This issue was discussed in the review thread for:
   https://bugs.openjdk.java.net/browse/JDK-8032223

The issue is important to fix as a part of the Test Stabilization project.

Please, see my reply to Dan below.


Thanks, Dan!
Some comments below.

On 2/4/14 7:48 AM, Daniel D. Daugherty wrote:
> On 2/4/14 4:13 AM, serguei.spitsyn@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/
>
> src/share/vm/prims/jvmtiEnvBase.hpp
> No comments.
>
> src/share/vm/prims/jvmtiEnv.cpp
> No comments beyond David's tweak to the comment.

Will fix it before push.

> For future work...
>
> Looks like these VM ops also need the liveness check on the
> target JavaThread:
>
> VM_GetOwnedMonitorInfo
> VM_GetStackTrace
>
> JvmtiEnv::GetStackTrace() looks like it has the same
> is_thread_fully_suspended() flaw...

I know about this.
There are even more issues:
  GetCurrentContendedMonitor
  GetOwnedMonitorStackDepthInfo
  NotifyFramePop

I'll check if we can use an existing bug to add this extra request.
Otherwise, will file new one.

Thanks,
Serguei

>
> Dan
>
>> 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