RFR: 8313798: [aarch64] sun/tools/jhsdb/HeapDumpTestWithActiveProcess.java sometimes times out on aarch64

[Chris Plummer]

On Thu, 10 Aug 2023 18:11:02 GMT, Andrew Haley <aph at openjdk.org> wrote:

> I wonder what triggers this problem. Maybe there's an underlying bug, or maybe it's just to do with AArch64's weakly-consistent memory model.

Yes, you are correct, and I already filed [JDK-8313800](https://bugs.openjdk.org/browse/JDK-8313800). As noted in this [JDK-8313800](https://bugs.openjdk.org/browse/JDK-8313800), you really shouldn't ever see issues at this point in the stack walk:

>   Note, usually stack walking issues with an active thread are with the topmost frame (the first frame that is visited), because it might be in an inconsistent state (not fully pushed or popped). If the state of the first frame is valid, then walking the rest of the stack should have no issues. But in all the above cases we eventually run into an issue with a frame higher up the stack, so this suggests that the stack walking code is broken in certain situations. Basically there is a frame somewhere in the middle of the stack that the stack walking code doesn't know how to get past. This seems to be unique to aarch64. 

This could be SA not understanding how to properly walk the frame. For example, maybe an issue like [JDK-8247351](https://bugs.openjdk.org/browse/JDK-8247351), which has been fixed.

That being said, the fix for this PR is still warranted because it could happen if the first frame is not in a valid state.

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PR Comment: https://git.openjdk.org/jdk/pull/15183#issuecomment-1673739839