RFR(xs): 8134749: SoftReferences declared dead too early

[Per Liden]

On 2015-08-31 20:27, Tom Benson wrote:
> Per,
> Also looks good to me.   I actually picked up both your changes, on the

Thanks Tom.

> off chance it might help with 8130261.  (That appears it may be a
> problem with 'last ditch' GCs, which free all soft refs.  Yes, a
> longshot, but I tried it anyway.  No help.)

I had a very quick look at 8130261, and I agree that it doesn't seem 
related to this. Btw, If you can provoke the issue with a debug build 
you might want to run with -XX:+VerifyOops to catch the bad oop as early 
as possible.

cheers,
/Per

>
> Tom
>
> On 8/31/2015 2:20 PM, Jon Masamitsu wrote:
>> Per,
>>
>> Change looks good.
>>
>> Could you please run some tests with your fix and
>> -XX:+UseDynamicNumberOfGCThreads and
>> -XX:+UseParallelGC threads?  UseDynamicNumberOfGCThreads sometimes moves
>> work among the queues to get them into queues that will be processed
>> by an active
>> GC worker.  Thanks.
>>
>> Jon
>>
>>
>> On 08/31/2015 07:15 AM, Per Liden wrote:
>>>
>>> Hi,
>>>
>>> While preparing a different patch I looked through the
>>> ReferenceProcessor and noticed what looks like a silent mistreatment
>>> of SoftReferences.
>>>
>>> Summary: RefProcPhase1Task uses WorkerThread::id() to select the list
>>> to process. After the recent changes to how WorkGang works[1], this
>>> no longer guarantees that all reference lists are processed. This in
>>> turn means we might kill SoftReferences even when the policy says
>>> they should be kept alive.
>>>
>>> The fix here would be to use the worker_id (named "i" in this code)
>>> passed into the Task's work() function instead of using
>>> WorkerThread::id().
>>>
>>>
>>> [1] There's no longer any guarantee that all GangWorker threads will
>>> execute the Task's work() function, since a quick-to-wakeup worker
>>> thread might steal the work intended for a slow-to-wakeup worker thread.
>>>
>>>
>>> Webrev: http://cr.openjdk.java.net/~pliden/8134749/webrev.0/
>>>
>>> Bug: https://bugs.openjdk.java.net/browse/JDK-8134749
>>>
>>> Testing: jprt
>>>
>>>
>>> Btw, I'll to send out a follow-up patch (JDK-8134744) which makes
>>> sure WorkerThread::id() and the worker_id always match to avoid this
>>> type of bugs in the future.
>>>
>>> /Per
>>
>