Speaking about helpers, could we also add kthread_start(), which should be
used instead of direct wake_up_process() ? Not that it is terribly important,
but still.
Note that "kthread_create() pins the task_struct" allows us to cleanup the code.
Look at this ugly "wait_to_die:" label in migration_thread(). Is is because
migration_thread() can't exit until CPU_DEAD reaps it. Other reasons were already
solved by kthread-enhance-kthread_stop-to-abort-interruptible-sleeps.patch
Oleg.
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