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  1. JDK
  2. JDK-8034249

need more workarounds for suspend equivalent condition issue



    • b04
    • generic
    • generic



        This issue was discussed in the review thread for:

        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:

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


        > 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


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                sspitsyn Serguei Spitsyn
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