Hi Mandy, yes I ran with JTreg to simulate the failure, i will try the
UEH patch to see if it sheds some light and get back to you. Thanks for
the direction :)
--
Thanks
kalyan
Ph: (408)-585-8040
On 12/19/13, 8:33 PM, Mandy Chung wrote:
Hi Srikalyan,
Maybe you can get add an uncaught handler to see if you can get
any information. 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.
