On 1/16/14 8:38 PM, David Holmes wrote:
On 17/01/2014 1:31 PM, srikalyan chandrashekar wrote:
Hi David, the disassembled code is also attached to the bug. Per my
Sorry missed that.
analysis the exception was thrown when Reference Handler was on line 143
as put in the earlier email.
But if the numbers in the dissassembly match the BCI then 65 shows:
65: instanceof #11 // class sun/misc/Cleaner
which makes more sense, the runtime instanceof check might encounter
an OOME condition. I wish there was some easy way to trace into the
full call chain as TraceExceptions doesn't show you any runtime frames :(
Still, it is easy enough to check:
// Fast path for cleaners
boolean isCleaner = false;
try {
isCleaner = r instanceof Cleaner;
} catch (OutofMemoryError oome) {
continue;
}
Will get this into build and give a shot soon, in the log if you see bci
6 and bci 48 are where dispatch and uncaught exceptions are
raised(please correct me if i am wrong), i assumed its from
ReferenceHandler thread as it says the same thread Id 0x00007feed80cf800.
if (isCleaner) {
((Cleaner)r).clean();
continue;
}
Thanks,
David
--
Thanks
kalyan
On 1/16/14 6:16 PM, David Holmes wrote:
On 17/01/2014 4:48 AM, srikalyan wrote:
Hi David
On 1/15/14, 9:04 PM, David Holmes wrote:
On 16/01/2014 10:19 AM, srikalyan chandrashekar wrote:
Hi Peter/David, we could finally get a trace of exception with
fastdebug
build and ReferenceHandler modified (with runImpl() added and called
from run()). The logs, disassembled code is available in JIRA
<https://bugs.openjdk.java.net/browse/JDK-8022321> as attachments.
All I can see is the log for the OOMECatchingTest program not one for
the actual ReferenceHandler ??
Please search for ReferenceHandler in the log.
Observations from the log:
Root Cause:
1) UncaughtException is being dispatched from Reference.java:143
141 Reference<Object> r;
142 synchronized (lock) {
143 if (pending != null) {
144 r = pending;
145 pending = r.discovered;
146 r.discovered = null;
pending field in Reference is touched and updated by the
collector, so
at line 143 when the execution context is in Reference handler there
might have been an Exception pending due to allocation done by
collector
which causes ReferenceHandler thread to die.
Sorry but the GC does not trigger asynchronous exceptions so this
explanation does not make any sense to me. What part of the log led
you to this conclusion?
------------------ Log Excerpt begins ------------------
Exception <a 'java/lang/OutOfMemoryError'> (0x00000000ff7808e8)
thrown
[/home/srikalyc/work/ora2013/infracleanup/jdk8/hotspot/src/share/vm/gc_interface/collectedHeap.inline.hpp,
line 168]
for thread 0x00007feed80cf800
Exception <a 'java/lang/OutOfMemoryError'> (0x00000000ff7808e8)
thrown in interpreter method <{method} {0x00007feeddd3c600}
'runImpl'
'()V' in 'java/lang/ref/Reference$ReferenceHandler'>
at bci 65 for thread 0x00007feed80cf800
Exception <a 'java/lang/OutOfMemoryError'> (0x00000000ff7808e8)
thrown in interpreter method <{method} {0x00007feeddd3c478} 'run'
'()V' in 'java/lang/ref/Reference$ReferenceHandler'>
at bci 1 for thread 0x00007feed80cf800
Exception <a 'java/lang/OutOfMemoryError'> (0x00000000ff780868)
thrown
[/home/srikalyc/work/ora2013/infracleanup/jdk8/hotspot/src/share/vm/gc_interface/collectedHeap.inline.hpp,
line 157]
for thread 0x00007feed80cf800
Exception <a 'java/lang/OutOfMemoryError'> (0x00000000ff780868)
thrown in interpreter method <{method} {0x00007feeddcaaf90}
'uncaughtException' '(Ljava/lang/Thread;Ljava/lang/Throwable;)V' in '>
at bci 48 for thread 0x00007feed80cf800
Exception <a 'java/lang/OutOfMemoryError'> (0x00000000ff780868)
thrown in interpreter method <{method} {0x00007feeddca7298}
'dispatchUncaughtException' '(Ljava/lang/Throwable;)V' in 'java/lang/>
at bci 6 for thread 0x00007feed80cf800
------------------ Log Excerpt ends ------------------
Sorry if it is a wrong understanding.
