For obvious performance reasons, scheduler state changes (other than
aborting a thread) do not cause synchronous interrupts on the other
CPU. Doing a k_thread_wakeup() means that the current CPU will run it
synchronously if it's high priority, but if you want to see it run on
the other cores you need to wait for them to reach a scheduling point
on their own.
The test was written to assume that k_thread_wakeup() is synchronous,
but that's not right, and it needs to spin a bit. This bug was always
present in the test, but masked by a bug in the way that k_sleep() was
handled on SMP. See #9506.
Signed-off-by: Andy Ross <andrew.j.ross@intel.com>
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