A: 

Is the method recursive, somehow? Maybe you're using an object inside of it which requires that very same method?

Carl Seleborg  2008-12-03 10:02:59
I don't think it works that way, its not the method that holds the lock, its the thread...
Ape-inago  2008-12-03 18:38:50
A: 

but locks on synchronized methods are reentrant, which means that if a thread which holds the lock on that object tries to lock it again, it will always succeed.

pdeva  2008-12-03 10:04:37
A: 

Hi,

It might be worth trying a deadlock detecting bit of code - like this.

The stopQuery lock does not seem to have acquired the lock previously in the stack trace, but then that lock does not seem to have acquired anywhere else either - weird...

"Worker-2" prio=10 tid=0x00002aad1da66400 nid=0x5165 waiting for monitor entry [0x0000000041b43000..0x0000000041b43b90]
   java.lang.Thread.State: BLOCKED (on object monitor)
    at org.eclipse.jdt.internal.core.index.DiskIndex.stopQuery(DiskIndex.java)
    - waiting to lock <0x00002aacdfe83ea8> (a org.eclipse.jdt.internal.core.index.DiskIndex)
    at org.eclipse.jdt.internal.core.index.Index.stopQuery(Index.java:192)

There is a wait on a held lock in this bit, but thats released the lock until it gets a notify/timeout:

"Text Viewer Hover Presenter" daemon prio=10 tid=0x00002aad20166400 nid=0x51f4 in Object.wait() [0x000000004254c000..0x000000004254dd90]
   java.lang.Thread.State: WAITING (on object monitor)
    at java.lang.Object.wait(Native Method)
    - waiting on <0x00002aace2276720> (a java.lang.Object)
    at java.lang.Object.wait(Object.java:485)
    at org.eclipse.jdt.internal.ui.javaeditor.ASTProvider.getAST(ASTProvider.java:450)
    - locked <0x00002aace2276720> (a java.lang.Object)
    at org.eclipse.jdt.ui.SharedASTProvider.getAST(SharedASTProvider.java:129)
    at org.eclipse.jdt.internal.ui.text.java.hover.NLSStringHover.getHoverInfo(NLSStringHover.java:87)
    at org.eclipse.jdt.internal.ui.text.java.hover.AbstractJavaEditorTextHover.getHoverInfo2(AbstractJavaEditorTextHover.java:86)
    at org.eclipse.jdt.internal.ui.text.java.hover.BestMatchHover.getHoverInfo2(BestMatchHover.java:129)
    at org.eclipse.jdt.internal.ui.text.java.hover.JavaEditorTextHoverProxy.getHoverInfo2(JavaEditorTextHoverProxy.java:82)
    at org.eclipse.jface.text.TextViewerHoverManager$4.run(TextViewerHoverManager.java:166)
Chris Kimpton  2008-12-03 10:52:11
i did a deadlock check inside jconsole and came up with nothing.
pdeva  2008-12-03 12:23:54
A: 

Is it possible that DiskIndex.java has no line information? My guess is that you're hanging inside the method where it tries to acquire a completely different lock but you can't see that because there is no line information to display in the stack trace.

Aaron Digulla  2008-12-03 10:55:53
i tried putting a println inside stopQuery(). the call is never entered.
pdeva  2008-12-03 11:29:55
Okay. I don't see where the thread is acquiring the lock in the stack trace. I suggest that you get a dump of all monitors and check if the info you see above doesn't really mean "thread tries to lock". At first glance, I would agree with you but obviously, we're wrong or it wouldn't hang.
Aaron Digulla  2008-12-03 12:24:37
i dont get you.if it says 'blocked' that means that the thread is blocked waiting to lock the object.
pdeva  2008-12-03 14:11:25
We assume that the thread "Worker-2" must hold the lock based on the picture above. But since it would not block in this case, our assumption must be wrong.
Aaron Digulla  2008-12-03 14:53:47
+1  A: 

This looks like a particularly nasty deadlock. It's hard to tell for sure without a little more information. Here's what I see without the code in front of me, though:

Possible deadlock on (or at least contention for) Object reference 0x00002aace2276720 between "Text Viewer Hover Presenter" and "Worker-3" while "Worker-3" is holding the lock on reference 0x00002aace2276ad0.

This second reference seems to be the cause for a whole pile of blocked threads (specifically "Worker-4", "Worker-1" and "Worker-0").

My suggestion would be to check ASTProvider.java line 450 (see the stack trace for the first two where the suspicious object lock seems to be held but then doesn't seem to get past the wait()). I would also suggest try running the executable locked to a single core (assuming that this is a multicore system).

