Update RAS documentation regarding Hidden frames

[fengxue-IS]

Issue or pull request number:
eclipse-openj9/openj9#14688

Overview:
Code change updated the stacktrace logic on processing Hidden frames, they are only skipped in getStackTrace calls and StackWalker API based on -XX:[+|-]ShowHiddenFrames option, RAS triggers will not be affected by the use of -XX:[+|-]ShowHiddenFrames option and alway show hidden frames to the filter

Release target:
E.g. Eclipse OpenJ9 0.31.0

Applies to the following JDK versions:
all

Applies to the following platforms:
all

[gacholio]

This applies from 0.31 onwards.

[doveye]

@fengxue-IS I assume no doc updates have been done for this issue? (I can't see any.)
Sounds like updates are required in https://eclipse-openj9.github.io/openj9-docs/xxshowhiddenframes/ and also https://eclipse-openj9.github.io/openj9-docs/version0.31/. The ID team can make these updates.

[fengxue-IS]

Yes, I haven't had time to write the doc update for this issue.
As -XX:[+|-]ShowHiddenFrames is also added as part of 0.31, update to https://eclipse-openj9.github.io/openj9-docs/version0.31/ may not be needed
It would be really appreciated if the ID team can make them. Thanks

[doveye]

@fengxue-IS I did some more digging into this item and have some comments/questions:

1. It looks like we're supporting/reimplementing the HotSpot ShowHiddenFrames option. So the docs would need to change to match what we've done before, eg in https://www.eclipse.org/openj9/docs/version0.23/#support-for-openjdk-hotspot-options. We'd also need to add the option to the table in https://www.eclipse.org/openj9/docs/cmdline_migration/#compatible-options.
2. Given the above, are we "supporting" this HotSpot option or "reimplementing" it, and are there any differences in behaviour between the OpenJ9 and Hotspot versions of ShowHiddenFrames?
3. https://github.com/openjdk/jdk/blob/master/src/hotspot/share/runtime/globals.hpp lists the option as a diagnostic option and says that diagnostic options are not documented and users can enable them with guidance from support. So are we sure we want to document this option at all?

[fengxue-IS]

@doveye thanks for looking into this issue

1. we are technically reimplementing this option, and it is different from the OpenJDK option which requires use of +UnlockDiagnosticVMOptions together
2. As noted in this issue, for OpenJ9, this option is doesn't affect output of dump, (only JCL API's behave similar to RI's use for this option and other uses are not guaranteed)
3. My understanding is that we should doc it as this is a useful debug option (also since this is -XX option which already implies implementation specific) @gacholio @pshipton do you have any thoughts on this?

[pshipton]

I don't have a problem documenting the option. This type of option helps user's diagnose problems themselves without needing input from service. We could mention it's only expected to be used for diagnostics.

[gacholio]

This really isn't a diagnostic option (in fact, it should not be an option at all). If the default is to not show hidden frames. then using the option will result in failed security checks, etc, so it's almost impossible that any modern application could function.

[tajila]

Running with -XX:+ShowHiddenFrames on JDK18+ will result in functional issues. We should probably raise a bug with OpenJDK. Either they need to update the new MH implementation to work properly without hiding frames or the option needs to be removed.

[pshipton]

I think @gacholio comments are specific to jdk18+. Using the option for 8, 11, 17 restores the behaviour of previous releases so may help diagnose a problem.

[Sreekala-Gopakumar]

@fengxue-IS - Following changes have been made:

• updated the ShowHiddenFrames content (-XX:[+|-]ShowHiddenFrames topic) to mention HotSpot for consistency.
• Added that this option doesn't affect the dump file.
• Added this option to the table in the Switching to OpenJ9 topic.

Please check and let me know, if the changes are ok.

[doveye]

I've merged the PR but we didn't add any content for the Java 18 issue. If it's an OpenJDK problem then we could put it in the Known Issues table in the release notes at https://github.com/eclipse-openj9/openj9/blob/master/doc/release-notes/0.32/0.32.md. Eg:

Issue #: 14803
Description: Using the -XX:+ShowHiddenFrames option in an OpenJ9 release built with OpenJDK 18 causes errors due to underlying problems in OpenJDK
Platform: All platforms
Impact: MethodHandle frames cannot be shown in stack traces
Workaround: Avoid using the -XX:+ShowHiddenFrames option with OpenJDK 18

@tajila @pshipton @gacholio Are you happy with this please?

[pshipton]

The impact is not correct. I don't think we need to add this to mention the problems, but I'll defer to Tobi. It's already stated it's a diagnostic/debugging option.

[tajila]

Impact: MethodHandle frames cannot be shown in stack traces

The actual impact is that the wrong exception may be thrown when using Reflection API.

[doveye]

It might be a diagnostic option but if users on Java 18 use it and it breaks their app, shouldn't we warn them about that? Otherwise they could be wasting time trying to debug what's actually a known issue. Although throwing the wrong exception doesn't sound like the inability to function that Graham mentioned earlier.

[doveye]

It looks like the release notes got updated anyway, so I'll close this issue.