RFR: Add a limition to allocate object heap in aarch64 with tsan enabled.

[Jie He]

On Tue, 21 Apr 2020 18:53:46 GMT, Man Cao <manc at openjdk.org> wrote:

>> @caoman I think it's better to put the code into os_posix.cpp with TSAN_ONLY, AARCH64_ONLY, not os_linux_aarch64.cpp,
>> because latter has to make multiple copies of function has_allocatable_memory_limit for archtectures. And in
>> os_linux.cpp, AARCH64, X86_64 specific code is allowed. what do you think?
>
> Putting the code related to reasonable_max in os_posix.cpp sounds good.
> It's better to guard it with TSAN_RUNTIME_ONLY(). We would like to keep "-XX:-ThreadSanitizer" the same as the default
> JVM configuration.

no, I have to use TSAN_ONLY, otherwise, building java images will fail, where jvm has been used without
+ThreadSanitizer. In addition, some scripts like jtreg also use "java --version" or other commands without
+ThreadSanitizer to do some jobs.

I just see other functions has similar style, which define and use the Macros or const variables locally, due to merely
one use place.

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PR: https://git.openjdk.java.net/tsan/pull/6