RFR(M): 8239024: Kitchensink24HStress.java failed due to timeout

[Erik Gahlin]

Looks good. 

Erik

> On 10 Jun 2020, at 19:11, Markus Gronlund <markus.gronlund at oracle.com> wrote:
> 
> Greetings,
> 
> Please review this fix to resolve a deadlock involving the JfrStream_lock.
> 
> Bug: https://bugs.openjdk.java.net/browse/JDK-8239024 
> Webrev: http://cr.openjdk.java.net/~mgronlun/8239024/webrev00/
> Testing: jdk_jfr
> 
> This webrev is a diff against https://mail.openjdk.java.net/pipermail/hotspot-jfr-dev/2020-June/001513.html 
> 
> Please see the full problem description in the bug.
> 
> Short comment:
> The JfrRotationLock is only used by a single thread (the JFR Recorder Thread) during normal operations. Its only purpose is to provide a mutex for a potential JFR Emergency dump thread corrupting in-flight serializations as part of crash dumps. Previously, this lock provided a slow path to have a JavaThread wait on the JfrMsg_lock (so that safepoints could proceed). But with the changes associated with JDK-8245113, these threads are now in state _thread_in_native, so this wait is replaced by a simple os::naked_short_sleep().
> 
> Thanks to Robbin Ehn for problem analysis.
> 
> Thanks
> Markus