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  1. JDK
  2. JDK-8229422

Taskqueue: Outdated selection of weak memory model platforms

    Details

    • Type: Bug
    • Status: Resolved
    • Priority: P2
    • Resolution: Fixed
    • Affects Version/s: 11, 13, 14
    • Fix Version/s: 14
    • Component/s: hotspot
    • Subcomponent:
      gc
    • Resolved In Build:
      b13

      Description

      GenericTaskQueue<E, F, N>::pop_global currently uses "defined SPARC || defined IA32 || defined AMD64" to select platforms which are multi-copy-atomic and hence don't require a memory fence.
      This selection was introduced by JDK-8012144 (http://hg.openjdk.java.net/jdk8/jdk8/hotspot/rev/cd25d3be91c5) and is no longer up to date.
      s390 is unnecessarily treated as weak memory model platform.

      Background: GenericTaskQueue uses a memory access pattern which requires a full fence between two load accesses when four threads (or more) are involved on platforms which don't enforce the property called "multi-copy atomicity" (e.g. PPC64, arm).
      This was analyzed here:
      http://mail.openjdk.java.net/pipermail/hotspot-dev/2013-March/008848.html

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              • Assignee:
                mdoerr Martin Doerr
                Reporter:
                mdoerr Martin Doerr
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                • Created:
                  Updated:
                  Resolved: