runtime: explicitly exclude a potential deadlock in the scheduler

The following sequence in the scheduler may potentially lead to
deadlock:
- globrunqget() -> runqput() -> runqputslow() -> globrunqputbatch()
However, according to the current logic of the scheduler it is not
possible to face the deadlock.

The patch explicitly excludes the deadlock, even though it is impossible
situation at the moment.

Additionally, the "runq" and "globrunq" APIs were partially refactored,
which allowed to minimize the usage of these APIs by each other.
This will prevent situations described in the CL.

Change-Id: I7318f935d285b95522998e0903eaa6193af2ba48
Reviewed-on: https://go-review.googlesource.com/c/go/+/662216
Reviewed-by: Keith Randall <khr@golang.org>
Reviewed-by: Keith Randall <khr@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Dmitri Shuralyov <dmitshur@google.com>

0 files changed, 0 insertions, 0 deletions