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  1. JDK
  2. JDK-8179954

AArch64: C1 and C2 volatile accesses are not sequentially consistent

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    • Bug
    • Status: Closed
    • P2
    • Resolution: Fixed
    • 8-aarch64, 9
    • 9
    • hotspot
    • b170
    • aarch64
    • Not verified

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      Description

        In C2 we use LDAR/STLR to handle volatile accesses, but in C1 and the interpreter we use separate DMB instructions and relaxed loads. When used together, these do not form a sequentially-consistent memory ordering. For example, if stores use STLR and loads use LDR;DMB a simple Dekker idiom will fail.

        This is extremely hard to test because the loads and stores have to be in separately-compiled methods, but it is incorrect, and likely to fail in very weakly-ordered implementations.

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                aph Andrew Haley
                aph Andrew Haley
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                  Updated:
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