RFR: 8283849: AsyncGetCallTrace may crash JVM on guarantee [v3]

[David Holmes]

On Thu, 5 May 2022 12:13:18 GMT, Jaroslav Bachorik <jbachorik at openjdk.org> wrote:

>> A gist of the fix is to allow relaxed special handling of code blob lookup when done for ASGCT. 
>> 
>> Currently, a guarantee will fail when we happen to hit a zombie method which is still on stack. While this would indicate a serious error for the normal execution flow, in case of ASGCT being in progress when the executing thread can be expected at any possible method this is something which may happen and we really should not take the profiled JVM down due to it.
>> 
>> <hr>
>> Unfortunately, I am not able to create a simple reproducer for the crash other that testing in our production where the crash is happening sporadically.
>> However, thanks to @parttimenerd and his [ASGCT stress test](https://github.com/parttimenerd/asgct2-tester.git) the problem can be reproduced quite reliably.
>> 
>> <br><br>
>> 
>> _Note: This is a followup PR for #8061_
>
> Jaroslav Bachorik has updated the pull request incrementally with one additional commit since the last revision:
> 
>   Naming and comments cleanup

Changes requested by dholmes (Reviewer).

src/hotspot/share/runtime/thread.hpp line 649:

> 647:  // support AGCT
> 648:  private:
> 649:   bool _in_agct;

This should actually be in JavaThread as AGCT only operates on JavaThreads.

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PR: https://git.openjdk.java.net/jdk/pull/8549