RFR: 8322962: Upcall stub might go undetected when freezing frames

[Martin Doerr]

On Thu, 22 Feb 2024 14:28:18 GMT, Patricio Chilano Mateo <pchilanomate at openjdk.org> wrote:

> Please review this simple fix. There is a missing push_cont_fastpath()/pop_cont_fastpath() around the call to Java in the upcall stub. Because of this, if from that upcall a virtual thread tries to yield, and all the other methods in the stack are compiled, we will incorrectly take the freeze fast path and freeze everything in the stack including the native frames. By forcing the slow path instead we will identify the upcall stub and pin the vthread.
> 
> The issue can be easily reproduced by running the modified version of test GetStackTraceALotWhenPinned.java included in this patch. I also tested the fix by running tiers1-3 in mach5. 
> 
> Thanks,
> Patricio

LGTM. Test is passing on linux PPC64le.

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Marked as reviewed by mdoerr (Reviewer).

PR Review: https://git.openjdk.org/jdk/pull/17964#pullrequestreview-1898269354