On 27.03.2014 18:00, Peter Levart wrote:
On 03/27/2014 02:36 PM, Ivan Gerasimov wrote:
Thank you Peter!
There could be a little delay (say half the timeout: 500ms)
specified after main thread returns from the startedSignal.await();
and before setting referent = null; and doing System.gc(). This
would decrease the chance that the reference is enqueued before
EarlyTimeout threads enter queue.remove(1000), thus making the test
more reliable in failing with unpatched code.
Yes, you're right.
I've checked the test against jdk9-b01 (no fix for 6853696 yet).
It gives 2.5% of false negatives (i.e. in 5 out of 200 runs the
reference was enqueued before calling to remove()).
With an additional delay of TIMEOUT / 2 this number dropped to 0%.
With jdk9-b05 (with fix for 6853696) no false positives were shown
with or without this additional delay.
Now even if the referent is released and System.gc() is called, that
does not guarantee that a WeakReference is going to be enqueued
before the EarlyTimeout threads timeout and the result could as well
be 0 collected references. To increase the chance that the reference
is enqueued in a timely manner, main thread could, immediately after
System.gc(), call:
SharedSecrets.getJavaLangRefAccess().tryHandlePendingReference();
(since SharedSecrets is in sun.misc protected package,
JavaLangRefAccess instance would have to be obtained using
reflection unfortunately).
I would prefer not to complicate the test too much, if you don't
mind. I think the test already shows reliable reproducibility.
I suggest to return to the very first trivial fix:
http://cr.openjdk.java.net/~igerasim/8038333/1/webrev/
But this webrev *is moving startedSignal.await() after System.gc()* ...
Oops, sorry. It was meant to be /8038333/*0*/webrev/, of course!
Now, I updated the webrev with the additional delay as you suggested:
http://cr.openjdk.java.net/~igerasim/8038333/2/webrev/
Would you please have a look?
That looks good. So no warning if nonNullRefCount == 0 ... It is
probably not particularly useful if nobody is going to look at it, right?
Yeah.
I think that the test will only bring attention if it fails.
Regards, Peter
Sincerely yours,
Ivan
