RFR: 8268638: semaphores of AsyncLogWriter may be broken when JVM is exiting. [v4]

[David Holmes]

On Tue, 15 Jun 2021 06:19:15 GMT, Xin Liu <xliu at openjdk.org> wrote:

>> All 3 semaphores used by AsyncLogWriter are static member data. CRT(`libsystem_c.dylib __cxa_finalize_ranges`) deletes them on MacOS. Currently, AsyncLog Thread doesn't exit at all. As a result, semaphore_wait/signal
>> returns with KERN_INVALID_NAME(15) After those semaphore are destroyed. 
>> 
>> This patch change those to regular data members. This prevents from deleting.
>> This patch also provides a general RAII class AsyncLogLocker which is analogous MutexLocker.
>
> Xin Liu has updated the pull request incrementally with one additional commit since the last revision:
> 
>   Do not do sanity check for AsyncLogLocker

src/hotspot/share/logging/logAsyncWriter.cpp line 36:

> 34:  public:
> 35:   AsyncLogLocker(Semaphore* sem): _sem(sem) {
> 36:     _sem->wait();

This class is not general purpose. It does not need to accept an arbitrary semaphore. There is only one semaphore this class works with and that is AsyncLogWriter::_instance->_lock, so it can just use it directly.

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PR: https://git.openjdk.java.net/jdk/pull/4479