Extra Ms can move between system threads. needm will reinitialize procid
(via minit) on the new thread, but leaving a stale procid behind after
dropm can be misleading if printing the M early in needm for debugging.
Change-Id: I668891971a0baeab31170d1e40a97126416e7379
Reviewed-on: https://go-review.googlesource.com/c/go/+/526118 Reviewed-by: Cherry Mui <cherryyz@google.com>
Auto-Submit: Michael Pratt <mpratt@google.com> Reviewed-by: Michael Knyszek <mknyszek@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>