ADDITIONAL SYSTEM INFORMATION :
MacBook / macOS 10.14.5 / jdk-11.0.3 and jdk-12.0.1


A DESCRIPTION OF THE PROBLEM :
On a certain apple hardware Robot.waitForIdle() may take 20 sec while normally it works about 20-40 ms.

This is not an issue of the specific machine as the issue is reproducible on at least two different MacBooks.
This is regression since jdk1.8.0_212 as Robot.waitForIdle() works ok with this jdk on the hardware (1) below.

Example of the hardware (1) where Robot.waitForIdle() works bad, stably taking 20 sec on jdk-11.0.3 and jdk-12.0.1:

  OS: macOS Mojave 10.14.5
  Model Name: MacBook Pro
  Model Identifier: MacBookPro11,5
  Processor Name: Intel Core i7
  Processor Speed: 2,5 GHz
  Number of Processors: 1
  Total Number of Cores: 4
  L2 Cache (per Core): 256 KB
  L3 Cache: 6 MB
  Hyper-Threading Technology: Enabled
  Memory: 16 GB
  Boot ROM Version: 192.0.0.0.0
  SMC Version (system): 2.30f2
  Serial Number (system): *
  Hardware UUID: *

Example of the hardware (2) where Robot.waitForIdle() works ok, about 20 ms, on the same jdk-11.0.3 and jdk-12.0.1:

  OS: macOS Mojave 10.14.5
  Model Name: MacBook Pro
  Model Identifier: MacBookPro15,1
  Processor Name: Intel Core i7
  Processor Speed: 2,6 GHz
  Number of Processors: 1
  Total Number of Cores: 6
  L2 Cache (per Core): 256 KB
  L3 Cache: 9 MB
  Hyper-Threading Technology: Enabled
  Memory: 16 GB
  Boot ROM Version: 220.260.171.0.0 (iBridge: 16.16.5200.0.0,0)
  Serial Number (system): *
  Hardware UUID: *

REGRESSION : Last worked in version 8u212

STEPS TO FOLLOW TO REPRODUCE THE PROBLEM :
Please compile and run the WaitForIdleTest.java:

<javac> WaitForIdleTest.java
<java> WaitForIdleTest

EXPECTED VERSUS ACTUAL BEHAVIOR :
EXPECTED -
Robot.waitForIdle() takes about 20 ms to complete on hardware (1) (with jdk1.8.0_212).

<jdk1.8.0_212.jdk>/Contents/Home/bin/java WaitForIdleTest
Robot.waitForIdle() eplased time: 16
ACTUAL -
Robot.waitForIdle() takes about 20 sec to complete on hardware (1) (with jdk-11.0.3 and jdk-12.0.1).

<jdk-11.0.3.jdk>/Contents/Home/bin/java WaitForIdleTest
Robot.waitForIdle() eplased time: 20033 ms

<jdk-12.0.1.jdk>/Contents/Home/bin/java WaitForIdleTest
Robot.waitForIdle() eplased time: 20034 ms

---------- BEGIN SOURCE ----------
import java.awt.*;

public class WaitForIdleTest {

    public static void main(String[] args) throws Exception {

        Robot robot = new Robot();

        Frame frame = new Frame();
        frame.setSize(100, 100);
        frame.setVisible(true);

        long start = System.currentTimeMillis();
        robot.waitForIdle();
        long end = System.currentTimeMillis();

        frame.dispose();

        long eplasedTime = end - start;
        System.out.println("Robot.waitForIdle() eplased time: " + eplasedTime + " ms");
    }
}
---------- END SOURCE ----------

FREQUENCY : always