[Bug 2154648] [NEW] Swing UI application freezes on blocked AWT EventQueue by PulseAudio Eventloop Thread

enyone 2154648 at bugs.launchpad.net
Sat May 30 18:44:37 UTC 2026 

Public bug reported:

Ubuntu 26.04 LTS

openjdk-8-jre:
  Installed: 8u492-ga~us2-0ubuntu1~26.04.1
  Candidate: 8u492-ga~us2-0ubuntu1~26.04.1

Implementation on
org.classpath.icedtea.pulseaudio.PulseAudioDataLine.close() calls
java.util.concurrent.Semaphore.acquire() that never returns causing
application GUI to freeze indefinitely caused originally by GUI button
mouse click.

"AWT-EventQueue-1" #14 prio=6 os_prio=0 tid=0x000078e0604b9800 nid=0x20c1 waiting on condition [0x000078e04c822000]
   java.lang.Thread.State: WAITING (parking)
        at sun.misc.Unsafe.park(Native Method)
        - parking to wait for  <0x00000000f1e02ce8> (a java.util.concurrent.Semaphore$NonfairSync)
        at java.util.concurrent.locks.LockSupport.park(LockSupport.java:175)
        at java.util.concurrent.locks.AbstractQueuedSynchronizer.parkAndCheckInterrupt(AbstractQueuedSynchronizer.java:836)
        at java.util.concurrent.locks.AbstractQueuedSynchronizer.doAcquireSharedInterruptibly(AbstractQueuedSynchronizer.java:997)
        at java.util.concurrent.locks.AbstractQueuedSynchronizer.acquireSharedInterruptibly(AbstractQueuedSynchronizer.java:1304)
        at java.util.concurrent.Semaphore.acquire(Semaphore.java:312)
        at org.classpath.icedtea.pulseaudio.PulseAudioDataLine.close(PulseAudioDataLine.java:307)
        at org.classpath.icedtea.pulseaudio.PulseAudioClip.close(PulseAudioClip.java:258)
        at ***.shared.models.Sound.Close(Sound.java:60)
        at ***.application.MainWindow.CloseButtonMouseClicked(MainWindow.java:1389)
        at ***.application.MainWindow.access$1700(MainWindow.java:90)
        at ***.application.MainWindow$18.mouseClicked(MainWindow.java:491)
        at java.awt.AWTEventMulticaster.mouseClicked(AWTEventMulticaster.java:270)
        at java.awt.Component.processMouseEvent(Component.java:6542)
        at javax.swing.JComponent.processMouseEvent(JComponent.java:3324)
        at java.awt.Component.processEvent(Component.java:6304)
        at java.awt.Container.processEvent(Container.java:2239)
        at java.awt.Component.dispatchEventImpl(Component.java:4889)
        at java.awt.Container.dispatchEventImpl(Container.java:2297)
        at java.awt.Component.dispatchEvent(Component.java:4711)
        at java.awt.LightweightDispatcher.retargetMouseEvent(Container.java:4904)
        at java.awt.LightweightDispatcher.processMouseEvent(Container.java:4544)
        at java.awt.LightweightDispatcher.dispatchEvent(Container.java:4476)
        at java.awt.Container.dispatchEventImpl(Container.java:2283)
        at java.awt.Window.dispatchEventImpl(Window.java:2746)
        at java.awt.Component.dispatchEvent(Component.java:4711)
        at java.awt.EventQueue.dispatchEventImpl(EventQueue.java:760)
        at java.awt.EventQueue.access$500(EventQueue.java:97)
        at java.awt.EventQueue$3.run(EventQueue.java:709)
        at java.awt.EventQueue$3.run(EventQueue.java:703)
        at java.security.AccessController.doPrivileged(Native Method)
        at java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(ProtectionDomain.java:74)
        at java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(ProtectionDomain.java:84)
        at java.awt.EventQueue$4.run(EventQueue.java:733)
        at java.awt.EventQueue$4.run(EventQueue.java:731)
        at java.security.AccessController.doPrivileged(Native Method)
        at java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(ProtectionDomain.java:74)
        at java.awt.EventQueue.dispatchEvent(EventQueue.java:730)
        at org.GNOME.Accessibility.AtkWrapper$6.dispatchEvent(AtkWrapper.java:744)
        at java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:205)
        at java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:116)
        at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:105)
        at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:101)
        at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:93)
        at java.awt.EventDispatchThread.run(EventDispatchThread.java:82)

$ cat /usr/lib/jvm/java-8-openjdk-amd64/jre/lib/sound.properties
javax.sound.sampled.Clip=org.classpath.icedtea.pulseaudio.PulseAudioMixerProvider
javax.sound.sampled.Port=org.classpath.icedtea.pulseaudio.PulseAudioMixerProvider
javax.sound.sampled.SourceDataLine=org.classpath.icedtea.pulseaudio.PulseAudioMixerProvider
javax.sound.sampled.TargetDataLine=org.classpath.icedtea.pulseaudio.PulseAudioMixerProvider

