:32, harold seigel wrote:
>>
>> Hi Serguei,
>>
>> Looks good.
>>
>> 1. In modules.cpp, the first assert in get_named_module() has the 
>> wrong function name:
>>
>> 825 assert(ModuleEntryTable::javabase_defined(),
>> 826 "Attempt to call *get_module_by_package_name* before java.base is 
>> defined");
>>
>> 2. Also, is a check needed to ensure that package_str is not null?
>>
>> 3. Is the ResourceMark(THREAD) needed at line 824?
>>
>> Thanks, Harold
>>
>> On 6/28/2016 4:54 AM, serguei.spitsyn at oracle.com wrote:
>>> Hi David,
>>>
>>> Thank you for the comments!
>>> I agree with you.
>>>
>>> Updated Hotspot webrev:
>>> http://cr.openjdk.java.net/~sspitsyn/webrevs/2016/hotspot/8159145-jigsaw-jvmti-pkg.4/ 
>>>
>>>
>>>
>>> Thanks,
>>> Serguei
>>>
>>>
>>>
>>> On 6/27/16 22:06, David Holmes wrote:
>>>> Hi Serguei,
>>>>
>>>> Overall this looks a lot clearer/simpler.
>>>>
>>>> On 28/06/2016 2:20 PM, serguei.spitsyn at oracle.com wrote:
>>>>> On 6/27/16 21:08, 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://cr.openjdk.java.net/~sspitsyn/webrevs/2016/hotspot/8159145-jigsaw-jvmti-pkg.3/ 
>>>>>>
>>>>
>>>> Are there intended to be other callers of Module::get_named_module? 
>>>> If not it seems odd to go to all the trouble of throwing 
>>>> exceptions, just to have the caller clear them and return an error 
>>>> code. Or you could move all that argument checking code into the 
>>>> JVMTI function directly - if called internally you would just 
>>>> assert that arguments are as expected.
>>>>
>>>>
>>>> src/share/vm/prims/jvmti.xml
>>>>
>>>> +         otherwise the <code>NULL</code> is returned.
>>>>
>>>> Delete "the".
>>>>
>>>> Otherwise all looks good to me.
>>>>
>>>>>>
>>>>>>
>>>>>> The Jdk webrev is the same:
>>>>>>
>>>>>> http://cr.openjdk.java.net/~sspitsyn/webrevs/2016/hotspot/8159145-jigsaw-jvmti-pkg.jdk1/ 
>>>>>>
>>>>>
>>>>> Sorry, the Jdk webrev changed as well:
>>>>>
>>>>> http://cr.openjdk.java.net/~sspitsyn/webrevs/2016/hotspot/8159145-jigsaw-jvmti-pkg.jdk3/ 
>>>>>
>>>>
>>>> Looks fine.
>>>>
>>>> Thanks,
>>>> David
>>>>
>>>>>
>>>>> Thanks,
>>>>> Serguei
>>>>>
>>>>>
>>>>>>
>>>>>>
>>>>>> Summary:
>>>>>>
>>>>>>   This is the review round #3.
>>>>>>   Alan suggested to replace the function GetModuleByPackageName with
>>>>>> the GetNamedModule.
>>>>>>   New function will return NULL if the package is not in a module
>>>>>> defined to the class loader.
>>>>>>   It simplifies the API and makes it easier to specify.
>>>>>>   JVM TI agents that instrument code in named modules need the 
>>>>>> Module
>>>>>> at class load time.
>>>>>>
>>>>>>   One question that came from the function semantics change.
>>>>>>   I had to implement the Modules::get_named_module() from scratch
>>>>>> independently of the existing
>>>>>>   Modules::get_module_by_package_name() and Modules::get_module().
>>>>>>   The issue is that the Modules::get_module() can return the unnamed
>>>>>> module whereas the
>>>>>>   JVMTI helper Modules::get_named_module() should return NULL 
>>>>>> instead
>>>>>> of the unnamed module.
>>>>>>   Please, let me know if it is Ok or if you have better ideas how to
>>>>>> share the code.
>>>>>>
>>>>>>   This is the Summary from review round #1:
>>>>>>
>>>>>>   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.
>>>>>>
>>>>>>   It includes new jtreg test with native JVMTI agent.
>>>>>>
>>>>>>
>>>>>> Testing:
>>>>>>    Run newly developed jtreg test.
>>>>>>
>>>>>> Thanks,
>>>>>> Serguei
>>>>>
>>>
>>
>