RFR: 8217309: ZGC: Fix ZNMethodTable corruption
Per Liden
per.liden at oracle.com
Tue Jan 22 11:05:33 UTC 2019
On 1/22/19 11:34 AM, Stefan Karlsson wrote:
> Hi Per,
>
> On 2019-01-22 10:36, Per Liden wrote:
>> Calls to CollectedHeap::register_nmethod()/unregister_nmethod() should
>> be protected by the CodeCache_lock (when called outside of
>> safepoints). However, nmethod::make_unloaded() calls
>> CollectedHeap::unregister_nmethod() without this lock held, which can
>> corrupt the ZNMethodTable. Adding the lock is straight forward. The
>> rest of the patch adjusts ZNMethodTable::unregister_nmethod() to never
>> return false (which should never happen), adds the the proper asserts,
>> etc.
>>
>> Bug: https://bugs.openjdk.java.net/browse/JDK-8217309
>> Webrev: http://cr.openjdk.java.net/~pliden/8217309/webrev.0
>
> Looks good.
Thanks for reviewing Stefan.
>
> One thought about related code:
> while (_iter_table != NULL) {
> MutexUnlockerEx mu(CodeCache_lock, Mutex::_no_safepoint_check_flag);
> os::naked_short_sleep(1);
> }
>
> We might want to consider changing this into using wait/notify instead
> of unlocker/sleep.
Sounds like a good future enhancement.
/Per
>
> Thanks,
> StefanK
>
>>
>> Testing: Tier1-4 on all archs. Tier-1-7 on Linux/x86
>>
>> (I'll update the bug with the proper fix-request label, justification,
>> etc)
>>
>> /Per
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