RFR: 8325937: runtime/handshake/HandshakeDirectTest.java causes "monitor end should be strictly below the frame pointer" assertion failure on AArch64 [v2]

[Robbin Ehn]

On Thu, 3 Oct 2024 11:54:53 GMT, Coleen Phillimore <coleenp at openjdk.org> wrote:

>> Add missing StoreLoad fences in handshaking code to match safepoint code.  Thanks to @pchilano for finding this bug.
>> 
>> Tested with tier1-4 and tier8 which has Kitchensink in it.
>
> Coleen Phillimore has updated the pull request incrementally with one additional commit since the last revision:
> 
>   Remove comment about state.

> > What I wrote here: [#21295 (comment)](https://github.com/openjdk/jdk/pull/21295#issuecomment-2390081948) (I hope that explains it)
> 
> Sorry if I'm being dense but no. This is about the StackWaterMark processing code?

Before going into the handshake code we do other things (SWM is one of those).
This code that 'happens before' is not intended to be re-ordered with the set blocked state.
So I have a hard time reason about it and prefer we add a fence to avoid this un-intended re-ordering.

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PR Comment: https://git.openjdk.org/jdk/pull/21295#issuecomment-2392420129