What you are seeing there is an OOME escaping the run() method which
will cause the uncaughtExceptionHandler to be run which then triggers
a second OOME (likely as it tries to report information about the
first OOME). The first exception occurred in runImpl at BCI 65. Can
you disassemble (javap -c) the class you used so we can see what is at
BCI 65.
Thanks,
David
Suggested fix:
- As proposed earlier putting an outer guard(try-catch on OOME)
in the
ReferenceHandler will fix the issue, if ReferenceHandler is
considered
as part of the GC sub system then it should be alive even in the
midst
of an OOME so i feel that the additional guard should be allowed,
however i might still be ignorant of vital implications.
- Apart from the above changes, Peter's suggestion to create and
call a
private runImpl() from run() in ReferenceHandler makes sense to me.
Why would we need this?
David
-----
---
Thanks
kalyan
On 01/13/2014 03:57 PM, srikalyan wrote:
On 1/11/14, 6:15 AM, Peter Levart wrote:
On 01/10/2014 10:51 PM, srikalyan chandrashekar wrote:
Hi Peter the version you provided ran indefinitely(i put a 10
minute
timeout) and the program got interrupted(no error),
Did you run it with or without fastedbug & -XX:+TraceExceptions
? If
with, it might be that fastdebug and/or -XX:+TraceExceptions
changes
the execution a bit so that we can no longer reproduce the wrong
behaviour.
With fastdebug & -XX:TraceExceptions. I will try combination of
possible options(i.e without -XX:TraceEception on debug build etc)
soon.
even if there were to be an error you cannot print the
"string" of
thread to console(these have been attempted earlier).
...it has been attempted to print toString in uncaught exception
handler. At that time, the heap is still full. I'm printing it
after
the GC has cleared the heap. You can try that it works by
commenting
out the "try {" and corresponding "} catch (OOME x) {}" exception
handler...
Since there is a GC call prior to printing string i will give
that a
shot with non-debug build.
- The test's running on interpreter mode, what i am watching
for is
one error with trace. Without fastdebug build and
-XX:+TraceExceptions i am able to reproduce failure atleast 5
failures out of 1000 runs but with fastdebug+Trace no luck
yet(already past few 1000 runs).
It might be interesting to try with fastebug build but without the
-XX:+TraceExceptions option to see what has an effect on it. It
might
also be interesting to try the modified ReferenceHandler (the one
with private runImpl() method called from run()) and with normal
non-fastdebug JDK. This info might be useful when one starts to
inspect the exception handling code in interpreter...
Regards, Peter
--
Thanks
kalyan
Ph: (408)-585-8040
---
Thanks
kalyan
On 01/10/2014 02:57 AM, Peter Levart wrote:
On 01/10/2014 09:31 AM, Peter Levart wrote:
Since we suspect there's something wrong with exception
handling
in interpreter, I devised a hypothetical reproducer that
tries to
simulate ReferenceHandler in many aspects, but doesn't
require to
be a ReferenceHandler:
http://cr.openjdk.java.net/~plevart/misc/OOME/OOMECatchingTest.java
This is designed to run indefinitely and only terminate if/when
thread dies. Could you run this program in the environment that
causes the OOMEInReferenceHandler test to fail and see if it
terminates?
I forgot to mention that in order for this long-running
program to
exhibit interpreter behaviour, it should be run with -Xint
option.
So I suggest:
-Xmx24M -XX:-UseTLAB -Xint
Regards, Peter
