RFR[JDK11]: 8204691: HeapRegion.apply_to_marked_objects_other_vm_test fails with assert(!hr->is_free() || hr->is_empty()) failed: Free region 0 is not empty for set Free list #

[Erik Helin]

On 07/08/2018 05:52 PM, Kim Barrett wrote:
>> On Jul 5, 2018, at 4:03 PM, Kim Barrett <kim.barrett at oracle.com> wrote:
>>
>>> On Jul 5, 2018, at 3:57 AM, Thomas Schatzl <thomas.schatzl at oracle.com> wrote:
>>>
>>> Hi,
>>>
>>> On Wed, 2018-07-04 at 20:13 -0400, Kim Barrett wrote:
>>>> Please review this fix of the HeapRegion gtest.
>>>>
>>>> The test modifies a region's "top" to unexpected values without
>>>> ensuring that no allocation might use the region and no GC might run
>>>> while the region is in that invalid state.  We solve this by
>>>> executing the test code in its very own safepoint, and by saving and
>>>> then restoring the region's top back to its original value before
>>>> completing the test.  And since we are doing all that, there's no
>>>> longer any reason to run the test in a separate VM.
>>>
>>> looks good, but the actual test is still run in a separate VM.
>>> Intentional?
>>
>> Unintentional. And now I’m not sure what I last ran through mach5.
>> I’ll re-test with TEST_OTHER_VM => TEST_VM.
>>
>> I know that failed in an obscure way earlier, but I think that was because
>> of an unrelated recently introduced bug that’s been fixed in the repo.
> 
> Verified that I really have tested in same VM.  New webrev:
> http://cr.openjdk.java.net/~kbarrett/8204691/open.01/
> 
> The only change is TEST_OTHER_VM => TEST_VM.

Hmmm, it is (very) unfortunate if we have native code in JVM allocating 
Java objects and triggering garbage collections _concurrently_ with the 
unit tests being run (there shouldn't be any Java code running when the 
unit tests are executing). I understand that we have to restore the top 
pointer in case there is some verification for example when the JVM 
exits (or if we assert in a destructor etc), but do we really need to 
run the test in a safepoint? There is nothing wrong with running the 
test in a safepoint, but it seems to me that we then would have to run 
almost all TEST_VM tests in a safepoint?

Thanks,
Erik