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))

[David Holmes]

Hi Serguei,

Looks okay to me.

Minor nit: "use a vm-op for safety" is actually "use a vm-safepoint-op 
for safety". Not all VM ops need involve a safepoint.

David

On 4/02/2014 9:13 PM, 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/
>
>
> 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
>