On 20 Dec 2013, at 04:33, Mandy Chung <[email protected]> wrote:
> Hi Srikalyan,
>
> Maybe you can get add an uncaught handler to see if you can get
> any information.
+1. With this, at least the next time we see this failure we should have a
better idea where the OOM is coming from.
-Chris.
> I ran it for 1000 times but not able to duplicate
> the failure. Did you run it with jtreg (I didn't)?
>
> Below is the patch to install a thread's uncaught handler that
> you can take and try.
>
> diff --git a/test/java/lang/ref/OOMEInReferenceHandler.java
> b/test/java/lang/ref/OOMEInReferenceHand
> ler.java
> --- a/test/java/lang/ref/OOMEInReferenceHandler.java
> +++ b/test/java/lang/ref/OOMEInReferenceHandler.java
> @@ -51,6 +51,14 @@
> return first;
> }
>
> + static class UEH implements Thread.UncaughtExceptionHandler {
> + public void uncaughtException(Thread t, Throwable e) {
> + System.err.println("ERROR: " + t.getName() + " exception " +
> + e.getMessage());
> + e.printStackTrace();
> + }
> + }
> +
> public static void main(String[] args) throws Exception {
> // preinitialize the InterruptedException class so that the
> reference handler
> // does not die due to OOME when loading the class if it is the
> first use
> @@ -77,6 +85,8 @@
> throw new IllegalStateException("Couldn't find Reference Handler
> thread.");
> }
>
> + referenceHandlerThread.setUncaughtExceptionHandler(new UEH());
> +
> ReferenceQueue<Object> refQueue = new ReferenceQueue<>();
> Object referent = new Object();
> WeakReference<Object> weakRef = new WeakReference<>(referent,
> refQueue);
>
> On 12/19/2013 6:57 PM, srikalyan chandrashekar wrote:
>> Hi David Thanks for your comments, the unguarded part(clean and enqueue) in
>> the Reference Handler thread does not seem to create any new objects, so it
>> is the application(the test in this case) which is adding objects to heap
>> and causing the Reference Handler to die with OOME. I am still unsure about
>> the side effects of the code change and agree with your thoughts(on memory
>> exhaustion test's reliability).
>>
>> PS: hotspot dev alias removed from CC.
>>
>> --
>> Thanks
>> kalyan
>>
>> On 12/19/13 5:08 PM, David Holmes wrote:
>>> Hi Kalyan,
>>>
>>> This is not a hotspot issue so I'm moving this to core-libs, please drop
>>> hotspot from any replies.
>>>
>>> On 20/12/2013 6:26 AM, srikalyan wrote:
>>>> Hi all, I have been working on the bug JDK-8022321
>>>> <https://bugs.openjdk.java.net/browse/JDK-8022321> , this is a sporadic
>>>> failure and the webrev is available here
>>>> http://cr.openjdk.java.net/~srikchan/Regression/JDK-8022321_OOMEInReferenceHandler-webrev/
>>>>
>>>
>>> I'm really not sure what to make of this. We have a test that triggers an
>>> out-of-memory condition but the OOME can actually turn up in the
>>> ReferenceHandler thread causing it to terminate and the test to fail. We
>>> previously accounted for the non-obvious occurrences of OOME due to the
>>> Object.wait and the possible need to load the InterruptedException class -
>>> but still the OOME can appear where we don't want it. So finally you have
>>> just placed the whole for(;;) loop in a try/catch(OOME) that ignores the
>>> OOME. I'm certain that makes the test happy, but I'm not sure it is really
>>> what we want for the ReferenceHandler thread. If the OOME occurs while
>>> cleaning, or enqueuing then we will fail to clean and/or enqueue but there
>>> would be no indication that has occurred and I think that is a bigger
>>> problem than this test failing.
>>>
>>> There may be no way to make this test 100% reliable. In fact I'd suggest
>>> that no memory exhaustion test can be 100% reliable.
>>>
>>> David
>>>
>>>> *
>>>> **"Root Cause:Still not known"*
>>>> 2 places where there is a possibility for OOME
>>>> 1) Cleaner.clean()
>>>> 2) ReferenceQueue.enqueue()
>>>>
>>>> 1) The cleanup code in turn has 2 places where there is potential for
>>>> throwing OOME,
>>>> a) thunk Thread which is run from clean() method. This Runnable is
>>>> passed to Cleaner and appears in the following classes
>>>> java/nio/DirectByteBuffer.java
>>>> sun/misc/Perf.java
>>>> sun/nio/fs/NativeBuffer.java
>>>> sun/nio/ch/IOVecWrapper.java
>>>> sun/misc/Cleaner/ExitOnThrow.java
>>>> However none of the above overridden implementations ever create an
>>>> object in the clean() code.
>>>> b) new PrivilegedAction created in try catch Exception block of
>>>> clean() method but for this object to be created and to be held
>>>> responsible for OOME an Exception(other than OOME) has to be thrown.
>>>>
>>>> 2) No new heap objects are created in the enqueue method nor anywhere in
>>>> the deep call stack (VM.addFinalRefCount() etc) so this cannot be a
>>>> potential cause.
>>>>
>>>> *Experimental change to java.lang.Reference.java* :
>>>> - Put one more guard (try catch with OOME block) in the Reference
>>>> Handler Thread which may give the Reference Handler a chance to cleanup.
>>>> This is fixing the test failure (several 1000 runs with 0 failures)
>>>> - Without the above change the test fails atleast 3-5 times for every
>>>> 1000 run.
>>>>
>>>> *PS*: The code change is to a very critical part of JDK and i am fully
>>>> not aware of the consequences of the change, hence seeking expert help
>>>> here. Appreciate your time and inputs towards this.
>>>>
>>
>
