[PATCH 0/4] sched: Fix hot-unplug regressions

[Peter Zijlstra]

Hi,

These 4 patches are the simplest means (barring a revert) of fixing the CPU
hot-unplug problems introduced by commit:

  1cf12e08bc4d ("sched/hotplug: Consolidate task migration on CPU unplug")

Testing here, any by Paul, indicate they survive a pounding.

They restore the previous behaviour of forced affinity breaking for the class
of kernel threads that happen to have single CPU affinity, but are not strictly
a per-cpu kthread.