RFR(8u): 8038636, 8055008, 8156137: SIGSEGV in ReceiverTypeData::clean_weak_klass_links ...and 8057570.

[coleen.phillimore at oracle.com]

Hi Kevin, These changes look good.  It's nice to have the simpler 
version of the InstanceKlass::_previous_versions in jdk8.  There was a 
bug tail so there may be more changes after 8040237.  It's worth 
following through all the bugs to get something close to what we have in 
jdk9/10.  But this change looks good so far.

Thanks,
Coleen

On 11/13/17 1:08 PM, Kevin Walls wrote:
> Hi,
>
> I'd like to get a hotspot review of these backports from 9 to 8u. This 
> is mainly runtime territory but some of the history is from the 
> compiler side.
>
> webrev: http://cr.openjdk.java.net/~kevinw/8055008.8156137/webrev.00/
>
> The one we need is:
>
> 8156137: SIGSEGV in ReceiverTypeData::clean_weak_klass_links
> jbs: https://bugs.openjdk.java.net/browse/JDK-8156137
> 9 changeset: 
> http://hg.openjdk.java.net/jdk9/jdk9/hotspot/rev/882e8cda60b3
>
> The 9 changeset is short, just changing klass.cpp, but not possible in 
> 8 without additional work, so...
>
> 1.
>
> 8038636: speculative traps break when classes are redefined
> https://bugs.openjdk.java.net/browse/JDK-8038636
>
> 9 changeset: 
> http://hg.openjdk.java.net/jdk9/jdk9/hotspot/rev/a7784ddacbef
>
> 9 review thread: 
> http://mail.openjdk.java.net/pipermail/hotspot-compiler-dev/2014-April/013948.html 
> (in 9 since April 2014)
>
> That one imports cleanly into 8u.
>
>
> 2.
>
> With that imported, we need:
>
> 8055008:Clean up code that saves the previous versions of redefined 
> classes
> https://bugs.openjdk.java.net/browse/JDK-8055008
>
> 9 changeset: 
> http://hg.openjdk.java.net/jdk9/jdk9/hotspot/rev/e3fb51ae8d7d
>
> This is the change to stop using PreviousVersionNode and get an 
> InstanceKlass* from previous_versions().
>
>
> My webrev: http://cr.openjdk.java.net/~kevinw/8055008.8156137/webrev.00/
>
> ...is 8055008 and 8156137 in 8u. The klass.cpp change here is 
> 8156137.  The rest is 8055008, so I can commit them separately.
>
> 8156137 doesn't have its own test, but I have found if you get this 
> area wrong, the test runtime/RedefineObject crashes.
>
>
> Notes:
> For 8055008 there was a change in 
> src/share/vm/classfile/classLoaderData.cpp which is already in 8u.
>
> src/share/vm/classfile/metadataOnStackMark.cpp:
> +MetadataOnStackMark::MetadataOnStackMark(bool has_redefined_a_class) {
>
> The change is to stop using JvmtiExport::has_redefined_a_class() here 
> which is already in 8u at this point, but the param is already there 
> with a different name, so renamed as per 8055008.
>
> universe.cpp: had a change in 8055008 but following that there was:
>
> 8057570: RedefineClasses() tests fail 
> assert(((Metadata*)obj)->is_valid()) failed: obj is valid
> https://bugs.openjdk.java.net/browse/JDK-8057570
> 9 changeset: 
> http://hg.openjdk.java.net/jdk9/jdk9/hotspot/rev/479ed4234a9d
>
> ..this puts back a few lines in nmethod.cpp which 8055008 removed:
>
> + // Call function Method*, not embedded in these other places.
> + if (_method != NULL) f(_method);
>
> ..and in universe.cpp:
>
> + // Make the dependent methods not entrant (in VM_Deoptimize they are 
> made zombies)
> + CodeCache::make_marked_nmethods_not_entrant();
>
> ..and removes: CodeCache::make_marked_nmethods_zombies();
>
> My webrev takes these into account.
>
>
> Then there are 8038636's two follow-on bugs which I'd like to 
> follow-up in a separate thread.
> 8039960 is a test change
> 8040237: nsk/jvmti/RetransformClasses/retransform001 crashed the VM on 
> all platforms when run with with -server -Xcomp
> https://bugs.openjdk.java.net/browse/JDK-8040237
>
>
> Thanks!
> Kevin
>
>
>