[concurrency-interest] LinkedBlockingDeque deadlock?

Ariel Weisberg ariel at weisberg.ws
Wed Jul 8 18:57:55 EDT 2009


Hi,

> The poll()ing thread is blocked waiting for the internal lock, but
> there's
> no indication of any thread owning that lock. You're using an OpenJDK 6
> build ... can you try JDK7 ?

I got a chance to do that today. I downloaded JDK 7 from
http://www.java.net/download/jdk7/binaries/jdk-7-ea-bin-b63-linux-x64-02_jul_2009.bin
and was able to reproduce the problem. I have attached the stack trace
from running the 1.7 version. It is the same situation as before except
there are 9 execution sites running on each host. There are no threads
that are missing or that have been restarted. Foo Network thread
(selector thread) and Network Thread - 0 are waiting on
0x00002aaab43d3b28. I also ran with JDK 7 and 6 and LinkedBlockingQueue
and was not able to recreate the problem using that structure.

> I don't recall anything similar to this, but I don't know what version
> that
> OpenJDK6 build relates to.

The cluster is running on CentOS 5.3.
>[aweisberg at 3f ~]$ rpm -qi java-1.6.0-openjdk-1.6.0.0-0.30.b09.el5
>Name        : java-1.6.0-openjdk           Relocations: (not relocatable)
>Version     : 1.6.0.0                           Vendor: CentOS
>Release     : 0.30.b09.el5                  Build Date: Tue 07 Apr 2009 07:24:52 PM EDT
>Install Date: Thu 11 Jun 2009 03:27:46 PM EDT      Build Host: builder10.centos.org
>Group       : Development/Languages         Source RPM: java-1.6.0-openjdk-1.6.0.0-0.30.b09.el5.src.rpm
>Size        : 76336266                         License: GPLv2 with exceptions
>Signature   : DSA/SHA1, Wed 08 Apr 2009 07:55:13 AM EDT, Key ID a8a447dce8562897
>URL         : http://icedtea.classpath.org/
>Summary     : OpenJDK Runtime Environment
>Description :
>The OpenJDK runtime environment.

> Make sure you haven't missed any exceptions occurring in other threads.
There are no threads missing in the application (terminated threads are
not replaced) and there is a try catch pair (prints error and rethrows)
around the run loop of each thread. It is possible that an exception may
have been swallowed up somewhere.

>A small reproducible test case from you would be useful.
I am working on that. I wrote a test case that mimics the application's
use of the LBD, but I have not succeeded in reproducing the problem in
the test case. The app has a single thread (network selector) that polls
the LBD and several threads (ExecutionSites, and network threads that
return results from remote ExecutionSites) that offer results into the
queue. About 120k items will go into/out of the deque each second. In
the actual app the problem is reproducible but inconsistent. If I run on
my dual core laptop I can't reproduce it, and it is less likely to occur
with a small cluster, but with 6 nodes (~560k transactions/sec) the
problem will usually appear. Sometimes the cluster will run for several
minutes without issue and other times it will deadlock immediately.

Thanks,

Ariel

On Wed, 08 Jul 2009 05:14 +1000, "Martin Buchholz"
<martinrb at google.com> wrote:
>[+core-libs-dev]
>
>Doug Lea and I are (slowly) working on a new version of LinkedBlockingDeque.
>I was not aware of a deadlock but can vaguely imagine how it might happen.
>A small reproducible test case from you would be useful.
>
>Unfinished work in progress can be found here:
>http://cr.openjdk.java.net/~martin/webrevs/openjdk7/BlockingQueue/
>
>Martin

On Wed, 08 Jul 2009 05:14 +1000, "David Holmes"
<davidcholmes at aapt.net.au> wrote:
> 
> Ariel,
> 
> The poll()ing thread is blocked waiting for the internal lock, but
> there's
> no indication of any thread owning that lock. You're using an OpenJDK 6
> build ... can you try JDK7 ?
> 
> I don't recall anything similar to this, but I don't know what version
> that
> OpenJDK6 build relates to.
> 
> Make sure you haven't missed any exceptions occurring in other threads.
> 
> David Holmes
> 
> > -----Original Message-----
> > From: concurrency-interest-bounces at cs.oswego.edu
> > [mailto:concurrency-interest-bounces at cs.oswego.edu]On Behalf Of Ariel
> > Weisberg
> > Sent: Wednesday, 8 July 2009 8:31 AM
> > To: concurrency-interest at cs.oswego.edu
> > Subject: [concurrency-interest] LinkedBlockingDeque deadlock?
> >
> >
> > Hi all,
> >
> > I did a search on LinkedBlockingDeque and didn't find anything similar
> > to what I am seeing. Attached is the stack trace from an application
> > that is deadlocked with three threads waiting for 0x00002aaab3e91080
> > (threads "ExecutionSite: 26", "ExecutionSite:27", and "Network
> > Selector"). The execution sites are attempting to offer results to the
> > deque and the network thread is trying to poll for them using the
> > non-blocking version of poll. I am seeing the network thread never
> > return from poll (straight poll()). Do my eyes deceive me?
> >
> > Thanks,
> >
> > Ariel Weisberg
> >
> 


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