RFR: 8255678: Add Mutex::try_lock version without rank checks [v2]

[Patricio Chilano Mateo]

On Thu, 19 Nov 2020 03:07:04 GMT, Coleen Phillimore <coleenp at openjdk.org> wrote:

>> Patricio Chilano Mateo has updated the pull request incrementally with one additional commit since the last revision:
>> 
>>   address Dan's comments
>
> src/hotspot/share/runtime/mutex.cpp line 400:
> 
>> 398:   if (owned_by_self()) {
>> 399:     // wait() case
>> 400:     Mutex* least = get_least_ranked_lock_besides_this(locks_owned);
> 
> Wouldn't you want to test check_can_be_skipped before all this code and skip all of this?

For the wait() case, today we always check that the thread doesn't wait while holding a Mutex/Monitor of rank less than or equal to special, and I didn't want to change that.
But I could do it for the "lock()/lock_without_safepoint_check()/try_lock()" case, and return before calling get_least_ranked_lock().

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PR: https://git.openjdk.java.net/jdk/pull/1242