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  1. JDK
  2. JDK-8346175

[21u] juc cannot be woken up when using virtual thread

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    • Icon: Bug Bug
    • Resolution: Unresolved
    • Icon: P3 P3
    • None
    • 21
    • core-libs
    • None

    • 30 CPU cores.

      When using virtual thread, the juc unpark event may not be executed and the whole application will wait forever.

      I have constructed a simple testcase to emulate the situation.
      I put the two files in the test/jdk/java/lang/Thread/virtual/ and run jtreg test it. The fail rate is 13/30.

      I find that there may be a problem in ForkJoinPool.java.
      The `signalWork` may choose do nothing when (c >>> RC_SHIFT) >= pc. (In the testcase, 29 threads are pinned and one is free for doing some work.)
      And the one active thread which is in the first lines of the function `awaitWork` (before change the ctl) will not be signaled and choose to park.

        1. jcmd.log
          100 kB
        2. JucSyncNativeMethod.java
          4 kB
        3. JucSyncNativeMethod.jtr
          52 kB
        4. JucSyncNativeMethod-1.jtr
          48 kB
        5. JucSyncNativeMethod-2.jtr
          52 kB
        6. libJucSyncNativeMethod.c
          1 kB

            vklang Viktor Klang
            jwtang Jiawei Tang
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              Created:
              Updated: