2-nd round RFR (S) 8032223: nsk/regression/b4663146 gets assert(SafepointSynchronize::is_at_safepoint() || JvmtiEnv::is_thread_fully_suspended(get_thread(), false, &debug_bits))

Daniel D. Daugherty daniel.daugherty at oracle.com
Tue Feb 4 07:48:10 PST 2014

On 2/4/14 4:13 AM, serguei.spitsyn at oracle.com wrote:
> Please, review the fix for:
>   https://bugs.openjdk.java.net/browse/JDK-8032223
> Open webrev:
> http://cr.openjdk.java.net/~sspitsyn/webrevs/2014/hotspot/8032223-JVMTI-FRAME.1/ 

     No comments.

     No comments beyond David's tweak to the comment.

For future work...

Looks like these VM ops also need the liveness check on the
target JavaThread:


JvmtiEnv::GetStackTrace() looks like it has the same
is_thread_fully_suspended() flaw...


> Summary:
>   This is the second round of review for this issue.
>   But it was decided that the JDK-8032223 must be used to cover it 
> instead of the JDK-6471769.
>   The 8032223 was initially closed as a dup of 6471769 but it has been 
> re-open now.
>   There is a general issue in the suspend equivalent condition mechanism:
>   Two subsequent calls to the JvmtiEnv::is_thread_fully_suspended() 
> may return different results:
>     - 1-st: true
>     - 2-nd: false
>   This suspend equivalent issue is covered by another bug:
>     https://bugs.openjdk.java.net/browse/JDK-6280037
>   The bug to fix in this review is a specific manifestation of the 
> 6280037
>   in the JVMTI GetFrameCount() that has a major impact on the SQE 
> nightly.
>   It is on the Test Stabilization radar as well as the 6280037.
>   There are many tests intermittently failing because of this.
>   I've also decided to fix the same issue in the JVMTI 
> GetFrameLocation() as well.
>   The JVMTI GetFrameCount() spec tells:
>     "If this function is called for a thread actively executing 
> bytecodes (for example,
>      not the current thread and not suspended), the information 
> returned is transient."
>   So, it is Ok to call the GetFrameCount() for the non-suspended 
> target thread.
>   To achieve safety, the frame count for non-suspended threads is 
> calculated at a safepoint.
>   It should be Ok and more safe to do the same for suspended threads 
> as well.
>   There should be no big performance impact because it is already on a 
> slow path.
>   It is still important to avoid safepointing when the target thread 
> is current.
>   The bug 6280037 should go out of the Test Stabilization radar 
> (remove the svc-nightly label)
>   as the most of the impacted tests must be covered by the 8032223.
> Testing:
>   In progress:
>     - nsk.jvmti, nsk.jdi, nsk.jdwp
>     - JTreg com/sun/jdi
> Thanks,
> Serguei

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