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

[Vladimir Kozlov]

It could be unsafe to check outside lock. method::_code is cleaned up under the same lock but after the state change. So 
if a caller access _code field it would be wrong.

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.

Thanks,
Vladimir K

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