runtime: don't hold the table lock in (*traceStackTable).dump
There's a conceptual cycle between traceStackTable.lock and
allocation-related locks, but it can't happen in practice because the
caller guarantees that there are no more writers to the table at the
point that dump is called.
But if that's true, then the lock isn't necessary at all. It would be
difficult to model this quiesence in the lockrank mode, so just don't
hold the lock and expand the documentation of the dump method.
Change-Id: Id4db61363f075b7574135529915e8bd4f4f4c082
Reviewed-on: https://go-review.googlesource.com/c/go/+/544177 Reviewed-by: Matthew Dempsky <mdempsky@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com> Reviewed-by: Cherry Mui <cherryyz@google.com>