RFR: 8258032: Reconsider LEAF entry restrictions [v2]

Wed Jan 13 15:27:05 UTC 2021

On Fri, 8 Jan 2021 13:54:11 GMT, Coleen Phillimore <coleenp at openjdk.org> wrote:

>> JRT_LEAF still has a NoSafepointVerifier if that helps.  There's a comment about the things it's not allowed to do in interfaceSupport.inline.hpp.  The things it's not supposed to do are all checked by the NSV.
>> One of the things it can do now (especially if it's not going to safepoint) is to have a Handle with an enclosing HandleMark because GC won't touch the oops anyway.  This is one of the things @pron ran into with loom (see issue) and @fisk and I discussed.
>> I originally took the bug because I was going to close it as WNF, because I hate removing restrictions.
>> I do think there is a bug lurking here.  If you have a Handle without an enclosing HandleMark in JRT_LEAF, it will not be cleaned up when the leaf function returns.  This might need a HandleMarkCleaner.
>
> I do not see fetch_unroll_info_helper reverting back to JRT_LEAF.

I am closing this as WNF.  There are too many problems that you can get into if you're not careful.
I opened a new issue to fix the wrong comments in deoptimization.cpp.

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PR: https://git.openjdk.java.net/jdk/pull/1990