RFR: 8269934: RunThese24H.java failed with EXCEPTION_ACCESS_VIOLATION in java_lang_Thread::get_thread_status

[David Holmes]

On Wed, 28 Jul 2021 14:22:07 GMT, Thomas Stuefe <stuefe at openjdk.org> wrote:

>> If a thread is attaching via JNI and has not yet created its Thread object it can be caught in a ThreadSnapshot during a thread dump (VM_DumpThreads) of all threads**, and the threadObj() will be NULL, so we can't pass it to get_thread_status().
>> 
>> ** JMM dumpThreads API
>> 
>> The initial fix simply checks for a NULL threadObj() and reports thread status NEW in that case.
>> 
>> Alternatively we could filter the attaching thread out completely in VM_DumpThreads::doit by expanding:
>> 
>>       if (jt->is_exiting() ||
>>           jt->is_hidden_from_external_view())  {
>>         // skip terminating threads and hidden threads
>>         continue;
>>       }
>> 
>> to also check jt->is_attaching_via_jni().
>> 
>> Note that higher-level code already filters out ThreadSnapshots with NULL threadObj() anyway so we could go either way.
>> 
>> Testing: manual hacks - see bug report.
>>   - tier 1-3 sanity testing
>> 
>> Thanks,
>> David
>
> This looks good to me.
> 
> ..Thomas

Thanks for the reviews @tstuefe  and @dcubed-ojdk !

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PR: https://git.openjdk.java.net/jdk/pull/4921