[concurrency-interest] Potential threads getting stuck on WAITING(parking) in ReentrantLock

Rafael Brandão rblcin at gmail.com
Mon Jun 2 23:21:21 EDT 2014


I can also reproduce this issue with java version "1.7.0_60": Java(TM) SE
Runtime Environment (build 1.7.0_60-b19) and Java HotSpot(TM) 64-Bit Server
VM (build 24.60-b09, mixed mode). It could be that bug then, thanks David.
:-)

I still find it weird how I can only reproduce this issue with my
ReentrantLock and not with the default ReentrantLock so far. If I
understood correctly this was a problem on AQS, so in theory I should get
stuck using the default ReentrantLock as well.

Thanks for your help!

Best regards,
Rafael


On Mon, Jun 2, 2014 at 11:35 PM, David Holmes <davidcholmes at aapt.net.au>
wrote:

>  Hi Rafael,
>
> Can you try Oracle JDK 7? This might be:
>
> https://bugs.openjdk.java.net/browse/JDK-7011859
>
> which was fixed in 8.
>
> David
>
> -----Original Message-----
> *From:* concurrency-interest-bounces at cs.oswego.edu [mailto:
> concurrency-interest-bounces at cs.oswego.edu]*On Behalf Of *Rafael Brandão
> *Sent:* Tuesday, 3 June 2014 11:44 AM
> *To:* Dr Heinz M. Kabutz
> *Cc:* concurrency-interest at cs.oswego.edu; dholmes at ieee.org
> *Subject:* Re: [concurrency-interest] Potential threads getting stuck on
> WAITING(parking) in ReentrantLock
>
> Hello,
>
> David, I have now tested it with java version "1.8.0_05", Java(TM) SE
> Runtime Environment (build 1.8.0_05-b13) and Java HotSpot(TM) 64-Bit Server
> VM (build 25.5-b02, mixed mode). The problem with my nearly unmodified
> ReentrantLock getting stuck is no longer happening when I run the
> experiment. Would you also like me to test with any particular version?
> Thanks for the tip! Now about StackOverflowError, I don't see how it could
> be possible (I've posted a link to the code if you want to check), since
> there's no infinite recursion for example and each test run is relatively
> low in used resources.
>
> Heinz, I have posted the code on https://github.com/rafaelbrandao/msc -
> the latest commit message (it only has 3 commits) contains information on
> how to reproduce this issue. It seems to be fixed when I use Oracle JDK 8
> however.
>
> What could be causing the stuck threads? Is it possible this is a problem
> with the ReentrantLock algorithm/implementation?
>
> Best regards,
> Rafael
>
> On Sun, Jun 1, 2014 at 2:07 AM, Dr Heinz M. Kabutz <
> heinz at javaspecialists.eu> wrote:
>
>> Please send us a link to your code, both your ReentrantLock and the test
>> code?
>>
>> On 01/06/2014, David Holmes <davidcholmes at aapt.net.au> wrote:
>> > Hi Rafael,
>> >
>> > Does this reproduce with Oracle JDK or only the IcedTea distributions?
>> >
>> > The most likely issue is the StackOverflowError. Have excluded that
>> > possibility?
>> >
>> > David
>> >   -----Original Message-----
>> >   From: concurrency-interest-bounces at cs.oswego.edu
>> > [mailto:concurrency-interest-bounces at cs.oswego.edu]On Behalf Of Rafael
>> > Brandão
>> >   Sent: Sunday, 1 June 2014 8:50 AM
>> >   To: concurrency-interest at cs.oswego.edu
>> >   Subject: [concurrency-interest] Potential threads getting stuck on
>> > WAITING(parking) in ReentrantLock
>> >
>> >
>> >   Hello,
>> >
>> >
>> >   I'm working on a few changes for ReentrantLock to make A/B tests
>> between
>> > the original implementation and my modifications, so my first step was
>> to
>> > copy the sources of ReentrantLock, AbstractQueuedSynchronizer (shortly
>> AQS)
>> > and AbstractOwnableSynchronizer and put them in a different package.
>> After
>> > resolving basic compilation issues, I've found the issue with Unsafe
>> usage
>> > (insecurity exception) and I've solved it based on the article found in
>> [1].
>> > So basically my ReentrantLock has nothing different from the original
>> except
>> > for how I get the Unsafe in AQS.
>> >
>> >
>> >   After that, I've exhaustively conducted the following experiment: 200
>> > threads try to increment 1000 times each some integer counter protected
>> by
>> > explicit locks. There are 10 counters, so each counter has 20 threads
>> > concurrently trying to increment it. The main thread spawns all those
>> > threads and then wait for them with join method. Once I've ran this
>> > experiment many times (about 30000), it consistently get stuck in a
>> join for
>> > some thread when I use my almost unmodified ReentrantLock before 2000th
>> > attempt.
>> >
>> >
>> >   I've got the thread stacks in [2] and what I understood from it is
>> that
>> > the remaining threads are all stuck waiting for the lock to be released.
>> > However I've managed to print the owner of that lock and I see it's
>> unlocked
>> > and has no owner:
>> >
>> >
>> >     stuck thread state: WAITING
>> >     thread waiting lock: safe.ReentrantLock at 68a6a21a[Unlocked]
>> >     lock owner: null
>> >
>> >
>> >   I've been trying to reproduce it with the original ReentrantLock but I
>> > didn't get stuck so far. So I'm here to ask you if there's a known
>> issue on
>> > ReentrantLock that could cause this situation (and also be extremely
>> > unlikely to happen) or if there's something obvious that I should know
>> about
>> > the Unsafe usage given it's the only thing changed so far.
>> >
>> >
>> >   I suspect I have some disadvantage given that my nearly unmodified
>> class
>> > is not already compiled in the JVM (I could try to build the JDK
>> later), but
>> > this could only be a sign that the issue already exists in the code but
>> can
>> > only become more likely to happen in a slower implementation. I've also
>> > searched for related bugs and the closest thing I've found was [3].
>> >
>> >
>> >   I'm using a Intel(R) Core(tm) i7-3632QM notebook running Ubuntu
>> 12.04. Java
>>  > version is "1.7.0_55" and I'm using OpenJDK Runtime Environment
>> (IcedTea
>> > 2.4.7) (7u55-2.4.7-1ubuntu1~0.12.04.2) and OpenJDK 64-Bit Server VM
>> (build
>> > 24.51-b03, mixed mode). I've experienced this issue after copying
>> sources of
>> > jdk7u, jdk8u and jdk9.
>> >
>> >
>> >
>> >
>> >   Best regards,
>> >   Rafael
>> >
>> >
>> >
>> >
>> >   [1]
>> http://howtodoinjava.com/2013/10/19/usage-of-class-sun-misc-unsafe/
>> >   [2] https://gist.github.com/rafaelbrandao/4ec5f2cd272c4b8b183a
>> >   [3] https://bugs.openjdk.java.net/browse/JDK-8028686
>> >
>> >
>> >   --
>> >   Rafael Brandão @ CIn - Center of Informatics
>>
>>
>> --
>> Dr Heinz M. Kabutz (PhD CompSci)
>> Author of "The Java(tm) Specialists' Newsletter"
>> Sun/Oracle Java Champion 2005-2013
>> JavaOne Rockstar Speaker 2012
>> http://www.javaspecialists.eu
>> Tel: +30 69 75 595 262
>> Skype: kabutz
>>
>
>
>
> --
> Rafael Brandão @ CIn - Center of Informatics
>
>


-- 
Rafael Brandão @ CIn - Center of Informatics
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