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

[Per Liden]

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.

src/hotspot/share/gc/z/zNMethod.cpp line 130:

> 128:     for (oop* p = begin; p < end; p++) {
> 129:       const char* external_name = (*p) == nullptr ? "null"
> 130:                                                   : (*p)->klass()->external_name();

Apart from doing an Atomic::load() here, I'd also suggest we write "N/A" instead of "null", since the class isn't really null.

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