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

[Tobias Hartmann]

Hi Mikael,

thanks for the information, I didn't know that.

I will change the fix according to Albert's proposal.

Best,
Tobias

On 07.10.2014 13:35, Mikael Gerdin wrote:
> Hi Tobias,
>
> On 2014-10-07 13:03, 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.
>
> This is an unsafe operation which will lead to a deadlock.
> You _cannot_ mix taking a single lock object with and without
> _no_safepoint_check_flag!
>
> See
> https://bugs.openjdk.java.net/browse/JDK-8047290
>
> /Mikael
>
>>
>> Testing:
>> - Failing tests
>> - JPRT
>>
>> Thanks,
>> Tobias
>>
>> [1] https://bugs.openjdk.java.net/browse/JDK-8058737