Integrated: 8298371: monitors_on_stack extracts unprocessed oops

[Stefan Karlsson]

On Thu, 8 Dec 2022 10:27:31 GMT, Stefan Karlsson <stefank at openjdk.org> wrote:

> While investigating JDK-8298058 we've found that monitors_on_stack extracts oops without setting up the RegisterMap to process oops. This then leaks out stale oops.
> 
> A simple fix is to change the RegisterMap to perform oops processing. However, monitors_on_stack is only used in an assert, so this means that we'll get a difference in behavior between release builds and debug builds. This has the potential to hide bugs in debug builds. It has been suggested to me that it might be better to simply remove the assert:
> 
>   assert(monitors_on_stack(current) == ((current->held_monitor_count() - current->jni_monitor_count()) > 0),
>          "Held monitor count and locks on stack invariant: " INT64_FORMAT " JNI: " INT64_FORMAT, (int64_t)current->held_monitor_count(), (int64_t)current->jni_monitor_count());
> 
> 
> The suggested patch just turns on processing, but I'm also fine with removing the assert if that seems to be a better solution.
> 
> Tested with reproducer using Fuzz.java + ZGC

This pull request has now been integrated.

Changeset: b754aa5e
Author:    Stefan Karlsson <stefank at openjdk.org>
URL:       https://git.openjdk.org/jdk/commit/b754aa5e3f231aea8da5274c330dc55dd78b0f67
Stats:     1 line in 1 file changed: 0 ins; 0 del; 1 mod

8298371: monitors_on_stack extracts unprocessed oops

Reviewed-by: pchilanomate, rehn

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PR: https://git.openjdk.org/jdk/pull/11582