RFR: 8267517: async logging for stdout and stderr [v3]

[Xin Liu]

On Tue, 21 Dec 2021 05:56:39 GMT, David Holmes <dholmes at openjdk.org> wrote:

>> Xin Liu has updated the pull request incrementally with one additional commit since the last revision:
>> 
>>   Fix typo and the building eror on MacOS.
>
> Sorry Xin, the test is timing out on Linux-x64. There's no information to diagnose any problems though.
> 
> David

hi, @dholmes-ora , 

I come up an idea to prove that -Xlog:async at work. In gtest `test_asynclog.cpp`, I use `testing::internal::GetCapturedStdout/err()` to get the contents of stdout/err. Only AsyncLog will drop messages because of the buffer size.  freopen is simpler, however I found "freopen(TestLogFileName, stdout)` would mess with other testsuites because all TEST_VM_F run in a same process. 

In this revision,  write_blocking() has flushing semantic for both LFO and LFSO.  Could you take a look?

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PR: https://git.openjdk.java.net/jdk/pull/6132