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    SubjectRe: [PATCH 1/1] hotplug cpu: migrate a task within its cpuset

    * Cliff Wickman <> wrote:

    > With this patch, migrate the task to:
    > 1) to any cpu on the same node as the disabled cpu, which is both online
    > and among that task's cpus_allowed
    > 2) to any online cpu within the task's cpuset
    > 3) to any cpu which is both online and among that task's cpus_allowed
    > Diffed against 2.6.21-rc3 (Andrew's current top of tree)

    looks good to me.

    Acked-by: Ingo Molnar <>

    > + /* try to stay on the same cpuset */
    > + if (dest_cpu == NR_CPUS) {
    > + p->cpus_allowed = cpuset_cpus_allowed(p);
    > + dest_cpu = any_online_cpu(p->cpus_allowed);
    > + }

    what's the practical effect of this - when moving the last CPU offline
    from a node you got jobs migrated to really alien nodes? Thus i think we
    should queue this up for v2.6.21 too, correct? It's a NOP on systems
    that do not set up cpusets, so it's low-risk.

    btw., unrelated to your patch, there's this bit right after the code

    /* No more Mr. Nice Guy. */
    if (dest_cpu == NR_CPUS) {
    rq = task_rq_lock(p, &flags);
    dest_cpu = any_online_cpu(p->cpus_allowed);

    out of consistency, shouldnt the cpus_setall() rather be:

    p->cpus_allowed = cpu_possible_map;

    ? It shouldnt make any real difference but it looks more consistent.

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