RFR (XS): 8200362: G1Mux2Closure should disable implicit oop verification

[Stefan Karlsson]

On 2018-03-29 11:02, Thomas Schatzl wrote:
> Hi Stefan,
> 
> On Thu, 2018-03-29 at 09:52 +0200, Stefan Johansson wrote:
>> Hi Thomas,
>>
>> On 2018-03-28 17:27, Thomas Schatzl wrote:
>>> Hi all,
>>>
>>>     can I have reviews for this small change that fixes some
>>> annoyance
>>> when debugging with G1?
>>>
>>> In particular, G1Mux2Closure is used by verification to verify and
>>> in
>>> case of error print out g1 specific error messages.
>>>
>>> However, since G1Mux2Closure is an OopClosure, it is actually
>>> wrapped
>>> by NoHeaderExtendedOopClosure in oop_iterate* calls.
>>> ExtendedOopClosure
>>> has its own verification that is very generic, and may trigger in
>>> the
>>> same situations as G1Mux2Closure.
>>>
>>> Disable this implicit verification for G1Mux2Closure so that we
>>> always
>>> get the g1 specific error messages.
>>>
>>> CR:
>>> https://bugs.openjdk.java.net/browse/JDK-8200362
>>> Webrev:
>>> http://cr.openjdk.java.net/~tschatzl/8200362/webrev/
>>
>> Nice change, always good to get detailed information. I think you
>> need
>> to change the code using the G1Mux2Closure as well. On line 666 in
>> heapRegion.cpp:
>>     G1Mux2Closure mux(&vl_cl, &vr_cl);
>>     obj->oop_iterate_no_header(&mux);
>> This should now be a normal oop_iterate(&mux) to make sure the right
>> verification is done.
> 
> Fixed. Also looked through other closures used for verification.
> 
> http://cr.openjdk.java.net/~tschatzl/8200362/webrev.0_to_1 (diff)
> http://cr.openjdk.java.net/~tschatzl/8200362/webrev.1 (full)

Looks good.

I like that we get rid of usages of oop_iterate_no_header. Maybe we 
should remove the other usages in G1, as a separate RFE.

StefanK

> 
> Thomas
>