RFR: 8284632: runtime/Thread/StopAtExit.java possibly leaking memory again

[David Holmes]

On Thu, 28 Apr 2022 07:51:15 GMT, Robbin Ehn <rehn at openjdk.org> wrote:

>> Throwing async exceptions at exiting JavaThreads can leak the exception:
>> 
>> 1) HandshakeOperation::do_handshake() recognizes that the target thread
>>     might be terminated, but needs to do some cleanup when the operation
>>     is one that installs an async exception.
>> 
>> 2) JavaThread::exit() uses a NoAsyncExceptionDeliveryMark to protect the
>>     VM's call out to Thread::exit() from async exceptions, but it needs to do
>>     some cleanup when those async exceptions cannot be delivered because
>>     the target thread has logically exited.
>> 
>> Also tweaked runtime/Thread/StopAtExit.java to alternate between throwing
>> RuntimeException and ThreadDeath. The async exception queuing code accepts
>> any exception, but it recognizes ThreadDeath as special. When a target thread
>> already has a queued async ThreadDeath exception, then another exception will
>> not be queued. So the test now throws RuntimeException on odd iterations and
>> ThreadDeath on even iterations and the target thread will have at most two async
>> exceptions queued up.
>> 
>> This fix has been tested with Mach5 Tier[1-7] (about to start a Tier8) and I also ran
>> my StressWrapper_StopAtExit.java test using {release, fastdebug, and slowdebug}
>> bits for 12 hours per config. No leaks detected. Previously, release bits would
>> fail with OutOfMemoryException in ~2 minutes with StressWrapper_StopAtExit.java.
>
> Yes, good find!
> 
> When combining the code @dcubed-ojdk, @pchilano comments and my comments in my head I was unsure if the result was doable :) So I had to write the code to make sure I was not complete wrong.
> 
> Here is a change, diff against master:
> https://github.com/openjdk/jdk/compare/master...robehn:8284161?expand=1
> Diff against this PR:
> https://github.com/dcubed-ojdk/jdk/compare/JDK-8284632...robehn:8284161?expand=1
> Commit:
> https://github.com/robehn/jdk/commit/0224ede15980006ce547de72ee0a778b10054b45
> 
> Thanks

And now I see @robehn comment doing just that. :)

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PR: https://git.openjdk.java.net/jdk/pull/8388