This makes TestLabelSystemstack much more strict, enabling it to detect
any misplacement of labels.

Unfortunately, there are several edge cases where we may not have an
obviously correct stack trace, so we generally except the runtime
package, with the exception of background goroutines that we know should
not be labeled.

For #50007
For #50032

Change-Id: I8dce7e7da04f278ce297422227901efe52782ca0
Reviewed-on: https://go-review.googlesource.com/c/go/+/369984
Trust: Michael Pratt <mpratt@google.com>
Run-TryBot: Michael Pratt <mpratt@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
Reviewed-by: Austin Clements <austin@google.com>

GC background mark worker goroutines are created when the first GC is
triggered (or next GC after GOMAXPROCS increases). Since the GC can be
triggered from a user goroutine, those workers will inherit any pprof
labels from the user goroutine.

That isn't meaningful, so avoid it by excluding system goroutines from
inheriting labels.

Fixes golang#50032

Change-Id: Ib425ae561a3466007ff5deec86b9c51829ab5507
Reviewed-on: https://go-review.googlesource.com/c/go/+/369983
Reviewed-by: Austin Clements <austin@google.com>
Trust: Michael Pratt <mpratt@google.com>
Run-TryBot: Michael Pratt <mpratt@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>

This makes TestLabelSystemstack much more strict, enabling it to detect
any misplacement of labels.

Unfortunately, there are several edge cases where we may not have an
obviously correct stack trace, so we generally except the runtime
package, with the exception of background goroutines that we know should
not be labeled.

For golang#50007
For golang#50032

Change-Id: I8dce7e7da04f278ce297422227901efe52782ca0
Reviewed-on: https://go-review.googlesource.com/c/go/+/369984
Trust: Michael Pratt <mpratt@google.com>
Run-TryBot: Michael Pratt <mpratt@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
Reviewed-by: Austin Clements <austin@google.com>