(11) RFR (S) JDK-8205509: assert(_name_and_id != 0LL) failed: encountered a class loader null name and id

coleen.phillimore at oracle.com coleen.phillimore at oracle.com
Mon Jun 25 14:12:58 UTC 2018



Lois, This looks good!
Thanks,
Coleen

On 6/22/18 7:39 PM, Lois Foltan wrote:
> On 6/22/2018 7:28 PM, coleen.phillimore at oracle.com wrote:
>
>>
>> Lois,
>> This looks good!
>>
>> http://cr.openjdk.java.net/~lfoltan/bug_jdk8205509/webrev/src/hotspot/share/classfile/classLoaderData.cpp.udiff.html 
>>
>>
>>    if (!h_class_loader.is_null()) {
>>      _class_loader = _handles.add(h_class_loader());
>>    }
>>
>> + if (!h_class_loader.is_null()) {
>> + _class_loader_klass = h_class_loader->klass();
>> + }
>> +
>>
>> Can you put the _class_loader_klass under the if statement above it?
>>
>> + } else {
>> + return _class_loader_klass->external_name();
>>
>> Can you add short comment:  // May be called in a race before 
>> _name_and_id is initialized.
>>
>> Unfortunately, there isn't a good way to assert this (other than 
>> maybe a flag which would serve the same purpose as a null 
>> _name_and_id), and this code path is sensitive to safepoints because 
>> the link from class_loader to ClassLoaderData and the addition of 
>> ClassLoaderData to the CLDG needs to appear atomic.
> Hi Coleen,
>
> Thanks for the review, good comments.  They all have been addressed 
> and more testing is in progress.  See updated webrev at:
>
> http://cr.openjdk.java.net/~lfoltan/bug_jdk8205509.1/webrev/
>
> Lois
>
>>
>> Thanks for the speedy fix.
>> Coleen
>>
>> On 6/22/18 7:00 PM, Lois Foltan wrote:
>>> Please review the following change to address a hs-tier5 test 
>>> failure. The recent change for JDK-8202605 aggravated an existing 
>>> race condition within ClassLoaderDataGraph::add() where a given 
>>> class loader's ClassLoaderData structure is added to the 
>>> ClassLoaderDataGraph prior to full initialization of the CLD's 
>>> _class_loader_klass, _name and _name_and_id fields within 
>>> ClassLoaderData::initialize_name_and_klass.  To ensure that methods 
>>> loader_name() and loader_name_and_id() always provide a string for 
>>> the class loader name, the fix involved moving the field, 
>>> _class_loader_klass, to the ClassLoaderData's constructor where if 
>>> _name and/or _name_and_id fields are null, a reasonable 
>>> _class_loader_klass's external_name() can be provided.
>>>
>>> open webrev http://cr.openjdk.java.net/~lfoltan/bug_jdk8205509/webrev/
>>> bug link at https://bugs.openjdk.java.net/browse/JDK-8205509
>>>
>>> Testing: hs-tier(1-2), jdk-tier(1-3) complete
>>>                hs-tier3-5 in progress
>>>                --test-repeat 50 ran for tier1 platforms of test 
>>> jdk/java/lang/instrument/DaemonThread/TestDaemonThread.java
>>>
>>> Thanks,
>>> Lois
>>
>



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