RFR: 8273456: Do not hold ttyLock around stack walking

[Erik Österlund]

On Thu, 9 Sep 2021 14:54:01 GMT, Coleen Phillimore <coleenp at openjdk.org> wrote:

> This change moves the tty rank back down to near access, and prints stack traces to stringStream to avoid holding the tty lock while trying to take the stackwatermark lock.
> Tested with tier1-8 (7,8 still in progress but no failures so far).

Looks good.

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Marked as reviewed by eosterlund (Reviewer).

PR: https://git.openjdk.java.net/jdk/pull/5445