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Created attachment 162691 [details] hanged-jvm.txt Unfortunately it is a commons case for me when NetBeans just freezes while debugging. Typical use-case is - first symptom - NB stops evaluating variables in Watch window - I see endless messages "Evaluating..." instead of variable values - after some time - NB completely freezes - UI is not updated After I kill target process (the one being debugged), NB starts working normally. This way debugging becomes a nightmare - to resolve the problem i have to restart application many times hoping that NB will not freeze at most needed place :(. Problem most frequently reproduces when debugging one instance of NetBeans from another instance of NetBeans. I've generated thread dump for the last occurrence of that problem. I see nothing special except thread "AWT-EventQueue-0" is always waiting in the same place. Full dump is attached. Taking into consideration that after killing target process debugger-NB goes back to life - I think that something in 'debugger' functionality somehow blocks UI events and after breaking the debugger channel this block is automatically removed. "AWT-EventQueue-0" #22 prio=6 os_prio=0 tid=0x5cede800 nid=0x1d78 waiting on condition [0x5f0cd000] java.lang.Thread.State: WAITING (parking) at sun.misc.Unsafe.park(Native Method) - parking to wait for <0x06507480> (a java.util.concurrent.locks.AbstractQueuedSynchronizer$ConditionObject) at java.util.concurrent.locks.LockSupport.park(LockSupport.java:175) at java.util.concurrent.locks.AbstractQueuedSynchronizer$ConditionObject.await(AbstractQueuedSynchronizer.java:2039)
Can you please provide the NetBeans build number that you're using? There was issue #262424 which could cause similar symptoms, but it's fixed in 8.2. In the attachment it does not look like a deadlock, AWT is waiting for events. It has just opened a breakpoint customizer. Please check whether the customizer dialog is not mistakenly opened behind the NetBeans window - in this case NetBeans window would not be accepting events and would look like frozen.
I'm using NB 8.2 to debug NB built from local sources. Yes - there is no 'classic' deadlock logged in thread dump, but it may be a deadlock across two processes - i.e. AWT thread in debugger is blocked by something that waits for some in target debuggee process, what in turn waits for something else back in debugger process. I think I need to generated thread dump for both processes next time it occurs. Regarding mentioned "issue #262424" - I have another similar common buggy case - targed debugged partially stops during debugging, i.e. stepping through code does work but it seems like not all threads in target process are resumed - some of the typical observations - after I click "Continue (F5)" WEB request to target server still hangs until I completely detach debugger. (target process in my case is Karaf/OSGI with plenty of modules and with around 300 threads)
It also happens to me when I debug web apps with tomcat 8.0.27. When I kill tomcat , debugging stop and NB stops freezing