RFR (M) 8201556: Disallow reading oops in ClassLoaderData if unloading

[coleen.phillimore at oracle.com]

On 4/17/18 2:20 PM, Kim Barrett wrote:
>> On Apr 17, 2018, at 12:02 PM, coleen.phillimore at oracle.com wrote:
>>
>> Summary: Move class_loader oop to an OopHandle, and assert that holder is alive when getting class_loader.
>>
>> open webrev at http://cr.openjdk.java.net/~coleenp/8201556.01/webrev
>> bug link https://bugs.openjdk.java.net/browse/JDK-8201556
>>
>> Tested with mach5 tiers 1-7.
>>
>> Thanks,
>> Coleen
> ------------------------------------------------------------------------------
> src/hotspot/share/classfile/classLoaderData.hpp
>    86   static ClassLoaderData* add_to_graph(Handle class_laoder, bool anonymous);
>
> s/laoder/loader/

Thanks!
>
> ------------------------------------------------------------------------------
> src/hotspot/share/classfile/classLoaderData.hpp
>   411   Klass* class_loader_klass() const { return _class_loader_klass; }
>   412   Symbol* class_loader_name() const { return _class_loader_name; }
>
> Maybe assert that the member being read has been set, since the
> initialization happens sometime after construction.  Or will that
> maybe not work because of the annoying null-class-loader?

It's null if the class loader is null, so I can't really assert it.
>
> ------------------------------------------------------------------------------
> src/hotspot/share/classfile/classLoaderData.cpp
>   942               p2i(this), p2i((void *)_class_loader.ptr_raw()), loader_name());
>
> Why is there a (void*) cast on the class loader ptr?

It was there.  I've removed the cast and am recompiling it.
>
> ------------------------------------------------------------------------------
> src/hotspot/share/oops/klass.hpp
>   640   bool is_loader_alive(BoolObjectClosure* is_alive) const { return !class_loader_data()->is_unloading(); }
>
> Is this just so you can defer updating is_loader_alive callers to
> another RFE?

Yes, see (please review!) this RFR:

RFR (M) 8201537: Remove is_alive closure from Klass::is_loader_alive()

This one should be first, and I'll merge these two lines to remove the 
BoolObjectClosure.

Thanks!
Coleen
> ------------------------------------------------------------------------------
>