[9] RFR (XS): C2: continuous CallSite relinkage eventually disables compilation for a method

[Vladimir Ivanov]

>> I don't see how method::_code is relevant to compiled method state
>> checks. It's just a double-checked locking idiom. Should be safe since
>> state transitions are monotonic.
>>
>
> I think there is a path where AOT methods can become in-use again, so
> it's not completely monotonic.

Ok, I can leave the pre-lock check only for nmethods.

Best regards,
Vladimir Ivanov

>>> But, I think, it should be safe with your original change in
>>> CodeCache::make_marked_nmethods_not_entrant() because it does not access
>>> method::_code. You should use !is_not_entrant() instead of is_alive() -
>>> it works for AOT too.
>>
>> I decided to keep state checks both in
>> CodeCache::make_marked_nmethods_not_entrant() and
>> nmethod::make_not_entrant_or_zombie(). !is_not_entrant() isn't precise
>> enough, since it passes for zombie nmethods as well.
>>
>> Also, added equivalent pre-lock check in
>> AOTCompiledMethod::make_not_entrant_helper(). Let me know if you see
>> any problems with that.
>>
>> Best regards,
>> Vladimir Ivanov
>>
>>> On 1/26/17 12:44 PM, Vladimir Ivanov wrote:
>>>> What about moving the check to nmethod::make_not_entrant()?
>>>>
>>>> http://cr.openjdk.java.net/~vlivanov/8173338/webrev.01
>>>>
>>>> Or I can fix it separately.
>>>>
>>>> Best regards,
>>>> Vladimir Ivanov
>>>>
>>>> On 1/26/17 11:30 PM, Vladimir Kozlov wrote:
>>>>> It will not work for AOT nmethods which have not_used state.
>>>>>
>>>>> Vladimir
>>>>>
>>>>> On 1/26/17 8:47 AM, Vladimir Ivanov wrote:
>>>>>> http://cr.openjdk.java.net/~vlivanov/8173338/webrev.00/
>>>>>> https://bugs.openjdk.java.net/browse/JDK-8173338
>>>>>>
>>>>>> The fix for JDK-7177745 disabled deoptimization count update when it
>>>>>> happens due to CallSite.target change.
>>>>>>
>>>>>> There was one case missed though: the count is still updated when
>>>>>> compilation fails due to a dependency becoming invalid
>>>>>> during the compilation.
>>>>>>
>>>>>> The fix is to avoid the update when recompilation fails due to
>>>>>> call_site_target dependency failure.
>>>>>>
>>>>>> Also, added a check in CodeCache::make_marked_nmethods_not_entrant()
>>>>>> to avoid repeated nmethod::make_not_entrant() calls
>>>>>> on nmethods which are already not entrant. Otherwise, the check is
>>>>>> performed under Patching_lock inside
>>>>>> nmethod::make_not_entrant_or_zombie() for every non-entrant method in
>>>>>> the code cache.
>>>>>>
>>>>>> Testing: regression test, RBT (in progress)
>>>>>>
>>>>>> Thanks!
>>>>>>
>>>>>> Best regards,
>>>>>> Vladimir Ivanov
>