RFR (XS) 6471769: Error: assert(_cur_stack_depth == count_frames(), "cur_stack_depth out of sync")

[Staffan Larsen]

Looks good!

Thanks,
/Staffan

On 1 feb 2014, at 03:58, serguei.spitsyn at oracle.com wrote:

> Please, review the fix for:
>  https://bugs.openjdk.java.net/browse/JDK-6471769
> 
> 
> Open webrev:
> http://cr.openjdk.java.net/~sspitsyn/webrevs/2014/hotspot/6471769-JVMTI-FRAME/
> 
> Summary:
> 
>  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 more generic 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 big 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.
> 
>  The webrev for review is a one-liner work around the 6280037 for the GetFrameCount().
> 
>  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 non-suspended target threads.
>  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 is 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 are covered by the 6471769.
> 
> 
> Testing:
>  In progress: nsk.jvmti, nsk.jdi, nsk.jdwp, impacted JTreg tests
> 
> 
> Thanks,
> Serguei
>