RFR: 8275049: [ZGC] missing null check in ZNMethod::log_register

[Martin Doerr]

On Mon, 11 Oct 2021 12:23:03 GMT, Martin Doerr <mdoerr at openjdk.org> wrote:

> The VM crashes while trying to read (*p)->klass() in "ZNMethod::log_register" on PPC64. We need a null check. See JBS for details.

Hi Erik,
your description sounds like the plain reads are what are problematic. (Oop creation always needs to release the header initialization. Otherwise, it's a bug there.) I agree with that. I could use `Atomic::load(p)` or `Atomic::load_acquire(p)`. What do you think about that?
Fundamental locking changes are out of scope, here. That could be done separately if desired. This issue is about the missing null check. Note that we may need to backport this fix, so we should better keep it simple.

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PR: https://git.openjdk.java.net/jdk/pull/5892