** Affects: openjdk-8 (Ubuntu)
     Importance: Undecided
         Status: New


** Tags: awt pulseaudio

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https://bugs.launchpad.net/bugs/2154648

Title:
  Swing UI application freezes on blocked AWT EventQueue by PulseAudio
  Eventloop Thread

Status in openjdk-8 package in Ubuntu:
  New

Bug description:
  Ubuntu 26.04 LTS

  openjdk-8-jre:
    Installed: 8u492-ga~us2-0ubuntu1~26.04.1
    Candidate: 8u492-ga~us2-0ubuntu1~26.04.1

  Implementation on
  org.classpath.icedtea.pulseaudio.PulseAudioDataLine.close() calls
  java.util.concurrent.Semaphore.acquire() that never returns causing
  application GUI to freeze indefinitely caused originally by GUI button
  mouse click.

  "AWT-EventQueue-1" #14 prio=6 os_prio=0 tid=0x000078e0604b9800 nid=0x20c1 waiting on condition [0x000078e04c822000]
     java.lang.Thread.State: WAITING (parking)
          at sun.misc.Unsafe.park(Native Method)
          - parking to wait for  <0x00000000f1e02ce8> (a java.util.concurrent.Semaphore$NonfairSync)
          at java.util.concurrent.locks.LockSupport.park(LockSupport.java:175)
          at java.util.concurrent.locks.AbstractQueuedSynchronizer.parkAndCheckInterrupt(AbstractQueuedSynchronizer.java:836)
          at java.util.concurrent.locks.AbstractQueuedSynchronizer.doAcquireSharedInterruptibly(AbstractQueuedSynchronizer.java:997)
          at java.util.concurrent.locks.AbstractQueuedSynchronizer.acquireSharedInterruptibly(AbstractQueuedSynchronizer.java:1304)
          at java.util.concurrent.Semaphore.acquire(Semaphore.java:312)
          at org.classpath.icedtea.pulseaudio.PulseAudioDataLine.close(PulseAudioDataLine.java:307)
          at org.classpath.icedtea.pulseaudio.PulseAudioClip.close(PulseAudioClip.java:258)
          at ***.shared.models.Sound.Close(Sound.java:60)
          at ***.application.MainWindow.CloseButtonMouseClicked(MainWindow.java:1389)
          at ***.application.MainWindow.access$1700(MainWindow.java:90)
          at ***.application.MainWindow$18.mouseClicked(MainWindow.java:491)
          at java.awt.AWTEventMulticaster.mouseClicked(AWTEventMulticaster.java:270)
          at java.awt.Component.processMouseEvent(Component.java:6542)
          at javax.swing.JComponent.processMouseEvent(JComponent.java:3324)
          at java.awt.Component.processEvent(Component.java:6304)
          at java.awt.Container.processEvent(Container.java:2239)
          at java.awt.Component.dispatchEventImpl(Component.java:4889)
          at java.awt.Container.dispatchEventImpl(Container.java:2297)
          at java.awt.Component.dispatchEvent(Component.java:4711)
          at java.awt.LightweightDispatcher.retargetMouseEvent(Container.java:4904)
          at java.awt.LightweightDispatcher.processMouseEvent(Container.java:4544)
          at java.awt.LightweightDispatcher.dispatchEvent(Container.java:4476)
          at java.awt.Container.dispatchEventImpl(Container.java:2283)
          at java.awt.Window.dispatchEventImpl(Window.java:2746)
          at java.awt.Component.dispatchEvent(Component.java:4711)
          at java.awt.EventQueue.dispatchEventImpl(EventQueue.java:760)
          at java.awt.EventQueue.access$500(EventQueue.java:97)
          at java.awt.EventQueue$3.run(EventQueue.java:709)
          at java.awt.EventQueue$3.run(EventQueue.java:703)
          at java.security.AccessController.doPrivileged(Native Method)
          at java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(ProtectionDomain.java:74)
          at java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(ProtectionDomain.java:84)
          at java.awt.EventQueue$4.run(EventQueue.java:733)
          at java.awt.EventQueue$4.run(EventQueue.java:731)
          at java.security.AccessController.doPrivileged(Native Method)
          at java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(ProtectionDomain.java:74)
          at java.awt.EventQueue.dispatchEvent(EventQueue.java:730)
          at org.GNOME.Accessibility.AtkWrapper$6.dispatchEvent(AtkWrapper.java:744)
          at java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:205)
          at java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:116)
          at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:105)
          at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:101)
          at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:93)
          at java.awt.EventDispatchThread.run(EventDispatchThread.java:82)

  $ cat /usr/lib/jvm/java-8-openjdk-amd64/jre/lib/sound.properties
  javax.sound.sampled.Clip=org.classpath.icedtea.pulseaudio.PulseAudioMixerProvider
  javax.sound.sampled.Port=org.classpath.icedtea.pulseaudio.PulseAudioMixerProvider
  javax.sound.sampled.SourceDataLine=org.classpath.icedtea.pulseaudio.PulseAudioMixerProvider
  javax.sound.sampled.TargetDataLine=org.classpath.icedtea.pulseaudio.PulseAudioMixerProvider

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