Hello Sergey,
Thank you for review of this fix. Yes, I agree that 4 fields of
"DirectAudioDevice.DirectClip" class which you specified
("loopStartFrame", "loopEndFrame", "newFramePosition",
"clipBytePosition") are also not thread-safe and should be marked with
"volatile" modifier, though they are not directly related to this bug.
The second version of the fix, which addresses your remark, was created.
In the second version of the fix "volatile" modifier was added to the
next 8 fields of "DirectClip" class, all of which are accessed both from
"DirectClip.run()" method and other methods of this class: "audioData",
"frameSize", "m_lengthInFrames", "loopCount", "clipBytePosition",
"newFramePosition", "loopStartFrame", "loopEndFrame". Could you please
review the second version of the fix.
Webrev: http://cr.openjdk.java.net/~alitvinov/8168751/jdk9/webrev.01
Thank you,
Anton
On 1/19/2017 12:34 AM, Sergey Bylokhov wrote:
Hi, Anton.
Probably some other fields in the DirectClip should be marked as volatile? For
example loopStartFrame/loopEndFrame/ are used in the run() but assigned in the
setLoopPoints
() w/o any synchronization?(the same setFramePosition
+newFramePosition/clipBytePosition)
Hello,
Could you please review the following fix for the bug.
Bug: https://bugs.openjdk.java.net/browse/JDK-8168751
Webrev: http://cr.openjdk.java.net/~alitvinov/8168751/jdk9/webrev.00
The bug consists in the fact that after many repetitive sequential calls to the methods "loop()", "stop()" on
the same instance of "java.applet.AudioClip" at some moment two threads with the name "Direct Clip", which
play this "AudioClip" instance, are created and start existing in parallel, what makes the being played clip sound as
corrupted.
"Direct Clip" thread is represented by the instance variable "com.sun.media.sound.DirectAudioDevice.DirectClip.thread",
is created in the method "com.sun.media.sound.DirectAudioDevice.DirectClip.open()" and is stopped by assigning "null"
value to "DirectClip.thread" instance variable in the method
"com.sun.media.sound.DirectAudioDevice.DirectClip.implClose()".
THE DEFINED ROOT CAUSES OF THE BUG:
1. The fact that "DirectClip.thread" instance variable is not thread-safe. There is a possibility that null
value assigned to it in one thread through the former mentioned "DirectClip.implClose()" method does not
become visible for the running "Direct Clip" thread in the method "DirectClip.run()".
2. In the method "DirectClip.run()" not taking into account the fact that a new "Direct Clip" thread could have already been started and assigned to
"DirectClip.thread" instance variable after the call to "DirectClip.implClose()", by the moment when "DirectClip.thread" value is checked
for null in "DirectClip.run()" method, or by the moment when the previous "Direct Clip" thread is awakened and continues execution after the
following code block in "DirectClip.run()" from the file "jdk/src/java.desktop/share/classes/com/sun/media/sound/DirectAudioDevice.java".
1354 try {
1355 lock.wait();
1356 } catch(InterruptedException ie) {}
THE SOLUTION:
The solution is based on correction of the listed above 2 root causes of the
bug.
Thank you,
Anton
