RFR: 8255131: G1CollectedHeap::is_in() returns wrong result

[Stefan Johansson]

On Thu, 22 Oct 2020 11:01:53 GMT, Kim Barrett <kbarrett at openjdk.org> wrote:

>> Hi all,
>> 
>>   please review this change to exchange the broken G1CollectedHeap::is_in() by G1CollectedHeap::is_in_exact() that has the same performance profile and correct.
>> 
>> G1CollectedHeap::is_in() returns true for any region ever committed (and crashes for not yet committed regions), while is_in_exact() (almost) did the right thing. Almost because HeapRegionManager::is_available() would assert if the given pointer is outside the heap and it's not guarded by is_in_reserved.
>> 
>> Test: tier1
>> 
>> Thanks,
>>   Thomas
>
> src/hotspot/share/gc/g1/g1CollectedHeap.cpp line 2264:
> 
>> 2262: bool G1CollectedHeap::is_in(const void* p) const {
>> 2263:   if (is_in_reserved(p) &&
>> 2264:     _hrm->is_available(addr_to_region((HeapWord*)p))) {
> 
> This line is misindented.  But rather than adjusting the indentation, how about instead changing the function to
> bool G1CollectedHeap::is_in(const void* p) const {
>   return is_in_reserved(p) && _hrm->is_available(addr_to_region((HeapWord*)p));
> }

I was thinking something similar, so I would approve going with this proposal.

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PR: https://git.openjdk.java.net/jdk/pull/799