RFR: 8268164: Adopt cast notation for WorkerThread conversions

[Albert Mingkun Yang]

On Thu, 3 Jun 2021 22:33:32 GMT, David Holmes <david.holmes at oracle.com> wrote:

> For JavaThread we have a const and non-const version (not sure why though).

`as_Java_thread` is called with `const Thread*` in two places, listed below. The criteria of having a `const Thread*`-version cast method hinges on the caller, whether it has a `const Thread*` and/or wants a `const XThread*` in return. `as_Java_thread` is called both with and with `const`, while `XThread* cast(Thread* t)` is enough for others currently.


traceid JfrThreadId::id(const Thread* t);

const char* JfrThreadName::name(const Thread* t);

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PR: https://git.openjdk.java.net/jdk/pull/4334