[9] RFR(XS): 8059735: make_not_entrant_or_zombie sees zombies

[Tobias Hartmann]

Thanks, Vladimir.

Best,
Tobias

On 07.10.2014 18:29, Vladimir Kozlov wrote:
> Looks good.
>
> Thanks,
> Vladimir
>
> On 10/7/14 7:52 AM, Tobias Hartmann wrote:
>> Hi Albert,
>>
>> On 07.10.2014 15:21, Albert Noll wrote:
>>> Hi Tobias,
>>>
>>> On 10/07/2014 03:08 PM, Tobias Hartmann wrote:
>>>> Hi Albert,
>>>>
>>>> thanks for the review.
>>>>
>>>> On 07.10.2014 13:16, Albert Noll wrote:
>>>>> Hi Tobias,
>>>>>
>>>>> would it also work to check the state of the nmethod before calling
>>>>> make_zombie?
>>>>>
>>>>> if (nm->is_not_entrant()) {
>>>>>    nm->make_zombie()
>>>>> }
>>>>
>>>> Yes, regarding Mikael's comment, that is a better solution.
>>>>
>>>>> In any case, it would be nice the have a comment that explains why we
>>>>> should not enter a
>>>>> safpoint / have to do the extra check as described above.
>>>>
>>>> I changed the fix accordingly and added an additional comment. I also
>>>> moved the statistics/debugging code such that it is only executed if
>>>> the sweeper sets the nmethod to zombie.
>>>>
>>>> New webrev: http://cr.openjdk.java.net/~thartmann/8059735/webrev.01/
>>> I have one additional question. Do we need to hold the "CompiledIC_lock"
>>> when
>>> we call make_zombie()?
>>
>> No, we don't need to hold the lock for 'make_zombie()'. I narrowed the
>> scope of the lock:
>>
>> http://cr.openjdk.java.net/~thartmann/8059735/webrev.02/
>>
>> Thanks,
>> Tobias
>>
>>>
>>> Best,
>>> Albert
>>>
>>>> Thanks,
>>>> Tobias
>>>>
>>>>>
>>>>> Best,
>>>>> Albert
>>>>>
>>>>>
>>>>> On 10/07/2014 01:03 PM, Tobias Hartmann wrote:
>>>>>> Hi,
>>>>>>
>>>>>> please review the following patch.
>>>>>>
>>>>>> Bug: https://bugs.openjdk.java.net/browse/JDK-8059735
>>>>>> Webrev: http://cr.openjdk.java.net/~thartmann/8059735/webrev.00/
>>>>>>
>>>>>> Problem:
>>>>>> In 'NMethodSweeper::process_nmethod' a non-entrant nmethod is
>>>>>> processed and can be converted to zombie (line 549 of
>>>>>> sweeper.cpp). To
>>>>>> clean the IC stubs of that nmethod [1] we acquire the CompiledIC_lock
>>>>>> and check for a safepoint. In this case, there is a safepoint request
>>>>>> and we block. During the safepoint a VM_Deoptimize operation is
>>>>>> executed (due to classloading) and the non-entrant nmethod is set to
>>>>>> zombie by 'CodeCache::make_marked_nmethods_zombies'. After the
>>>>>> safepoint the sweeper continues and tries to set the nmethod to
>>>>>> zombie
>>>>>> again.
>>>>>>
>>>>>> Solution:
>>>>>> Use a MutexLockerEx with the '_no_safepoint_check_flag' to acquire
>>>>>> the
>>>>>> CompiledIC_lock.
>>>>>>
>>>>>> Testing:
>>>>>> - Failing tests
>>>>>> - JPRT
>>>>>>
>>>>>> Thanks,
>>>>>> Tobias
>>>>>>
>>>>>> [1] https://bugs.openjdk.java.net/browse/JDK-8058737
>>>>>
>>>