<Sound Dev> [12] Review Request: 8207150 Clip.isRunning() may return true after Clip.stop() was called

[Sergey Bylokhov]

Hello, Audio Guru.

Please review the fix for jdk12.

Bug: https://bugs.openjdk.java.net/browse/JDK-8207150
Webrev: http://cr.openjdk.java.net/~serb/8207150/webrev.00

This bug was found by the test added in JDK-8202264, this test checks 
this sequence:
   clip.loop();
   clip.stop();
   delay(20 sec);
   //check that Audio thread was stopped.

The test fails because the thread was not stopped, the reason is that 
"autoclose" mechanics cannot stop the thread of the clip which is in 
"running" state. So the test can be simplified to:
   clip.loop();
   clip.stop();
   if(clip.isRunning()) BOOM();

The root cause description:
   The problem exists in our DirectAudioDevice implementation. Before we 
play the audio we have this check in write():
if (!isActive() && doIO) {
     setActive(true);
     setStarted(true);
}

And to stop the clip we have this:
synchronized(lock) {
     // need to set doIO to false before notifying the
     // read/write thread, that's why isStartedRunning()
     // cannot be used
     doIO = false;
     lock.notifyAll();
}
setActive(false);
setStarted(false);


Note that it is possible to get the next race.
1 write() -> if(doIO) is true
2 stop() -> doIO=false + setActive(false) + setStarted(false)
3 write() -> setActive(true) + setStarted(true)

After the fix the access to doIO and setActive/setStarted is done under 
the lock.

-- 
Best regards, Sergey.