RFR: 8254877: GCLogPrecious::_lock rank constrains what locks you are allowed to have when crashing [v2]

[Albert Mingkun Yang]

On Thu, 29 Oct 2020 09:34:12 GMT, Stefan Karlsson <stefank at openjdk.org> wrote:

>> src/hotspot/share/gc/shared/gcLogPrecious.cpp line 30:
>> 
>>> 28: stringStream* GCLogPrecious::_lines = NULL;
>>> 29: stringStream* GCLogPrecious::_temp = NULL;
>>> 30: Semaphore* GCLogPrecious::_lock = NULL;
>> 
>> Maybe renaming `_lock` to `_semaphore`? Additionally, since it's a binary semaphore, `new Semaphore(1)`, some comments explaining why `Mutex` is **not** suitable could avoid some future confusions.
>> 
>> PS: not a review, just a comment in passing.
>
> It's used as a lock, so I think the name `_lock` is appropriate. Instead I introduced a new class: `SemaphoreLock`, to make the code more readable (IMHO). Also added a comment. Hopefully, this addressed your comments.

Thank you; it does look more readable. BTW, mutex has `try_lock` as well.

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PR: https://git.openjdk.java.net/jdk/pull/903