[jira] [Created] (SPARK-4715) ShuffleMemoryManager.tryToAcquire may return a negative value

["Shixiong Zhu (JIRA)" <ji...@apache.org>]

Shixiong Zhu created SPARK-4715:
-----------------------------------

             Summary: ShuffleMemoryManager.tryToAcquire may return a negative value
                 Key: SPARK-4715
                 URL: https://issues.apache.org/jira/browse/SPARK-4715
             Project: Spark
          Issue Type: Bug
          Components: Spark Core
            Reporter: Shixiong Zhu


Here is a unit test to demonstrate it:

{code}
  test("threads should not be granted a negative size") {
    val manager = new ShuffleMemoryManager(1000L)
    manager.tryToAcquire(700L)

    val latch = new CountDownLatch(1)
    startThread("t1") {
       manager.tryToAcquire(300L)
      latch.countDown()
    }
    latch.await() // Wait until `t1` calls `tryToAcquire`

    val granted = manager.tryToAcquire(300L)
    assert(0 === granted, "granted is negative")
  }
{code}

It outputs "0 did not equal -200 granted is negative"



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