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

[David Holmes]

On Wed, 28 Jul 2021 10:03:10 GMT, David Holmes <dholmes 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

Still looking for a serviceability review please - @sspitsyn , @plummercj  ?

Thanks

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