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

[Tobias Hartmann]

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
>>>
>