RFR: 8273831: PrintServiceLookup spawns 2 threads in the current classloader, getting orphaned

[Alexey Ivanov]

On Thu, 14 Oct 2021 05:43:53 GMT, Sergey Bylokhov <serb at openjdk.org> wrote:

> The PrintServiceLookupProvider can spawn 2 threads on WIndows and one thread on Linux. These threads are connected to the classloader of the web application.  During undeployment the app classloader gets removed together with the two orphaned threads by the Tomcat. 
> 
> Looks like the tomcat has special machinery to workaround such threads:
> https://cwiki.apache.org/confluence/display/tomcat/MemoryLeakProtection#MemoryLeakProtection-cclThreadSpawnedByJRE
> But it should be updated each time we add/update/rename the threads in the JDK. So JreMemoryLeakPreventionListener can be updated to solve this problem, but it will be good to reset the ref to the app class loader as we usually do for our internal threads. 
> 
> The change updates threads to use the root thread group and null context class loader.
> 
> A similar pattern is used here:
> https://github.com/openjdk/jdk/blob/6765f902505fbdd02f25b599f942437cd805cad1/src/java.desktop/share/classes/com/sun/imageio/stream/StreamCloser.java#L89
> 
> @aivanov-jdk please take a look

Marked as reviewed by aivanov (Reviewer).

Sorry for my delayed review, looks good to me.

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PR: https://git.openjdk.java.net/jdk/pull/5939