RFR: 8263017: Read barriers are missing in nmethod printing code

[Erik Österlund]

On Thu, 11 Mar 2021 21:05:51 GMT, Vladimir Ivanov <vlivanov at openjdk.org> wrote:

> > The load barrier on misaligned oop relocations will cause intermittent crashes. This is not safe. I can give you a fix tomorrow hopefully.
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> Thanks, Erik. 
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> As an alternative, I could add `BarrierSetNMethod::nmethod_entry_barrier()` into `nmethod::print_nmethod()` to ensure that all the oops are healed. Let me know what you prefer.

You can run nmethod::run_nmethod_entry_barriers() for now to fix the immediate bug. Then I can add the better load barrier for this situation. If you decide to do that, consider this reviewed.

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PR: https://git.openjdk.java.net/jdk/pull/2919