On 05/06/2013 09:42 PM, Peter Levart wrote:
On 05/06/2013 05:03 PM, Alan Bateman wrote:
On 06/05/2013 09:02, Thomas Schatzl wrote:
:
Alan also mentioned something about instrumentation that can add memory
allocations basically anywhere.
As the reference handler code is plain java code, it will be
affected as
other java code.
I mentioned instrumentation on the off-chance that there was more to
this puzzle.
I think Peter is right and the allocation of the InterruptedException
seems to be the only place where OOME is possible in this code. Do
you know if these tests call Thread.interrupt on random threads
(maybe as a stress test)? It is possible to get a reference to the
Reference Handler thread via Thread.getAllStackTraces and a few other
APIs so maybe this what is going on. If the tests aren't calling
interrupt on random threads then it suggests to me that there is
something else going on, maybe there is a lurking VM bug.
In any case, it seems safe to catch/ignore OOME here. One of the
mails mentioned ThreadDeath and I don't know if want to expand the
scope of the patch. That seems a case where it should be like the
Cleaner and terminate the VM.
I mentioned ThreadDeath as another possibility, similar to
InterruptedException, that could cause OOME. OOME that would result
from unsuccessful allocation of ThreadDeath error object in victim
thread should not be ignored though. But it seems that JVM designers
have already taken care of that, because contrary to
InterruptedException the ThreadDeath error object is allocated in
thread executing Thread.stop() method and this instance is later
raised as exception in victim thread. So OOME in Object.wait() can
only be caused by unsuccessful allocation of InterruptedException and
nothing else. That was my final conclusion. ThreadDeath thrown in
ReferenceHandler thread should not be caught and ignored.
If anyone is stop()-ing ReferenceHandler thread then it should be
stopped. Speaking of that, if ThreadDeath is thrown in the middle of
Cleaner's thunk.run() processing, then the Cleaner will exit JVM. I
think ThreadDeath should be separately caught and re-thrown instead.
Regards, Peter
Regards, Peter
-Alan.
