[jdk16] RFR: 8257521: runtime/logging/MonitorInflationTest.java crashed in MonitorList::unlink_deflated

[Daniel D.Daugherty]

On Wed, 23 Dec 2020 12:05:58 GMT, Kim Barrett <kbarrett at openjdk.org> wrote:

>> This is a trivial fix to MonitorList::unlink_deflated() to prevent it from
>> crashing when called with an empty in-use MonitorList. That condition
>> can only arise during the final audit during VM shutdown.
>> 
>> This fix has been tested with runtime/logging/MonitorInflationTest.java
>> combined with temporary debug code that delays the background threads
>> that normally call Object.wait() very early in the VM's life. By delaying those
>> background threads, we increase the likelihood of having an empty in-use
>> MonitorList.
>> 
>> The fix has also been tested with Mach5 Tier[1-3].
>
> Looks good, and agree the fix is trivial (though the analysis to get there is not trivial at all; thanks for the info in the bug report).

@kimbarrett - Thanks for the review!

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PR: https://git.openjdk.java.net/jdk16/pull/62