The next piece of code that looks like it's worth testing would be SelectionListenerWithASTManager.java line 153 (where reference 0x00002aace2276ad0 is locked, causing the Workers to block).

Lockers of 0x00002aace2276720:

"Text Viewer Hover Presenter" daemon prio=10 tid=0x00002aad20166400 nid=0x51f4 in Object.wait() [0x000000004254c000..0x000000004254dd90]
   java.lang.Thread.State: WAITING (on object monitor)
    at java.lang.Object.wait(Native Method)
    - waiting on <0x00002aace2276720> (a java.lang.Object)
    at java.lang.Object.wait(Object.java:485)
    at org.eclipse.jdt.internal.ui.javaeditor.ASTProvider.getAST(ASTProvider.java:450)
    - locked <0x00002aace2276720> (a java.lang.Object)
    at org.eclipse.jdt.ui.SharedASTProvider.getAST(SharedASTProvider.java:129)
    at org.eclipse.jdt.internal.ui.text.java.hover.NLSStringHover.getHoverInfo(NLSStringHover.java:87)
    at org.eclipse.jdt.internal.ui.text.java.hover.AbstractJavaEditorTextHover.getHoverInfo2(AbstractJavaEditorTextHover.java:86)
    at org.eclipse.jdt.internal.ui.text.java.hover.BestMatchHover.getHoverInfo2(BestMatchHover.java:129)
    at org.eclipse.jdt.internal.ui.text.java.hover.JavaEditorTextHoverProxy.getHoverInfo2(JavaEditorTextHoverProxy.java:82)
    at org.eclipse.jface.text.TextViewerHoverManager$4.run(TextViewerHoverManager.java:166)

"Worker-3" prio=10 tid=0x00002aad132c3800 nid=0x5166 in Object.wait() [0x0000000042249000..0x000000004224ab10]
   java.lang.Thread.State: WAITING (on object monitor)
    at java.lang.Object.wait(Native Method)
    - waiting on <0x00002aace2276720> (a java.lang.Object)
    at java.lang.Object.wait(Object.java:485)
    at org.eclipse.jdt.internal.ui.javaeditor.ASTProvider.getAST(ASTProvider.java:450)
    - locked <0x00002aace2276720> (a java.lang.Object)
    at org.eclipse.jdt.ui.SharedASTProvider.getAST(SharedASTProvider.java:129)
    at org.eclipse.jdt.internal.ui.viewsupport.SelectionListenerWithASTManager$PartListenerGroup.calculateASTandInform(SelectionListenerWithASTManager.java:168)
    at org.eclipse.jdt.internal.ui.viewsupport.SelectionListenerWithASTManager$3.run(SelectionListenerWithASTManager.java:153)
    - locked <0x00002aace2276ad0> (a java.lang.Object)
    at org.eclipse.core.internal.jobs.Worker.run(Worker.java:55)

Blocked on 0x00002aace2276ad0

"Worker-4" prio=10 tid=0x00002aad132c4000 nid=0x5167 waiting for monitor entry [0x000000004234b000..0x000000004234bc90]
   java.lang.Thread.State: BLOCKED (on object monitor)
    at org.eclipse.jdt.internal.ui.viewsupport.SelectionListenerWithASTManager$3.run(SelectionListenerWithASTManager.java:153)
    - waiting to lock <0x00002aace2276ad0> (a java.lang.Object)
    at org.eclipse.core.internal.jobs.Worker.run(Worker.java:55)

"Worker-1" prio=10 tid=0x00002aad12835800 nid=0x5164 waiting for monitor entry [0x0000000041a42000..0x0000000041a42a10]
   java.lang.Thread.State: BLOCKED (on object monitor)
    at org.eclipse.jdt.internal.ui.viewsupport.SelectionListenerWithASTManager$3.run(SelectionListenerWithASTManager.java:153)
    - waiting to lock <0x00002aace2276ad0> (a java.lang.Object)
    at org.eclipse.core.internal.jobs.Worker.run(Worker.java:55)

"Worker-0" prio=10 tid=0x00002aad11a0ac00 nid=0x5146 waiting for monitor entry [0x0000000041941000..0x0000000041941d90]
   java.lang.Thread.State: BLOCKED (on object monitor)
    at org.eclipse.jdt.internal.ui.viewsupport.SelectionListenerWithASTManager$3.run(SelectionListenerWithASTManager.java:153)
    - waiting to lock <0x00002aace2276ad0> (a java.lang.Object)
    at org.eclipse.core.internal.jobs.Worker.run(Worker.java:55)
Bob Cross  2008-12-03 18:27:48

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