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    SubjectRe: [RFC][PATCH 06/22] sched: SCHED_DEADLINE handles spacial kthreads
    On 11/11, Peter Zijlstra wrote:
    >
    > On Thu, 2010-11-11 at 16:27 +0100, Oleg Nesterov wrote:
    > >
    > > Sorry, can't resist, off-topic quiestion. Do we really need
    > > migration_call()->migrate_live_tasks() ?
    > >
    > > With the recent changes, try_to_wake_up() can never choose
    > > the dead (!cpu_online) cpu if the task was deactivated.
    > >
    > > Looks like we should only worry about the running tasks, and
    > > migrate_dead_tasks()->pick_next_task() loop seems to all work
    > > we need.
    > >
    > > (Of course, we can't just remove migrate_live_tasks(), at leat
    > > migrate_dead() needs simple changes).
    > >
    > > What do you think?
    >
    > Yes, I think we can make that work, we could even move that
    > migrate_live_tasks() into CPU_DYING, which is before this point.

    Hmm, I think you are right. In this case we can also simplify
    migrate-from-dead-cpu paths, we know that nobody can touch rq->lock,
    every CPU runs stop_machine_cpu_stop() with irqs disabled. No need
    to get/put task_struct, etc.

    Oleg.



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