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))

[serguei.spitsyn at oracle.com]

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