[9] RFR(S): 8029443: 'assert(klass->is_loader_alive(_is_alive)) failed: must be alive' during VM_CollectForMetadataAllocation

[Tobias Hartmann]

Sorry, forgot to answer this question:
> Were you able to create a small test case for it that would be useful 
> to add?
Unfortunately I was not able to create a test. The bug only reproduces 
on a particular system with a > 30 minute run of runThese.

Best,
Tobias

On 16.07.2014 09:54, Tobias Hartmann wrote:
> Hi Coleen,
>
> thanks for the review.
>> *+           if (csc->is_call_to_interpreted() && 
>> stub_contains_dead_metadata(is_alive, csc->destination())) {*
>> *+             csc->set_to_clean();*
>> *+           }*
>>
>> This appears in each case.  Can you fold it and the new function into 
>> a function like clean_call_to_interpreted_stub(is_alive, csc)?
>
> I folded it into the function clean_call_to_interpreter_stub(..).
>
> New webrev: http://cr.openjdk.java.net/~thartmann/8029443/webrev.01/
>
> Thanks,
> Tobias
>
>>
>> Thanks,
>> Coleen
>>
>>>
>>> So before the permgen removal embedded method* were oops and they 
>>> were processed in relocInfo::oop_type loop.
>>>
>>> May be instead of specializing opt_virtual_call_type and 
>>> static_call_type call site you can simple add a loop for 
>>> relocInfo::metadata_type (similar to oop_type loop)?
>>>
>>> Thanks,
>>> Vladimir
>>>
>>> On 7/14/14 4:56 AM, Tobias Hartmann wrote:
>>>> Hi,
>>>>
>>>> please review the following patch for JDK-8029443.
>>>>
>>>> Bug: https://bugs.openjdk.java.net/browse/JDK-8029443
>>>> Webrev: http://cr.openjdk.java.net/~thartmann/8029443/webrev.00/
>>>>
>>>> *Problem*
>>>> After the tracing/marking phase of GC, nmethod::do_unloading(..) 
>>>> checks
>>>> if a nmethod can be unloaded because it contains dead oops. If class
>>>> unloading occurred we additionally clear all ICs where the cached
>>>> metadata refers to an unloaded klass or method. If the nmethod is not
>>>> unloaded, nmethod::verify_metadata_loaders(..) finally checks if all
>>>> metadata is alive. The assert in CheckClass::check_class fails because
>>>> the nmethod contains Method* metadata corresponding to a dead Klass.
>>>> The Method* belongs to a to-interpreter stub [1] of an optimized
>>>> compiled IC. Normally we clear those stubs prior to verification to
>>>> avoid dangling references to Method* [2], but only if the stub is 
>>>> not in
>>>> use, i.e. if the IC is not in to-interpreted mode. In this case the
>>>> to-interpreter stub may be executed and hand a stale Method* to the
>>>> interpreter.
>>>>
>>>> *Solution
>>>> *The implementation of nmethod::do_unloading(..) is changed to clean
>>>> compiled ICs and compiled static calls if they call into a
>>>> to-interpreter stub that references dead Method* metadata.
>>>>
>>>> The patch was affected by the G1 class unloading changes (JDK-8048248)
>>>> because the method nmethod::do_unloading_parallel(..) was added. I
>>>> adapted the implementation as well.
>>>> *
>>>> Testing
>>>> *Failing test (runThese)
>>>> JPRT
>>>>
>>>> Thanks,
>>>> Tobias
>>>>
>>>> [1] see CompiledStaticCall::emit_to_interp_stub(..)
>>>> [2] see nmethod::verify_metadata_loaders(..),
>>>> static_stub_reloc()->clear_inline_cache() clears the stub
>>
>