RFR: 8217309: ZGC: Fix ZNMethodTable corruption

[Erik Österlund]

Hi Per,

Looks good.

Thanks,
/Erik

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
>
> 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