[jira] [Created] (SPARK-4813) ContextWaiter didn't handle 'spurious wakeup'

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

Shixiong Zhu created SPARK-4813:
-----------------------------------

             Summary: ContextWaiter didn't handle 'spurious wakeup'
                 Key: SPARK-4813
                 URL: https://issues.apache.org/jira/browse/SPARK-4813
             Project: Spark
          Issue Type: Bug
          Components: Streaming
            Reporter: Shixiong Zhu


According to [javadocs|https://docs.oracle.com/javase/7/docs/api/java/lang/Object.html#wait(long)],
{quote}
A thread can also wake up without being notified, interrupted, or timing out, a so-called spurious wakeup. While this will rarely occur in practice, applications must guard against it by testing for the condition that should have caused the thread to be awakened, and continuing to wait if the condition is not satisfied. In other words, waits should always occur in loops, like this one:

     synchronized (obj) {
         while (<condition does not hold>)
             obj.wait(timeout);
         ... // Perform action appropriate to condition
     }
{quote}
`wait` should always occur in loops.

But now ContextWaiter.waitForStopOrError doesn't.
{code}
  def waitForStopOrError(timeout: Long = -1) = synchronized {
    // If already had error, then throw it
    if (error != null) {
      throw error
    }

    // If not already stopped, then wait
    if (!stopped) {
      if (timeout < 0) wait() else wait(timeout)
      if (error != null) throw error
    }
  }
{code}



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