RFR: 8267926: AsyncLogGtest.java fails on assert with: decorator was not part of the decorator set specified at creation. [v2]

[Xin Liu]

On Mon, 31 May 2021 05:50:59 GMT, Xin Liu <xliu at openjdk.org> wrote:

>> The root cause of the intermittent failure is that _decorators in LogDecorations 
>> may be inconsistent with LogOutput::_decorators. It could happen when gtest disables a
>> Log output via set_log_config(TestLogFileName, "all=off").
>> 
>> Since we copy the entire logDecorations, it's reasonable to copy _decorator as well. 
>> LogDecorator is a bitmask of uiint. It's even smaller than a reference on LP64 platforms.
>> 
>> Caveat: this patch doesn't fix the race condition of update_decorators. Theorically,
>> it may still cause an error if user dynamically enrich decorators for one log output. 
>> User can't do that via dcmd VM.log because one can't change the configuration of 
>> an established output via dcmd.
>
> Xin Liu has updated the pull request incrementally with one additional commit since the last revision:
> 
>   8267926: AsyncLogGtest.java fails on assert with: decorator was not part of the decorator set specified at creation.

src/hotspot/share/logging/logConfiguration.cpp line 272:

> 270:   // After updating output's decorators, it's still safe to shrink all decorators of tagsets.
> 271:   //
> 272:   // There are 2 harzards in async logging. A flush operation guarantees to all pending messages in buffer are written

hazards...
I will update it in next revision.

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PR: https://git.openjdk.java.net/jdk/pull/4257